How Do I unselect a WPF datagrid row if already selected?

Question

In my datagrid the DataGridTextColumn are binded to a database columns & I have the following properties and events set

SelectionMode="Single"
SelectionUnit="FullRow"
SelectionChanged="dataGrid1_SelectionChanged"

Where

 void dataGrid1_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
 DataGrid grid = (DataGrid)sender;
 dynamic selected_row = grid.SelectedItem;

 EmpID.Text = selected_row["EmpID"].ToString();
 FullName.Text = selected_row["FullName"].ToString();
 Age.Text = FormattedDate(selected_row["Age"].ToString());
 DOJ.Text = selected_row["DOJ"].ToString();
 }

EmpID, FullName, ... on the left side of the above code are just textboxes.

How do I unselect the selected row when I click it or use Ctrl+Click to unselect whichever is easier/better ?

When I hit the Ctrl+Click on a selected row right now I get the error Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: Cannot perform runtime binding on a null reference

Answer 1

MainWindow.xaml:

<Window.DataContext>  
        <local:ViewModel/>  
    </Window.DataContext>  
    <Grid>  
        <Grid.RowDefinitions>  
            <RowDefinition/>  
            <RowDefinition/>  
        </Grid.RowDefinitions>  
        <DataGrid x:Name="dg" Height="260" Width="290"  ItemsSource="{Binding Items}"  SelectionMode="Single"   
                  AutoGenerateColumns="False"    SelectionUnit="FullRow"  SelectionChanged="dg_SelectionChanged" >  
            <DataGrid.Resources>  
                <Style TargetType="{x:Type DataGridCell}">  
                    <EventSetter Event="PreviewMouseLeftButtonDown" Handler="DoSelectedRow"/>  
                </Style>  
            </DataGrid.Resources>  
            <DataGrid.Columns>  
                <DataGridTextColumn x:Name="ID" Header="ID" Binding="{Binding ID}"/>  
                <DataGridTextColumn x:Name="FullName" Header="FullName" Binding="{Binding FullName}"/>  
                <DataGridTextColumn x:Name="Description" Header="Description" Binding="{Binding Description}"/>  
            </DataGrid.Columns>  
        </DataGrid>  
        <StackPanel Grid.Row="1">  
            <TextBox x:Name="ImID" Width="100" Height="40"/>  
            <TextBox x:Name="ImFullName" Width="100" Height="40"/>  
            <TextBox x:Name="ImDescription" Width="100" Height="40"/>  
        </StackPanel>  
    </Grid>  

MainWindow.xaml.cs:

using System.Collections.ObjectModel;  
using System.ComponentModel;  
using System.Windows;  
using System.Windows.Controls;  
using System.Windows.Input;  
using System.Windows.Media;  
  
namespace DataGridSelected  
{  
  public partial class MainWindow : Window  
  {  
    public MainWindow()  
    {  
      InitializeComponent();  
    }  
    private void dg_SelectionChanged(object sender, SelectionChangedEventArgs e)  
    {  
      DataGrid grid = (DataGrid)sender;  
      dynamic selected_row = grid.SelectedItem;  
      //ImID.Text= selected_row["ID"].ToString();  
    }  
    public void DoSelectedRow(object sender, MouseButtonEventArgs e)  
    {  
      DataGridCell cell = sender as DataGridCell;  
      if (cell != null && !cell.IsEditing)  
      {  
        DataGridRow row = FindVisualParent<DataGridRow>(cell);  
        if (row != null)  
        {  
          row.IsSelected = !row.IsSelected;  
          e.Handled = true;  
        }  
      }  
    }  
    public static Parent FindVisualParent<Parent>(DependencyObject child)   where Parent : DependencyObject  
    {  
      DependencyObject parentObject = child;  
  
      while (!((parentObject is System.Windows.Media.Visual)  
              || (parentObject is System.Windows.Media.Media3D.Visual3D)))  
      {  
        if (parentObject is Parent || parentObject == null)  
        {  
          return parentObject as Parent;  
        }  
        else  
        {  
          parentObject = (parentObject as FrameworkContentElement).Parent;  
        }  
      }  
      parentObject = VisualTreeHelper.GetParent(parentObject);  
      if (parentObject is Parent || parentObject == null)  
      {  
        return parentObject as Parent;  
      }  
      else  
      {  
        return FindVisualParent<Parent>(parentObject);  
      }  
    }  
  }  
  public class ViewModel : INotifyPropertyChanged  
  {  
    private int _selectedIndex = 0;  
    public int SelectedIndex  
    {  
      get { return _selectedIndex; }  
      set { _selectedIndex = value; OnPropertyChanged("SelectedIndex"); }  
    }  
  
    private ObservableCollection<Item> items = new ObservableCollection<Item>();  
    public ObservableCollection<Item> Items  
    {  
      get { return items; }  
      set { items = value; }  
    }  
    public ViewModel()  
    {  
      Items.Add(new Item() { ID="1", FullName="image1",  Description = "image1" });  
      Items.Add(new Item() { ID = "2", FullName = "image2",  Description = "image2" });  
      Items.Add(new Item() { ID = "3", FullName = "image3", Description = "image3" });  
      Items.Add(new Item() { ID = "4", FullName = "image4", Description = "image4" });  
    }  
    public event PropertyChangedEventHandler PropertyChanged;  
    private void OnPropertyChanged(string propertyName)  
    {  
      if (this.PropertyChanged != null)  
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));  
    }  
  }  
  public class Item : INotifyPropertyChanged  
  {  
    private string id;  
    public string ID  
    {  
      get { return id; }  
      set { id = value; OnPropertyChanged("ID"); }  
    }  
    private string fullName;  
    public string FullName  
    {  
      get { return fullName; }  
      set { fullName = value; OnPropertyChanged("FullName"); }  
    }  
    private string description;  
    public string Description  
    {  
      get { return description; }  
      set { description = value; OnPropertyChanged("Description"); }  
    }  
    public event PropertyChangedEventHandler PropertyChanged;  
    private void OnPropertyChanged(string propertyName)  
    {  
      if (this.PropertyChanged != null)  
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));  
    }  
  }  
}  

The result:

Update:

<Grid>  
        <Grid.RowDefinitions>  
            <RowDefinition/>  
            <RowDefinition/>  
        </Grid.RowDefinitions>  
        <DataGrid x:Name="dg" Height="260" Width="290"  SelectionMode="Single"  AutoGenerateColumns="False"   
                    SelectionUnit="FullRow"   SelectionChanged="dg_SelectionChanged" >  
            <DataGrid.Resources>  
                <Style TargetType="{x:Type DataGridCell}">  
                    <EventSetter Event="PreviewMouseLeftButtonDown" Handler="DoSelectedRow"/>  
                </Style>  
            </DataGrid.Resources>  
            <DataGrid.Columns>  
                <DataGridTextColumn x:Name="ID" Header="ID" Binding="{Binding Id}"/>  
                <DataGridTextColumn x:Name="FullName" Header="FullName" Binding="{Binding FullName}"/>  
                <DataGridTextColumn x:Name="Description" Header="Description" Binding="{Binding Description}"/>  
            </DataGrid.Columns>  
        </DataGrid>  
        <TextBox x:Name="ImID" Grid.Row="1"  Width="100" Height="50" />  
    </Grid>  

MainWindow.xaml.cs:

using System.Collections.Generic;  
using System.Data;  
using System.Data.SqlClient;  
using System.Linq;  
using System.Windows;  
using System.Windows.Controls;  
using System.Windows.Input;  
using System.Windows.Media;  
  
namespace DataGridSelected  
{  
  public partial class MainWindow : Window  
  {  
    public MainWindow()  
    {  
      InitializeComponent();  
      FillGrid();  
    }  
    private void FillGrid()  
    {  
      string constr = @"constr";  
  
      SqlConnection con = new SqlConnection(constr);  
      con.Open();  
      SqlCommand cmd = new SqlCommand("Select * From [dbo].[Table]", con);  
      SqlDataAdapter da = new SqlDataAdapter(cmd);  
      var dt = new DataTable();  
      da.Fill(dt);  
      dg.ItemsSource = dt.DefaultView;  
      List<int> SelectedIndexs = dg.SelectedItems  
        .Cast<DataRowView>()  
        .Select(view => dt.Rows.IndexOf(view.Row))  
        .ToList();  
      con.Close();  
    }  
        private void dg_SelectionChanged(object sender, SelectionChangedEventArgs e)  
        {  
           DataGrid grid = (DataGrid)sender;  
           dynamic selected_row = grid.SelectedItem;  
            if (selected_row == null)  
            {  
                ImID.Text = "";  
            }  
            else  
            {  
                ImID.Text = selected_row["ID"].ToString();  
            }  
             
        }  
        public void DoSelectedRow(object sender, MouseButtonEventArgs e)  
    {  
      DataGridCell cell = sender as DataGridCell;  
      if (cell != null && !cell.IsEditing)  
      {  
        DataGridRow row = FindVisualParent<DataGridRow>(cell);  
        if (row != null)  
        {  
          row.IsSelected = !row.IsSelected;  
                 
          e.Handled = true;  
        }  
      }  
    }  
    public static Parent FindVisualParent<Parent>(DependencyObject child)   where Parent : DependencyObject  
    {  
      DependencyObject parentObject = child;  
  
      while (!((parentObject is System.Windows.Media.Visual)  
              || (parentObject is System.Windows.Media.Media3D.Visual3D)))  
      {  
        if (parentObject is Parent || parentObject == null)  
        {  
          return parentObject as Parent;  
        }  
        else  
        {  
          parentObject = (parentObject as FrameworkContentElement).Parent;  
        }  
      }  
      parentObject = VisualTreeHelper.GetParent(parentObject);  
      if (parentObject is Parent || parentObject == null)  
      {  
        return parentObject as Parent;  
      }  
      else  
      {  
        return FindVisualParent<Parent>(parentObject);  
      }  
    }  
  }  
}  

The result:
selected item 4:

unselected item 4:

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