MVVM datagrid comboboxes are not displaying the initial values and the moderator dropdown list needs to be unique

Yvon 50

Based on my last request from this community and I got the POC working.

[https://learn.microsoft.com/en-us/answers/questions/1571452/how-to-save-all-the-updates-in-a-datagrid-(set-of?page=4&orderby=helpful#answers](https://learn.microsoft.com/en-us/answers/questions/1571452/how-to-save-all-the-updates-in-a-datagrid-(set-of?page=4&orderby=helpful#answers)

I start associate with the real work.

I continue use student dataset as guideline.

My schema: 2 tables (Moderators and ModeratorType)

Moderators is table containing data to be manipulated. While ModeratorType is overloading table serves as lookup.

The question: (Moderator datagrid) The drop down comboboxes are not showing the initial values? The Student datagrid is working fine.

Here is my codes and schema

insert Moderators values ('1234','Plastic','<30')

insert Moderators values ('1234','Water','Hot')

insert Moderators values ('1234','Water','Code')

insert Moderators values ('4567','Metal','Silver')

ModeratorType is just a lookup table

insert ModeratorType values ('Plastic','p','<=50');

insert ModeratorType values ('Plastic','p','>50');

insert ModeratorType values ('Plastic','p','=100');

insert ModeratorType values ('Water','w','Hot');

insert ModeratorType values ('Water','w','Cold');

insert ModeratorType values ('Metal','m','Silver');

insert ModeratorType values ('Metal','m','Gold');

I create a new UserControl2.xaml and similar to UserControl1.xaml Except the schema different.

But somehow the datagrid combobox didn't display the initial values

Tried so many SelectedValue/SelectedValuePath/SelectedItem, and still not displaying initial values

Plus I want the drop down combobox (material column) returns unique instead repeating (eg: Plastic)

User's image

Yvon 50

<Window x:Class="WpfSimple_v2.Window003"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfSimple_v2.ViewModels"
         xmlns:uc="clr-namespace:WpfSimple_v2"
        mc:Ignorable="d"
        Title="Window003" Height="608.553" Width="871.641">
    <Window.Resources>
        <local:ViewModelMain x:Key="vm"/>
    </Window.Resources>
    <Grid DataContext="{StaticResource vm}" Margin="10">
        <Grid.Resources>
            <Style TargetType="Button">
                <Setter Property="Margin" Value="10"/>
                <Setter Property="Width" Value="150"/>
                <Setter Property="Height" Value="25"/>
                <Setter Property="VerticalAlignment" Value="Top"/>
            </Style>
        </Grid.Resources>
        <Grid.RowDefinitions>
            <RowDefinition Height="auto"/>
            <RowDefinition Height="76.8"/>
            <RowDefinition Height="auto" MinHeight="36"/>
            <RowDefinition Height="353.6"/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition Width="220"/>
        </Grid.ColumnDefinitions>
        <Label Grid.Row="0" Grid.Column="0" Content="TeacherAddress" Margin="5,5,5.8,5"/>
        <uc:PlacesDataGrid Grid.Row="1" Grid.Column="0" Margin="5,5,5.8,71.8"
                       DataGridItemsSource="{Binding AllTeachers}"/>
        <Button Grid.Row="1" Grid.Column="1" Margin="4.2,5,0,0" Width="150" HorizontalAlignment="Left"
            Content="AddTeacher" 
            Command="{Binding Cmd}" CommandParameter="AddTeacher"/>

        <Label Grid.Row="2" Grid.Column="0" Content="StudentAddress" Margin="5,5.2,5.8,4.8"/>
        <uc:PlacesDataGrid Grid.Row="2" Grid.Column="0" Margin="13,32.2,10.8,5.4"
                       DataGridItemsSource="{Binding AllStudents}" Grid.RowSpan="2" RenderTransformOrigin="0.511,0.39"/>
        <Button Grid.Row="3" Grid.Column="1"  Margin="4.2,5.2,0,0" Width="150" HorizontalAlignment="Left"
            Content="AddStudentAddress"
            Command="{Binding Cmd}" CommandParameter="AddStudent"/>

        <Label Grid.Row="3" Grid.Column="0" Content="Moderator" Margin="13,181.2,5.8,4.4"/>
        <uc:UserControl2 Grid.Row="2" Grid.Column="0" Margin="13,32.2,218.8,5.4"
                       DataGridItemsSource2="{Binding AllModerators}" Grid.RowSpan="2" Grid.ColumnSpan="2" RenderTransformOrigin="0.511,0.39"/>
        <Button Grid.Row="3" Grid.Column="1"  Margin="4.2,242.2,0,0" Width="150" HorizontalAlignment="Left"
            Content="AddModerator"
            Command="{Binding Cmd}" CommandParameter="AddModerator"/>

        <StackPanel Grid.Row="4" Grid.ColumnSpan="2" HorizontalAlignment="Right" Orientation="Horizontal" Margin="0,1.6,0.8,13" Width="320" >
            <Button Content="CancelAll" Command="{Binding Cmd}" CommandParameter="CancelAll" Margin="5,2,5,0"/>
            <Button Content="SaveAll" Command="{Binding Cmd}" CommandParameter="SaveAll" Margin="5,2,5,0"/>
        </StackPanel>
    </Grid>
</Window>

Yvon 50

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using WpfSimple_v2.Models;

namespace WpfSimple_v2
{
    public class DAL
    {



        
        private static CDataSet ds;
        public void LoadData()
        {
            ds = new CDataSet();


            using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Moderators where partnumber = '1234'", ConnString)) da.Fill(ds.Moderators);
            using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM ModeratorType", ConnString)) da.Fill(ds.ModeratorType);




            //using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM PlacesOfInterest", ConnString)) da.Fill(ds.PlacesOfInterest);
            //using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Teachers", ConnString)) da.Fill(ds.Teachers);
            using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Students", ConnString)) da.Fill(ds.Students);
            using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Countries", ConnString)) da.Fill(ds.Countries);
            using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Provinces", ConnString)) da.Fill(ds.Provinces);
            using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Districts", ConnString)) da.Fill(ds.Districts);
            /*
			ds.Teachers.RowChanged += (sender, e) =>
			{
				if (e.Action == DataRowAction.Change)
				{
					Window003DS.TeachersRow row = e.Row as Window003DS.TeachersRow;
					if (ProvincesByCountry(row).Where((p) => p.ProvinceID == row.ProvinceID).FirstOrDefault() == null && row.ProvinceID != 0) row.ProvinceID = 0;
					if (DistrictsByProvinceID(row).Where((p) => p.DistrictID == row.DistrictID).FirstOrDefault() == null && row.DistrictID != 0) row.DistrictID = 0;
				}
			};
			*/
            ds.Moderators.RowChanged += (sender, e) =>
            {
                if (e.Action == DataRowAction.Change)
                {
                    CDataSet.ModeratorsRow row = e.Row as CDataSet.ModeratorsRow;
                    if (MassByModerator(row).Where((p) => p.Mass == row.Mass).FirstOrDefault() == null && row.Mass != null) row.Mass = "";

                    if (ModeratorByMaterial(row).Where((p) => p.Moderator == row.Material).FirstOrDefault() == null && row.Material != null) row.Material = "";

              
                }
            };

            ds.Students.RowChanged += (sender, e) =>
            {
                if (e.Action == DataRowAction.Change)
                {
                    CDataSet.StudentsRow row = e.Row as CDataSet.StudentsRow;
                    if (ProvincesByCountry(row).Where((p) => p.ProvinceID == row.ProvinceID).FirstOrDefault() == null && row.ProvinceID != 0) row.ProvinceID = 0;
                    if (DistrictsByProvinceID(row).Where((p) => p.DistrictID == row.DistrictID).FirstOrDefault() == null && row.DistrictID != 0) row.DistrictID = 0;
                }
            };


        }
        //internal object GetTeachers() => ds.Teachers;
  
        //internal void AddTeacher() => ds.Teachers.Rows.Add(ds.Teachers.NewRow());
       // internal void AddStudent() => ds.Students.Rows.Add(ds.Students.NewRow());
        internal object GetStudents() => ds.Students;
        internal void AddStudent() => ds.Students.Rows.Add(ds.Students.NewRow());

        internal object GetModerators() => ds.Moderators;
        internal void AddModerators()
        {
            ds.Moderators.Rows.Add(ds.Moderators.NewRow());
        }
        internal void SaveAll()
        {
            /*
			using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Teachers", ConnString))
			{
				SqlCommandBuilder cb = new SqlCommandBuilder(da);
				da.MissingSchemaAction = MissingSchemaAction.AddWithKey;
				da.RowUpdated += OnRowUpdated;
				da.Update(ds.Teachers);
			
			} */
            using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Students", ConnString))
            {
                SqlCommandBuilder cb = new SqlCommandBuilder(da);
                da.MissingSchemaAction = MissingSchemaAction.AddWithKey;
                da.RowUpdated += OnRowUpdated;
                da.Update(ds.Students);
            }
        }
        private void OnRowUpdated(object sender, SqlRowUpdatedEventArgs e)
        {
            // Include a variable and a command to retrieve the identity value from the Access database.
            SqlCommand idCMD = new SqlCommand("SELECT @@IDENTITY", e.Command.Connection);
            if (e.StatementType != StatementType.Insert) return;
            // Retrieve the identity value and store it in the ID column.
            object newID = idCMD.ExecuteScalar();
            // ID column
            DataColumn primCol = e.Row.Table.PrimaryKey[0];
            e.Row[primCol] = Convert.ChangeType(newID, primCol.DataType);
        }
        internal void CancelAll() => ds.RejectChanges();
        public IEnumerable<DataRow> LoadCountries() => ds.Countries.AsEnumerable();
        public IEnumerable<DataRow> LoadProvinces() => ds.Provinces.AsEnumerable();
        public IEnumerable<DataRow> LoadDistricts() => ds.Districts.AsEnumerable();
        public IEnumerable<DataRow> LoadModerators() => ds.Moderators.AsEnumerable();
        public IEnumerable<DataRow> LoadModeratorType() => ds.ModeratorType.AsEnumerable();
        internal List<CDataSet.ProvincesRow> ProvincesByCountry(DataRow item)
        {
            if (item == null) return null;
            var countryName = item?.GetType().GetProperty("CountryName")?.GetValue(item, null);
            if (countryName == null) return null;
            return ds.Provinces.Where((p) => ((CDataSet.ProvincesRow)p).CountryName == countryName.ToString()).ToList();
        }
        internal List<CDataSet.DistrictsRow> DistrictsByProvinceID(DataRow item)
        {
            var provinceID = item?.GetType().GetProperty("ProvinceID")?.GetValue(item, null);
            if (provinceID == null) return null;
            return ds.Districts.Where((p) => ((CDataSet.DistrictsRow)p).ProvinceID == (int)provinceID).ToList().ToList();
        }

        internal List<CDataSet.ModeratorTypeRow> ModeratorByMaterial(DataRow item)
        {
            if (item == null) return null;
            var material = item?.GetType().GetProperty("Material")?.GetValue(item, null);
            if (material == null) return null;
            return ds.ModeratorType.Where((p) => ((CDataSet.ModeratorTypeRow)p).Moderator == material.ToString()).ToList();
        }

        internal List<CDataSet.ModeratorTypeRow> MassByModerator(DataRow item)
        {
            if (item == null) return null;
            var material = item?.GetType().GetProperty("Material")?.GetValue(item, null);
            if (material == null) return null;
            return ds.ModeratorType.Where((p) => ((CDataSet.ModeratorTypeRow)p).Moderator == material.ToString()).ToList();
        }

    }
}

using System;
using System.Collections.Generic;
using System.Data;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Data;

namespace WpfSimple_v2.ViewModels
{
    public partial class ModeratorConverter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (values == null) return null;

            if (values[0] == null || values[0] == DependencyProperty.UnsetValue) return null;
            var type = values[0].ToString();

            if (values[1] == null || values[1] == DependencyProperty.UnsetValue) return null;

            IList<DataRow> l = (IList<DataRow>)values[1];

            //return  ((CDataSet.ModeratorTypeRow)l[1]).Mass;

            var subTypeList = values[1] as CDataSet.ModeratorTypeRow;

            if (subTypeList == null) return null;


            return subTypeList[type];

        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            return null;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Data;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using WpfSimple_v2.Models;

namespace WpfSimple_v2.ViewModels
{
    public partial class MassConverter : IMultiValueConverter
	{
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (values == null) return null;

            if (values[0] == null || values[0] == DependencyProperty.UnsetValue) return null;
            var type = values[0].ToString();

            if (values[1] == null || values[1] == DependencyProperty.UnsetValue) return null;

            IList<DataRow> l = (IList<DataRow>)values[1];

            //return  ((   CDataSet.ModeratorTypeRow)l[1]).Mass;

            var subTypeList = values[1] as CDataSet.ModeratorTypeRow;

            if (subTypeList == null) return null;


            return subTypeList[type];

        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            return null;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Data;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using WpfSimple_v2.Models;

namespace WpfSimple_v2.ViewModels
{
    public class ConvProvenceID : IMultiValueConverter
    {

		public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
		{
			if (values[0] == DependencyProperty.UnsetValue || values[1] == DependencyProperty.UnsetValue || values[1] == null) return string.Empty;
			int i = (int)values[0];
			IList<DataRow> l = (IList<DataRow>)values[1];
			return i > 0 && (l.Count > 0) ? ((CDataSet.ProvincesRow)l[i - 1]).ProvinceName : string.Empty;
		}
		public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
		{
			throw new NotImplementedException();
		}
	}
}

using System;
using System.Collections.Generic;
using System.Data;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using WpfSimple_v2.Models;

namespace WpfSimple_v2.ViewModels
{
    public class ConvDistrictID : IMultiValueConverter
    {

		public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
		{
			if (values[0] == DependencyProperty.UnsetValue || values[1] == DependencyProperty.UnsetValue || values[1] == null) return string.Empty;
			int i = (int)values[0];
			IList<DataRow> l = (IList<DataRow>)values[1];
			return (i > 0 && l.Count > 0) ? ((CDataSet.DistrictsRow)l[i - 1]).DistrictName : string.Empty;
		}
		public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
		{
			throw new NotImplementedException();
		}
	}

}

using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows.Data;
using System.Windows.Input;

namespace WpfSimple_v2.ViewModels
{
    public class ViewModelMain : INotifyPropertyChanged
    {
        public ViewModelMain()
        {
            DAL da = new DAL();
            da.LoadData();
            //cvsTeachers.Source = da.GetTeachers();
            cvsStudents.Source = da.GetStudents();
            cvsModerators.Source = da.GetModerators();
            //OnPropertyChanged(nameof(AllTeachers));
            OnPropertyChanged(nameof(AllStudents));
            OnPropertyChanged(nameof(AllModerators));
        }
        private CollectionViewSource cvsTeachers = new CollectionViewSource();
        public ICollectionView AllTeachers { get => cvsTeachers.View; }
        private CollectionViewSource cvsStudents = new CollectionViewSource();
        public ICollectionView AllStudents { get => cvsStudents.View; }

        private CollectionViewSource cvsModerators = new CollectionViewSource();
        public ICollectionView AllModerators { get => cvsModerators.View; }
        public ICommand Cmd { get => new RelayCommand(CmdExec); }
        private void CmdExec(object obj)
        {
            switch (obj.ToString())
            {
                case "AddModerator":
                	(new DAL()).AddModerators();
                	break;
                case "AddStudent":
                    (new DAL()).AddStudent();
                    break;
                case "SaveAll":
                    (new DAL()).SaveAll();
                    break;
                case "CancelAll":
                    (new DAL()).CancelAll();
                    OnPropertyChanged(nameof(AllTeachers));
                    OnPropertyChanged(nameof(AllStudents));
                    OnPropertyChanged(nameof(AllModerators));
                    break;
                default:
                    break;
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged([CallerMemberName] string propName = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
    }
}

using System.Collections.ObjectModel;
using System.Data;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

namespace WpfSimple_v2.ViewModels
{
    public partial class PlacesDataGridViewModel
    {
        public PlacesDataGridViewModel() { LoadData(); }
        private void LoadData()
        {
            DAL da = new DAL();
            this.Countries = new ObservableCollection<DataRow>(da.LoadCountries());
            this.Provinces = new ObservableCollection<DataRow>(da.LoadProvinces());
            this.Districts = new ObservableCollection<DataRow>(da.LoadDistricts());
            this.Moderators = new ObservableCollection<DataRow>(da.LoadModerators());
            this.ModeratorType = new ObservableCollection<DataRow>(da.LoadModeratorType());
        }

        public ObservableCollection<DataRow> Countries { get; set; }
        public ObservableCollection<DataRow> Provinces { get; set; }
        public ObservableCollection<DataRow> Districts { get; set; }
        public ObservableCollection<DataRow> Moderators { get; set; }
        public ObservableCollection<DataRow> ModeratorType { get; set; }

        public object CurrentProvinces => (new DAL()).ProvincesByCountry(SelectedItem?.Row);
        public object CurrentDistricts => (new DAL()).DistrictsByProvinceID(SelectedItem?.Row);
        public object CurrentModerator => (new DAL()).ModeratorByMaterial(SelectedItem?.Row);
        public object CurrentMass=> (new DAL()).MassByModerator(SelectedItem?.Row);
        public DataRowView SelectedItem { get; set; }
        public ICommand CmdDelete { get => new RelayCommand(CmdDeleteExec); }
        private void CmdDeleteExec(object obj) => (obj as DataRowView).Delete();
        public static readonly DependencyProperty AttPropProperty = DependencyProperty.Register("AttProp",
            typeof(bool), typeof(DataGrid), new UIPropertyMetadata(false, OnAttProp));
        public static bool GetAttProp(DependencyObject obj) => (bool)obj.GetValue(AttPropProperty);
        public static void SetAttProp(DependencyObject obj, bool value) => obj.SetValue(AttPropProperty, value);
        private static void OnAttProp(DependencyObject depObj, DependencyPropertyChangedEventArgs e)
        {
            var dg = depObj as DataGrid; if (dg == null) return;
            if ((e.NewValue is bool) && (bool)(e.NewValue)) dg.Loaded += Dg_Loaded;
        }
        private static void Dg_Loaded(object sender, RoutedEventArgs e)
        {
            DataGrid dg = sender as DataGrid;
            if (dg == null) return;
            PlacesDataGridViewModel vm = dg.DataContext as PlacesDataGridViewModel;
            if (vm == null) return;
            vm.dg = dg;
        }
        DataGrid dg;
        public static T GetChildOfType<T>(DependencyObject depObj) where T : DependencyObject
        {
            if (depObj == null) return null;
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
            {
                var child = VisualTreeHelper.GetChild(depObj, i);
                var result = (child as T) ?? GetChildOfType<T>(child);
                if (result != null) return result;
            }
            return null;
        }
    }

}

<UserControl x:Class="WpfSimple_v2.UserControl2"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WpfSimple_v2.ViewModels"
             xmlns:vm="clr-namespace:WpfSimple_v2"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
    <UserControl.Resources>
        <local:PlacesDataGridViewModel x:Key="viewModel"/>
        <local:ConvProvenceID x:Key="ConvProvenceID"/>
        <local:ConvDistrictID x:Key="ConvDistrictID"/>
        <local:MassConverter x:Key="MassConverter"/>
        <Color x:Key="GlyphColor">#FF444444</Color>
    </UserControl.Resources>
    <Grid x:Name="grid" DataContext="{StaticResource viewModel}">
        <DataGrid x:Name="moderatordg"
              AutoGenerateColumns="False"
              CanUserAddRows="False"
              ItemsSource="{Binding DataGridItemsSource2, RelativeSource={RelativeSource AncestorType=UserControl}}"
              SelectedItem="{Binding SelectedItem}"
                  DisplayMemberPath="Material"               
              local:PlacesDataGridViewModel.AttProp="True" Margin="0,226,21,52">
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding Material}" Header="Moderator"/>
                <DataGridTemplateColumn Header="Material" Width="120">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <ComboBox IsReadOnly="False"
                                ItemsSource="{Binding ModeratorType, Source={StaticResource viewModel}}"
                                DisplayMemberPath="Moderator"    
                                SelectedValue ="{Binding Material, UpdateSourceTrigger=PropertyChanged}"
                                SelectedValuePath="Moderator"
                                      SelectedItem="{Binding Material}">
                            </ComboBox>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn Header="Mass" Width="130"> 
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition />
                                    <ColumnDefinition Width="20" />
                                </Grid.ColumnDefinitions>
                                <TextBlock>
                                    <TextBlock.Text>
                                        <MultiBinding Converter="{StaticResource MassConverter}">
                                            <Binding Path="Mass"/>
                                            <Binding Path="ModeratorType" Source="{StaticResource viewModel}"/>
                                        </MultiBinding>
                                    </TextBlock.Text>
                                </TextBlock>
                                <Grid Grid.Column="1" MouseDown="Path_MouseDown">
                                    <Path HorizontalAlignment="Center"
                        VerticalAlignment="Center"
                        Data="M 0 0 L 4 4 L 8 0 Z" >
                                        <Path.Fill>
                                            <SolidColorBrush Color="{DynamicResource GlyphColor}"/>
                                        </Path.Fill>
                                    </Path>
                                </Grid>
                            </Grid>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                    <DataGridTemplateColumn.CellEditingTemplate>
                        <DataTemplate DataType="ComboBox">
                            <ComboBox
                                DisplayMemberPath="Mass"
                                ItemsSource="{Binding CurrentMass, Source={StaticResource viewModel}}"
                                SelectedValue="{Binding Mass, UpdateSourceTrigger=PropertyChanged}"
                                SelectedValuePath="Mass" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellEditingTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn Header="Operation">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="Delete Record" Margin="2"
                      Command="{Binding CmdDelete, Source={StaticResource viewModel}}" 
                      CommandParameter="{Binding}" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</UserControl>

Yvon 50

using System;
using System.Collections.Generic;
using System.Data;
using System.Reflection;
using System.Windows;
using System.Windows.Media;

namespace WpfSimple_v2
{
    public static class MyExtensions
    {
        public static T GetParentOfType<T>(this DependencyObject element) where T : DependencyObject
        {
            Type type = typeof(T);
            if (element == null) return null;
            DependencyObject parent = VisualTreeHelper.GetParent(element);
            if (parent == null && ((FrameworkElement)element).Parent is DependencyObject) parent = ((FrameworkElement)element).Parent;
            if (parent == null) return null;
            else if (parent.GetType() == type || parent.GetType().IsSubclassOf(type)) return parent as T;
            return GetParentOfType<T>(parent);
        }
        public static IEnumerable<T> Query<T>(this IDbConnection con, string sql)
        {
            if (con.State == ConnectionState.Closed) con.Open();
            using (IDbCommand cmd = con.CreateCommand())
            {
                cmd.CommandText = sql;
                IDataReader rdr = cmd.ExecuteReader();
                while (rdr.Read())
                {
                    T obj = (T)Activator.CreateInstance(typeof(T));
                    for (int i = 0; i < rdr.FieldCount; i++)
                    {
                        PropertyInfo prop = obj.GetType().GetProperty(rdr.GetName(i), BindingFlags.Public | BindingFlags.Instance);
                        if (null != prop && prop.CanWrite) prop.SetValue(obj, rdr.GetValue(i), null);
                    }
                    yield return obj;
                }
            }
        }
    }
}

using System;
using System.Windows.Input;

namespace WpfSimple_v2
{
    public class RelayCommand : ICommand
    {
        /*
         private readonly Action<object> execute;
         private readonly Predicate<object> canExecute;

         public RelayCommand(Action<object> execute, Predicate<object> canExecute)
         {
             this.execute = execute ?? throw new ArgumentNullException(nameof(execute));
             this.canExecute = canExecute ?? throw new ArgumentNullException(nameof(canExecute));
         }

         public RelayCommand(Action<object> execute) : this(execute, null) { }

         public event EventHandler CanExecuteChanged
         {
             add { CommandManager.RequerySuggested += value; }
             remove { CommandManager.RequerySuggested -= value; }
         }

         public bool CanExecute(object parameter)
         {
             return canExecute == null || canExecute(parameter);
         }

         public void Execute(object parameter)
         {
             execute(parameter);
         }
         */

        private readonly Predicate<object> _canExecute;
        private readonly Action<object> _action;
        public RelayCommand(Action<object> action) { _action = action; _canExecute = null; }
        public RelayCommand(Action<object> action, Predicate<object> canExecute) { _action = action; _canExecute = canExecute; }
        public void Execute(object o) => _action(o);
        public bool CanExecute(object o) => _canExecute == null ? true : _canExecute(o);
        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

    }
}

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Input;
using System.Windows.Media;

namespace WpfSimple_v2
{
    /// <summary>
    /// Interaction logic for UserControl.xaml
    /// </summary>
    public partial class PlacesDataGrid : UserControl
    {
        public PlacesDataGrid()
        {
            InitializeComponent();
        }
        public static readonly DependencyProperty DataGridItemsSourceProperty =
                DependencyProperty.Register("DataGridItemsSource", typeof(IEnumerable), typeof(PlacesDataGrid), new PropertyMetadata(null));
        public IEnumerable DataGridItemsSource
        {
            get { return (IEnumerable)GetValue(DataGridItemsSourceProperty); }
            set { SetValue(DataGridItemsSourceProperty, value); }
        }
        private void Path_MouseDown(object sender, MouseButtonEventArgs e)
        {
            HitTestResult hitTestResult = VisualTreeHelper.HitTest(dg, e.GetPosition(dg));
            DataGridRow dataGridRow = hitTestResult.VisualHit.GetParentOfType<DataGridRow>();
            if (dataGridRow == null) return;
            int index = dataGridRow.GetIndex();
            var item = dg.Items[index];
            if (dg.SelectedItem != item || dg.SelectedItem == null) dg.SelectedItem = item;
            DataGridCell dgc = hitTestResult.VisualHit.GetParentOfType<DataGridCell>();
            if (dgc == null) return;
            dgc.Focus();
            dg.BeginEdit();
        }
        public T GetParentOfType<T>(DependencyObject element) where T : DependencyObject
        {
            Type type = typeof(T);
            if (element == null) return null;
            DependencyObject parent = VisualTreeHelper.GetParent(element);
            if (parent == null && ((FrameworkElement)element).Parent is DependencyObject) parent = ((FrameworkElement)element).Parent;
            if (parent == null) return null;
            else if (parent.GetType() == type || parent.GetType().IsSubclassOf(type)) return parent as T;
            return GetParentOfType<T>(parent);
        }
    }
}

<UserControl x:Class="WpfSimple_v2.PlacesDataGrid"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WpfSimple_v2.ViewModels"
             xmlns:vm="clr-namespace:WpfSimple_v2"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
    <UserControl.Resources>
        <local:PlacesDataGridViewModel x:Key="viewModel"/>
        <local:ConvProvenceID x:Key="ConvProvenceID"/>
        <local:ConvDistrictID x:Key="ConvDistrictID"/>
        <local:MassConverter x:Key="MassConverter"/>
        <Color x:Key="GlyphColor">#FF444444</Color>
    </UserControl.Resources>
    <Grid x:Name="grid" DataContext="{StaticResource viewModel}">
        <DataGrid x:Name="dg"
              AutoGenerateColumns="False"
              CanUserAddRows="False"
              ItemsSource="{Binding DataGridItemsSource, RelativeSource={RelativeSource AncestorType=UserControl}}"
              SelectedItem="{Binding SelectedItem}"
              local:PlacesDataGridViewModel.AttProp="True" Margin="0,0,0,259">
            <DataGrid.Columns>
                <DataGridTemplateColumn Header="Country" Width="120">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <ComboBox
                            ItemsSource="{Binding Countries, Source={StaticResource viewModel}}"
                            DisplayMemberPath="CountryName"
                            SelectedValue="{Binding CountryName, UpdateSourceTrigger=PropertyChanged}"
                            SelectedValuePath="CountryName">
                            </ComboBox>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn Header="Province" Width="130">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition />
                                    <ColumnDefinition Width="20" />
                                </Grid.ColumnDefinitions>
                                <TextBlock>
                                    <TextBlock.Text>
                                        <MultiBinding Converter="{StaticResource ConvProvenceID}">
                                            <Binding Path="ProvinceID"/>
                                            <Binding Path="Provinces" Source="{StaticResource viewModel}"/>
                                        </MultiBinding>
                                    </TextBlock.Text>
                                </TextBlock>
                                <Grid Grid.Column="1" MouseDown="Path_MouseDown">
                                    <Path HorizontalAlignment="Center"
                        VerticalAlignment="Center"
                        Data="M 0 0 L 4 4 L 8 0 Z" >
                                        <Path.Fill>
                                            <SolidColorBrush Color="{DynamicResource GlyphColor}"/>
                                        </Path.Fill>
                                    </Path>
                                </Grid>
                            </Grid>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                    <DataGridTemplateColumn.CellEditingTemplate>
                        <DataTemplate DataType="ComboBox">
                            <ComboBox
                            DisplayMemberPath="ProvinceName"
                            ItemsSource="{Binding CurrentProvinces, Source={StaticResource viewModel}}"
                            SelectedValue="{Binding ProvinceID, UpdateSourceTrigger=PropertyChanged}"
                            SelectedValuePath="ProvinceID" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellEditingTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn Header="District" Width="140">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition />
                                    <ColumnDefinition Width="20" />
                                </Grid.ColumnDefinitions>
                                <TextBlock>
                                    <TextBlock.Text>
                                        <MultiBinding Converter="{StaticResource ConvDistrictID}">
                                            <Binding Path="DistrictID"/>
                                            <Binding Path="Districts" Source="{StaticResource viewModel}"/>
                                        </MultiBinding>
                                    </TextBlock.Text>
                                </TextBlock>
                                <Grid Grid.Column="1" MouseDown="Path_MouseDown" >
                                    <Path Grid.Column="1"
                      HorizontalAlignment="Center"
                      VerticalAlignment="Center"
                      Data="M 0 0 L 4 4 L 8 0 Z" >
                                        <Path.Fill>
                                            <SolidColorBrush Color="{DynamicResource GlyphColor}"/>
                                        </Path.Fill>
                                    </Path>
                                </Grid>
                            </Grid>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                    <DataGridTemplateColumn.CellEditingTemplate>
                        <DataTemplate>
                            <ComboBox
                DisplayMemberPath="DistrictName"
                ItemsSource="{Binding CurrentDistricts, Source={StaticResource viewModel}}"
                SelectedValue="{Binding DistrictID, UpdateSourceTrigger=PropertyChanged}"
                SelectedValuePath="DistrictID" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellEditingTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn Header="Operation">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="Delete Record" Margin="2"
                      Command="{Binding CmdDelete, Source={StaticResource viewModel}}" 
                      CommandParameter="{Binding}" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</UserControl>

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Input;
using System.Windows.Media;

namespace WpfSimple_v2
{
    /// <summary>
    /// Interaction logic for UserControl.xaml
    /// </summary>
    public partial class UserControl2 : UserControl
    {
        public UserControl2()
        {
            InitializeComponent();
        }
        public static readonly DependencyProperty DataGridItemsSource2Property =
                DependencyProperty.Register("DataGridItemsSource2", typeof(IEnumerable), typeof(UserControl2), new PropertyMetadata(null));
        public IEnumerable DataGridItemsSource2
        {
            get { return (IEnumerable)GetValue(DataGridItemsSource2Property); }
            set { SetValue(DataGridItemsSource2Property, value); }
        }
        private void Path_MouseDown(object sender, MouseButtonEventArgs e)
        {
            HitTestResult hitTestResult = VisualTreeHelper.HitTest(moderatordg, e.GetPosition(moderatordg));
            DataGridRow dataGridRow = hitTestResult.VisualHit.GetParentOfType<DataGridRow>();
            if (dataGridRow == null) return;
            int index = dataGridRow.GetIndex();
            var item = moderatordg.Items[index];
            if (moderatordg.SelectedItem != item || moderatordg.SelectedItem == null) moderatordg.SelectedItem = item;
            DataGridCell dgc = hitTestResult.VisualHit.GetParentOfType<DataGridCell>();
            if (dgc == null) return;
            dgc.Focus();
            moderatordg.BeginEdit();
        }
        public T GetParentOfType<T>(DependencyObject element) where T : DependencyObject
        {
            Type type = typeof(T);
            if (element == null) return null;
            DependencyObject parent = VisualTreeHelper.GetParent(element);
            if (parent == null && ((FrameworkElement)element).Parent is DependencyObject) parent = ((FrameworkElement)element).Parent;
            if (parent == null) return null;
            else if (parent.GetType() == type || parent.GetType().IsSubclassOf(type)) return parent as T;
            return GetParentOfType<T>(parent);
        }
    }
}

Peter Fleischer (former MVP) 19,326 Reputation points

2024-04-07T07:07:42.61+00:00

Hi,
please show your data model in detail. Who is master, who is child, what are the foreign keys.
Yvon 50 Reputation points

2024-04-08T16:31:46.8833333+00:00

The moderators is the master table. The moderatorType is just a lookup. There aren't any FK.

Moderators datagrid will use the material column with the drop down returning from the moderatorType.moderator. The Moderators datagrid will use the mass column with the drop down returning from the moderatorType.mass.
Hui Liu-MSFT 48,571 Reputation points Microsoft Vendor

2024-04-09T03:22:32.5966667+00:00

Hi,@Yvon. Welcome to Microsoft Q&A. Could you share your sql code that creates the sql table without private information to clarify the relationship between the tables so we can reproduce the problem? And what is the code for your CSSSDataSet?
Peter Fleischer (former MVP) 19,326 Reputation points

2024-04-09T06:32:33.16+00:00

Hi Yvon,
I think you misunderstand your data model. A lookup points from child table to master table normally via FK. I think you DataGrid shows all moderators and each record (line in DataGrid) points to matarial (master = list of all materials). On otherside you have a table of all mass with information about material. The list of all materials you can get using distinct.

Yvon 50

@Hui Liu-MSFT

create table Moderators(
PartNumber char(20) not null,
Material char(20) null,
Mass char(10) null
) 

create table ModeratorType(
Moderator varchar(20) not null,
Type varchar(1) not null,
Mass char(10) not null
)

Yvon 50

I can't use the Student dataset as guide line then. The moderators data will be passed in with a part number. The datagrid will default the initial dataset values.

I need to the change following when mouse down for the drop down list. The VisualTreeHelper to get the parent is not working here (it's only for Student dataset)

        private void Path_MouseDown(object sender, MouseButtonEventArgs e)
        {
            HitTestResult hitTestResult = VisualTreeHelper.HitTest(moderatordg, e.GetPosition(moderatordg));
            DataGridRow dataGridRow = hitTestResult.VisualHit.GetParentOfType<DataGridRow>();
            if (dataGridRow == null) return;
            int index = dataGridRow.GetIndex();
            var item = moderatordg.Items[index];
            if (moderatordg.SelectedItem != item || moderatordg.SelectedItem == null) moderatordg.SelectedItem = item;
            DataGridCell dgc = hitTestResult.VisualHit.GetParentOfType<DataGridCell>();
            if (dgc == null) return;
            dgc.Focus();
            moderatordg.BeginEdit();
        }
        public T GetParentOfType<T>(DependencyObject element) where T : DependencyObject
        {
            Type type = typeof(T);
            if (element == null) return null;
            DependencyObject parent = VisualTreeHelper.GetParent(element);
            if (parent == null && ((FrameworkElement)element).Parent is DependencyObject) parent = ((FrameworkElement)element).Parent;
            if (parent == null) return null;
            else if (parent.GetType() == type || parent.GetType().IsSubclassOf(type)) return parent as T;
            return GetParentOfType<T>(parent);
        }

3 answers

Peter Fleischer (former MVP) 19,326

Try following demo:

SQL:

USE [CollegeDB]
GO
/****** Object:  Table [dbo].[Moderators] ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Moderators](
	[ID] [int] IDENTITY(1,1) NOT NULL,
	[PartNumber] nvarchar(20) null,
	[Material] nvarchar(20) null,
	[Mass] nvarchar(10) null
 CONSTRAINT [PK_Moderators] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO
/****** Object:  Table [dbo].[ModeratorType] *****/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[ModeratorType](
	[ID] [int] IDENTITY(1,1) NOT NULL,
	[Moderator] nvarchar(20) not null,
	[Type] varchar(1) not null,
	[Mass] nvarchar(10) not null
 CONSTRAINT [PK_ModeratorType] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO
INSERT [dbo].[Moderators] ([PartNumber], [Material], [Mass]) VALUES ('1234','Plastic','<30')
GO
INSERT [dbo].[Moderators] ([PartNumber], [Material], [Mass]) VALUES ('1234','Water','Hot')
GO
INSERT [dbo].[Moderators] ([PartNumber], [Material], [Mass]) VALUES ('1234','Water','Cold')
GO
INSERT [dbo].[Moderators] ([PartNumber], [Material], [Mass]) VALUES ('4567','Metal','Silver')
GO
INSERT [dbo].[ModeratorType] ([Moderator], [Type], [Mass]) VALUES ('Plastic','p','<30')
GO
INSERT [dbo].[ModeratorType] ([Moderator], [Type], [Mass]) VALUES ('Plastic','p','>50')
GO
INSERT [dbo].[ModeratorType] ([Moderator], [Type], [Mass]) VALUES ('Plastic','p','=100')
GO
INSERT [dbo].[ModeratorType] ([Moderator], [Type], [Mass]) VALUES ('Water','w','Hot')
GO
INSERT [dbo].[ModeratorType] ([Moderator], [Type], [Mass]) VALUES ('Water','w','Cold')
GO
INSERT [dbo].[ModeratorType] ([Moderator], [Type], [Mass]) VALUES ('Metal','m','Silver')
GO
INSERT [dbo].[ModeratorType] ([Moderator], [Type], [Mass]) VALUES ('Metal','m','Gold')
GO

MainWindow:

<Window x:Class="WpfApp1.Window004"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp004"
        xmlns:uc="clr-namespace:WpfApp004"
        mc:Ignorable="d"
        Title="Yvon_240406" Height="500" Width="800">
  <Window.Resources>
    <local:ViewModelMain x:Key="vm"/>
  </Window.Resources>
  <Grid DataContext="{StaticResource vm}" Margin="10">
    <Grid.Resources>
      <Style TargetType="Button">
        <Setter Property="Margin" Value="10"/>
        <Setter Property="Width" Value="150"/>
        <Setter Property="Height" Value="25"/>
        <Setter Property="VerticalAlignment" Value="Top"/>
      </Style>
      <Style TargetType="Label">
        <Setter Property="Margin" Value="5"/>
      </Style>
    </Grid.Resources>
    <Grid.RowDefinitions>
      <RowDefinition Height="auto"/>
      <RowDefinition Height="100"/>
      <RowDefinition Height="auto"/>
      <RowDefinition Height="250"/>
      <RowDefinition/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
      <ColumnDefinition/>
      <ColumnDefinition Width="220"/>
    </Grid.ColumnDefinitions>
    <uc:UserControl2 Grid.Row="3" Grid.Column="0" Margin="5"
                     DataGridItemsSource="{Binding AllModerators}"/>
    <Button Grid.Row="3" Grid.Column="1"  Margin="5" Width="150" HorizontalAlignment="Left"
            Content="AddModerator"
            Command="{Binding Cmd}" CommandParameter="AddModerator"/>
    <StackPanel Grid.Row="4" Grid.ColumnSpan="2" HorizontalAlignment="Right" Orientation="Horizontal" >
      <Button Content="CancelAll" Command="{Binding Cmd}" CommandParameter="CancelAll"/>
      <Button Content="SaveAll" Command="{Binding Cmd}" CommandParameter="SaveAll"/>
    </StackPanel>
  </Grid>
</Window>

XAML UserControl:

<UserControl x:Name="userControl"
             x:Class="WpfApp004.UserControl2"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WpfApp004"
             xmlns:vm="clr-namespace:WpfApp004"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
  <UserControl.Resources>
    <vm:ModeratorsDataGridViewModel x:Key="viewModel"/>
    <Color x:Key="GlyphColor">#FF444444</Color>
  </UserControl.Resources>
  <Grid x:Name="grid" DataContext="{StaticResource viewModel}">
    <DataGrid x:Name="dg"
              AutoGenerateColumns="False"
              CanUserAddRows="False"
              ItemsSource="{Binding DataGridItemsSource, RelativeSource={RelativeSource AncestorType=UserControl}}"
              SelectedItem="{Binding SelectedItem}">
      <!--local:ModeratorsDataGridViewModel.AttProp="True">-->
      <DataGrid.Columns>
        <DataGridTextColumn Header="Place" Width="120" Binding="{Binding PartNumber}" />
        <DataGridComboBoxColumn Header="Material" Width="130" 
                                SelectedItemBinding="{Binding Material}"
                                ItemsSource="{Binding AllMaterials, Source={StaticResource viewModel}}"/>
        <DataGridTemplateColumn Header="Mass" Width="140">
          <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
              <Grid>
                <Grid.ColumnDefinitions>
                  <ColumnDefinition />
                  <ColumnDefinition Width="20" />
                </Grid.ColumnDefinitions>
                <TextBlock Text="{Binding Mass}"/>
                <Grid Grid.Column="1" MouseDown="Path_MouseDown">
                  <Path Grid.Column="1"
                      HorizontalAlignment="Center"
                      VerticalAlignment="Center"
                      Data="M 0 0 L 4 4 L 8 0 Z" >
                    <Path.Fill>
                      <SolidColorBrush Color="{DynamicResource GlyphColor}"/>
                    </Path.Fill>
                  </Path>
                </Grid>
              </Grid>
            </DataTemplate>
          </DataGridTemplateColumn.CellTemplate>
          <DataGridTemplateColumn.CellEditingTemplate>
            <DataTemplate>
              <ComboBox
                ItemsSource="{Binding CurrentMaterial, Source={StaticResource viewModel}}"
                SelectedValue="{Binding Mass, UpdateSourceTrigger=PropertyChanged}"/>
            </DataTemplate>
          </DataGridTemplateColumn.CellEditingTemplate>
        </DataGridTemplateColumn>
        <DataGridTemplateColumn Header="Operation">
          <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
              <Button Content="Delete Record" Margin="2"
                      Command="{Binding CmdDelete, Source={StaticResource viewModel}}" 
                      CommandParameter="{Binding}" />
            </DataTemplate>
          </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
      </DataGrid.Columns>
    </DataGrid>
  </Grid>
</UserControl>

CodeBehind UserControl:

using System;
using System.Collections;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
namespace WpfApp004
{
	/// <summary>
	/// Interaction logic for UserControl2.xaml
	/// </summary>
	public partial class UserControl2 : UserControl
	{
		public UserControl2()
		{
			InitializeComponent();
		}
		public static readonly DependencyProperty DataGridItemsSourceProperty =
				DependencyProperty.Register("DataGridItemsSource", typeof(IEnumerable), typeof(UserControl2), new PropertyMetadata(null));
		public IEnumerable DataGridItemsSource
		{
			get { return (IEnumerable)GetValue(DataGridItemsSourceProperty); }
			set { SetValue(DataGridItemsSourceProperty, value); }
		}
		private void Path_MouseDown(object sender, MouseButtonEventArgs e)
		{
			HitTestResult hitTestResult = VisualTreeHelper.HitTest(dg, e.GetPosition(dg));
			DataGridRow dataGridRow = hitTestResult.VisualHit.GetParentOfType<DataGridRow>();
			if (dataGridRow == null) return;
			int index = dataGridRow.GetIndex();
			var item = dg.Items[index];
			if (dg.SelectedItem != item || dg.SelectedItem == null) dg.SelectedItem = item;
			DataGridCell dgc = hitTestResult.VisualHit.GetParentOfType<DataGridCell>();
			if (dgc == null) return;
			dgc.Focus();
			dg.BeginEdit();
		}
		public T GetParentOfType<T>(DependencyObject element) where T : DependencyObject
		{
			Type type = typeof(T);
			if (element == null) return null;
			DependencyObject parent = VisualTreeHelper.GetParent(element);
			if (parent == null && ((FrameworkElement)element).Parent is DependencyObject) parent = ((FrameworkElement)element).Parent;
			if (parent == null) return null;
			else if (parent.GetType() == type || parent.GetType().IsSubclassOf(type)) return parent as T;
			return GetParentOfType<T>(parent);
		}
	}
}

Other Code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Windows;
using System.Windows.Data;
using System.Windows.Input;
using System.Windows.Media;
using WpfApp1;
namespace WpfApp004
{
	public class ViewModelMain : INotifyPropertyChanged
	{
		public ViewModelMain()
		{
			DAL da = new DAL();
			da.LoadData();
			cvsModerators.Source = da.GetModerators();
		}
		private CollectionViewSource cvsModerators = new CollectionViewSource();
		public ICollectionView AllModerators { get => cvsModerators.View; }
		public ICommand Cmd { get => new RelayCommand(CmdExec); }
		private void CmdExec(object obj)
		{
			switch (obj.ToString())
			{
				case "AddModerator":
					(new DAL()).AddModerator();
					break;
				case "SaveAll":
					(new DAL()).SaveAll();
					break;
				case "CancelAll":
					(new DAL()).CancelAll();
					OnPropertyChanged(nameof(AllModerators));
					break;
				default:
					break;
			}
		}
		public event PropertyChangedEventHandler PropertyChanged;
		private void OnPropertyChanged([CallerMemberName] string propName = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
	}
	public partial class ModeratorsDataGridViewModel
	{
		public List<String> AllMaterials { get => new DAL().GetMaterials(); }
		public DataRowView SelectedItem { get; set; }
		public List<String> CurrentMaterial { get => new DAL().GetMassForMaterial(SelectedItem); }
		public ICommand CmdDelete { get => new RelayCommand(CmdDeleteExec); }
		private void CmdDeleteExec(object obj) => (obj as DataRowView).Delete();
		public static T GetChildOfType<T>(DependencyObject depObj) where T : DependencyObject
		{
			if (depObj == null) return null;
			for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
			{
				var child = VisualTreeHelper.GetChild(depObj, i);
				var result = (child as T) ?? GetChildOfType<T>(child);
				if (result != null) return result;
			}
			return null;
		}
	}
	public class DAL
	{
		private string ConnString = WpfApp1.Properties.Settings.Default.cnSQL_CollegDB;
		private static Window004DS ds;
		public void LoadData()
		{
			ds = new Window004DS();
			using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Moderators", ConnString)) da.Fill(ds.Moderators);
			using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM ModeratorType", ConnString)) da.Fill(ds.ModeratorType);
		}
		internal IEnumerable<DataRow> GetModerators() => ds.Moderators;
		internal List<string> GetMaterials() => new List<string>(ds.ModeratorType.AsEnumerable().Select(row => row.Moderator).Distinct());
		internal List<string> GetMassForMaterial(DataRowView item)
		{
			if (item == null) return new List<string>();
			string mat = ((Window004DS.ModeratorsRow)item.Row).Material;
			return new List<string>(ds.ModeratorType.AsEnumerable().Where(row => row.Moderator == mat).Select(row => row.Mass).Distinct());
		}
		internal void AddModerator() => ds.Moderators.Rows.Add(ds.Moderators.NewRow());
		internal void SaveAll()
		{
			using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Moderators", ConnString))
			{
				SqlCommandBuilder cb = new SqlCommandBuilder(da);
				da.MissingSchemaAction = MissingSchemaAction.AddWithKey;
				da.RowUpdated += OnRowUpdated;
				da.Update(ds.Moderators);
			}
		}
		private void OnRowUpdated(object sender, SqlRowUpdatedEventArgs e)
		{
			// Include a variable and a command to retrieve the identity value from the Access database.
			SqlCommand idCMD = new SqlCommand("SELECT @@IDENTITY", e.Command.Connection);
			if (e.StatementType != StatementType.Insert) return;
			// Retrieve the identity value and store it in the ID column.
			object newID = idCMD.ExecuteScalar();
			// ID column
			DataColumn primCol = e.Row.Table.PrimaryKey[0];
			e.Row[primCol] = Convert.ChangeType(newID, primCol.DataType);
		}
		internal void CancelAll() => ds.RejectChanges();
	}
	public class RelayCommand : ICommand
	{
		private readonly Predicate<object> _canExecute;
		private readonly Action<object> _action;
		public RelayCommand(Action<object> action) { _action = action; _canExecute = null; }
		public RelayCommand(Action<object> action, Predicate<object> canExecute) { _action = action; _canExecute = canExecute; }
		public void Execute(object o) => _action(o);
		public bool CanExecute(object o) => _canExecute == null ? true : _canExecute(o);
		public event EventHandler CanExecuteChanged
		{
			add { CommandManager.RequerySuggested += value; }
			remove { CommandManager.RequerySuggested -= value; }
		}
	}
}
namespace WpfApp004
{
	public static class MyExtensions
	{
		public static T GetParentOfType<T>(this DependencyObject element) where T : DependencyObject
		{
			Type type = typeof(T);
			if (element == null) return null;
			DependencyObject parent = VisualTreeHelper.GetParent(element);
			if (parent == null && ((FrameworkElement)element).Parent is DependencyObject) parent = ((FrameworkElement)element).Parent;
			if (parent == null) return null;
			else if (parent.GetType() == type || parent.GetType().IsSubclassOf(type)) return parent as T;
			return GetParentOfType<T>(parent);
		}
	}
}

Result:

Yvon 50 Reputation points

2024-04-12T17:52:57.69+00:00

@Peter Fleischer (former MVP)

I can't change the schema on the "Moderators and ModeratorTYpe". They are very old schema. I can't use ID as primary key.

They are overloading tables. Therefore, the code you have I still can't display the initial value on the material columns.
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Yvon 50 Reputation points

2024-04-12T17:55:04.4633333+00:00

the schema can't be changed:

create table Moderators( PartNumber char(20) not null, Material char(20) null, Mass char(10) null ) create table ModeratorType( Moderator varchar(20) not null, Type varchar(1) not null, Mass char(10) not null )

Yvon 50 Reputation points

2024-04-12T22:31:24.7066667+00:00

The Add and SaveAll also will not work without ID column
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Yvon 50 Reputation points

2024-04-12T23:25:28.7266667+00:00

Need to turn on this property. The initial values show

The Add/Delete and SaveAll are not working.

The Add with the drop down on mass return empty. Delete has removed a record, but when 'SaveAll', nothing happened
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Peter Fleischer (former MVP) 19,326 Reputation points

2024-04-13T07:02:21.7566667+00:00

Hi,
using DataSet/DataAdapter/CommandBuilder/Update you must have primary key to identify records. Only Fill and Insert (Add) methods works without primary key. If you must use data without primary key you must write your own methods to update/delete records.
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MVVM datagrid comboboxes are not displaying the initial values and the moderator dropdown list needs to be unique

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