How to enter or bind data from another field to the selected DataGridCell in the PreviewKeyDown event?

Question

Hi
I use the following method to set the TextBox date limit.
XAML (MaxLength):

<TextBox x:Name="LoanDate_TextBox" PreviewKeyDown="LoanDate_TextBox_PreviewKeyDown" GotFocus="LoanDate_TextBox_GotFocus" LostFocus="LoanDate_TextBox_LostFocus" Padding="4,4,0,0" Template="{StaticResource TextBoxControlTemplate}" HorizontalAlignment="Left" Height="30" MaxLength="10" TextWrapping="Wrap" VerticalAlignment="Top" Width="178" Margin="0,51,0,0"/>  

C#:

    private void LoanDate_TextBox_PreviewKeyDown(object sender, KeyEventArgs e)  
    {  
        switch (!((e.Key >= Key.D0 && e.Key <= Key.D9) || (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9) || e.Key == Key.Back || e.Key == Key.Home || e.Key == Key.End || e.Key == Key.Left || e.Key == Key.Right || e.Key == Key.Tab || Keyboard.Modifiers == ModifierKeys.Control))  
        {  
            case true:  
                e.Handled = true;  
                break;  
            default:  
                switch (e.Key == Key.A || e.Key == Key.C || e.Key == Key.V || e.Key == Key.Y || e.Key == Key.Z)  
                {  
                    case true:  
                        break;  
                }  
                switch (e.Key != Key.Back && e.Key != Key.Home && e.Key != Key.End && e.Key != Key.Left && e.Key != Key.Right)  
                {  
                    case true:  
                        byte j = 0;  
                        for (byte i = 0; i < LoanDate_TextBox.Text.Length; i++)  
                        {  
                            switch (LoanDate_TextBox.Text[i] == '/')  
                            {  
                                case true:  
                                    j++;  
                                    break;  
                            }  
                        }  
                        switch (j < 2)  
                        {  
                            case true:  
                                switch (LoanDate_TextBox.Text.Length)  
                                {  
                                    case 2:  
                                        LoanDate_TextBox.Text = '/' + LoanDate_TextBox.Text;  
                                        break;  
                                    case 5:  
                                        LoanDate_TextBox.Text = '/' + LoanDate_TextBox.Text;  
                                        break;  
                                }  
                                break;  
                        }  
                        break;  
                    default:  
                        switch (e.Key)  
                        {  
                            case Key.Back:  
                                switch (App.EnumLanguage)  
                                {  
                                    case AllLanguage.Persian:  
                                        switch (LoanDate_TextBox.Text.Length)  
                                        {  
                                            case 3:  
                                                LoanDate_TextBox.SelectionStart = 3;  
                                                break;  
                                            case 6:  
                                                LoanDate_TextBox.SelectionStart = 6;  
                                                break;  
                                        }  
                                        break;  
                                }  
                                break;  
                        }  
                        break;  
                }  
                break;  
        }  
    }  

As you can see it works fine (I just enter numbers):

So I tried to use this method in the DataGridCell PreviewKeyDown event.
XAML:

<DataGridTextColumn x:Name="DateTaken" Binding="{Binding DateTaken}" Width="SizeToHeader">  
  <DataGridTextColumn.CellStyle>  
    <Style TargetType="DataGridCell">  
       <EventSetter Event="PreviewKeyDown" Handler="DateTaken_PreviewKeyDown"/>  
    </Style>  
  </DataGridTextColumn.CellStyle>  
</DataGridTextColumn>  

C#:

    TextBox DataGridTextColumnValue = new TextBox();  
    public string InputTextFilter(string Input)  
    {  
        StringBuilder FilteredString = new StringBuilder();  
        for (byte i = 0; i < Input.Length; i++)  
        {  
            switch (char.IsDigit(Input[i]) || Input[i] == '/')  
            {  
                case true:  
                    FilteredString.Append(Input[i]);  
                    break;  
            }  
        }  
        return FilteredString.ToString();  
    }  
    private void DateTaken_PreviewKeyDown(object sender, KeyEventArgs e)  
    {  
        switch (!((e.Key >= Key.D0 && e.Key <= Key.D9) || (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9) || e.Key == Key.Back || e.Key == Key.Home || e.Key == Key.End || e.Key == Key.Left || e.Key == Key.Right || e.Key == Key.Tab || Keyboard.Modifiers == ModifierKeys.Control))  
        {  
            case true:  
                e.Handled = true;  
                break;  
            default:  
                DataRowView DV = (DataRowView)BookDataGrid.SelectedItem;  
                DataGridTextColumnValue.Text = InputTextFilter(BookDataGrid.CurrentCell.Column.GetCellContent(DV).ToString());  
                switch (e.Key == Key.A || e.Key == Key.C || e.Key == Key.V || e.Key == Key.Y || e.Key == Key.Z)  
                {  
                    case true:  
                        break;  
                }  
                switch (e.Key != Key.Back && e.Key != Key.Home && e.Key != Key.End && e.Key != Key.Left && e.Key != Key.Right)  
                {  
                    case true:  
                        byte j = 0;  
                        for (byte i = 0; i < DataGridTextColumnValue.Text.Length; i++)  
                        {  
                            switch (DataGridTextColumnValue.Text[i] == '/')  
                            {  
                                case true:  
                                    j++;  
                                    break;  
                            }  
                        }  
                        switch (j < 2)  
                        {  
                            case true:  
                                switch (DataGridTextColumnValue.Text.Length)  
                                {  
                                    case 2:  
                                        DataGridTextColumnValue.Text = '/' + DataGridTextColumnValue.Text;  
                                        break;  
                                    case 5:  
                                        DataGridTextColumnValue.Text = '/' + DataGridTextColumnValue.Text;  
                                        break;  
                                }  
                                break;  
                        }  
                        break;  
                    default:  
                        switch (e.Key)  
                        {  
                            case Key.Back:  
                                switch (App.EnumLanguage)  
                                {  
                                    case AllLanguage.Persian:  
                                        switch (DataGridTextColumnValue.Text.Length)  
                                        {  
                                            case 3:  
                                                DataGridTextColumnValue.SelectionStart = 3;  
                                                break;  
                                            case 6:  
                                                DataGridTextColumnValue.SelectionStart = 6;  
                                                break;  
                                        }  
                                        break;  
                                }  
                                break;  
                        }  
                        break;  
                }  
                break;  
        }  
    }  

Now my question is how to bind the DataGridTextColumnValue text to the selected DataGridCell (lines 50 and 53) ?

Thanks for your attention. I’m looking forward to your reply.

Answer 1

I tried DateTaken_PreviewKeyDown and LoanDate_TextBox_PreviewKeyDown in the EventSetter of CellStyle , without success. You could try by binding the TextBox with the PreviewKeyDown event to the DataGridTemplateCloumn. I commented the relevant code for App.EnumLanguage because I don't know its definition.
MainWindow.xaml:

 <Window.Resources>  
        <CollectionViewSource x:Key="CountryView" Source="{Binding Countries}"/>  
    </Window.Resources>  
    <Grid>  
        <DataGrid x:Name="BookDataGrid" Width="400" Height="250" ItemsSource="{Binding Source={StaticResource CountryView}}"   
                   SelectedItem="{Binding SelectedCountry}"  AutoGenerateColumns="False">  
            <DataGrid.Columns>  
                <DataGridTextColumn Header="name" Binding="{Binding Country}"/>  

                <DataGridTemplateColumn Header="daten"  Width="100" >  

                    <DataGridTemplateColumn.CellTemplate>  
                        <DataTemplate>  
                            <TextBlock Text="{Binding DateTaken}"/>  
                        </DataTemplate>  
                    </DataGridTemplateColumn.CellTemplate>  
                    <DataGridTemplateColumn.CellEditingTemplate >  
                        <DataTemplate>  
                            <TextBox x:Name="DataGridTextColumnValue" Text="{Binding  DateTaken}" PreviewKeyDown="LoanDate_TextBox_PreviewKeyDown"/>  

                        </DataTemplate>  
                    </DataGridTemplateColumn.CellEditingTemplate>  
                </DataGridTemplateColumn>  
            </DataGrid.Columns>  

        </DataGrid>  
    </Grid>  

MainWindow.xaml.cs:

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

namespace PreviewKeyDownDataGridCell  
{  
  public partial class MainWindow : Window  
  {  
    ViewModel vm = new ViewModel();  
    public MainWindow()  
    {  
      InitializeComponent();  
      DataContext = vm;  
    }  

        private void LoanDate_TextBox_PreviewKeyDown(object sender, KeyEventArgs e)  
        {  

            var LoanDate_TextBox  = sender as TextBox;  
            switch (!((e.Key >= Key.D0 && e.Key <= Key.D9) || (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9) || e.Key == Key.Back || e.Key == Key.Home || e.Key == Key.End || e.Key == Key.Left || e.Key == Key.Right || e.Key == Key.Tab || Keyboard.Modifiers == ModifierKeys.Control))  
            {  
                case true:  
                    e.Handled = true;  
                    break;  
                default:  
                    switch (e.Key == Key.A || e.Key == Key.C || e.Key == Key.V || e.Key == Key.Y || e.Key == Key.Z)  
                    {  
                        case true:  
                            break;  
                    }  
                    switch (e.Key != Key.Back && e.Key != Key.Home && e.Key != Key.End && e.Key != Key.Left && e.Key != Key.Right)  
                    {  
                        case true:  
                            byte j = 0;  
                            for (byte i = 0; i < LoanDate_TextBox.Text.Length; i++)  
                            {  
                                switch (LoanDate_TextBox.Text[i] == '/')  
                                {  
                                    case true:  
                                        j++;  
                                        break;  
                                }  
                            }  
                            switch (j < 2)  
                            {  
                                case true:  
                                    switch (LoanDate_TextBox.Text.Length)  
                                    {  
                                        case 2:  
                                            LoanDate_TextBox.Text = '/' + LoanDate_TextBox.Text;  
                                            break;  
                                        case 5:  
                                            LoanDate_TextBox.Text = '/' + LoanDate_TextBox.Text;  
                                            break;  
                                    }  
                                    break;  
                            }  
                            break;  
                        default:  
                            //switch (e.Key)  
                            //{  
                            //    case Key.Back:  
                            //        switch (App.EnumLanguage)  
                            //        {  
                            //            case AllLanguage.Persian:  
                            //                switch (LoanDate_TextBox.Text.Length)  
                            //                {  
                            //                    case 3:  
                            //                        LoanDate_TextBox.SelectionStart = 3;  
                            //                        break;  
                            //                    case 6:  
                            //                        LoanDate_TextBox.SelectionStart = 6;  
                            //                        break;  
                            //                }  
                            //                break;  
                            //        }  
                            //        break;  
                            //}  
                            break;  
                    }  
                    break;  
            }  
        }  
  }  
  public class ViewModel  
  {  
    public ObservableCollection<MyCountry> Countries { get; set; }  
    public MyCountry SelectedCountry { get; set; }  
    public ViewModel()  
    {  
      Countries = new ObservableCollection<MyCountry>();  
      Countries.Add(new MyCountry() { Country = "Beijing", DateTaken = DateTime.Now });  
      Countries.Add(new MyCountry() { Country = "NewYork", DateTaken = DateTime.Now });  
      Countries.Add(new MyCountry() { Country = "Shanghai", DateTaken = DateTime.Now });  
    }  
  }  
  public class MyCountry  
  {  
    public string Country { get; set; }  
    public DateTime DateTaken { get; set; }  
  }  
}  

The result:

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