Create, define, or generate a KeyDown / PreviewKeyDown event for DataGridTextColumn or DataGridCell in WPF

Question

Hi
My project includes DataGrid, and I'd like to be able to control the type of user input.

I defined a PreviewKeyDown event for DataGridTextColumn, but it does not work and gives me an error.

<DataGridTextColumn x:Name="DateOfBirth" Binding="{Binding DateOfBirth}" Keyboard.PreviewKeyDown="DateOfBirth_PreviewKeyDown" Width="SizeToHeader"/>  

Error: DateOfBirth_PreviewKeyDown is not valid. PreviewKeyDown is not an event on System.Windows.Controls.DataGridTextColumn. Line 1462 Position 155.
I tried other options as well, but I couldn't come to a conclusion.
In WPF, how do I define, create, or generate a KeyDown / PreviewKeyDown event for a DataGridTextColumn?

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

Answer 1

If you want to restrict the type of input data for a particular column, you could try to refer to the code below.
MainWindow.xaml:

  <Window.Resources>  
        <CollectionViewSource x:Key="CountryView" Source="{Binding Countries}"/>  
    </Window.Resources>  
    <Grid>  
        <DataGrid x:Name="dg" Width="200" Height="250" ItemsSource="{Binding Source={StaticResource CountryView}}"   
                  SelectedItem="{Binding SelectedCountry}"  AutoGenerateColumns="False">  
            <DataGrid.Columns>  
                <DataGridTextColumn Header="name" Binding="{Binding Country}"/>  
                <DataGridTemplateColumn Header="daten">  
                    <DataGridTemplateColumn.CellTemplate>  
                        <DataTemplate>  
                            <TextBlock Text="{Binding Daten}"/>  
                        </DataTemplate>  
                    </DataGridTemplateColumn.CellTemplate>  
                    <DataGridTemplateColumn.CellEditingTemplate>  
                        <DataTemplate>  
                            <TextBox Text="{Binding  Daten}" PreviewKeyDown="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.Input;  

namespace DataGridBindICollectionView  
{  
  public partial class MainWindow : Window  
  {  
   ViewModel vm = new ViewModel();  
    public MainWindow()  
    {  
      InitializeComponent();  
      DataContext = vm;  
    }  
    private void TextBox_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)  
    {  
      if (e.Key != Key.D0 && e.Key != Key.D1 && e.Key != Key.D2 && e.Key != Key.D3 && e.Key != Key.D4 && e.Key != Key.D5 && e.Key != Key.D6 && e.Key != Key.D7 && e.Key != Key.D8 && e.Key != Key.D9 && e.Key != Key.Back && e.Key != Key.NumPad0 && e.Key != Key.NumPad1 && e.Key != Key.NumPad2 && e.Key != Key.NumPad3 && e.Key != Key.NumPad4 && e.Key != Key.NumPad5 && e.Key != Key.NumPad6 && e.Key != Key.NumPad7 && e.Key != Key.NumPad8 && e.Key != Key.NumPad9 && e.Key != Key.Delete && e.Key != Key.Right && e.Key != Key.Left)  

      {  

        e.Handled = true;  

      }  
      if (e.Key == Key.Space || e.Key == Key.Back)  
      {  
        e.Handled = true;  
      }  
    }  
  }  
  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", Daten = DateTime.Now });  
      Countries.Add(new MyCountry() { Country = "NewYork", Daten = DateTime.Now });  
      Countries.Add(new MyCountry() { Country = "Shanghai", Daten = DateTime.Now });  
    }  
  }  
  public class MyCountry  
  {  
    public string Country { get; set; }  
    public DateTime Daten { get;set;}  
  }  
}  

The result:
You can only enter numbers, not characters.

---

If the response is helpful, please click "Accept Answer" and upvote it.
 Note: Please follow the steps in our [documentation][5] to enable e-mail notifications if you want to receive the related email notification for this thread. 

[5]: https://learn.microsoft.com/en-us/answers/articles/67444/email-notifications.html

Answer 2

My solution is as follows:
First: In XAML and C#, define the PreviewKeyDown and rename the Handler as follows.

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

Then in the PreviewKeyDown event (C#), you can set a limit.

    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.OemQuestion) || 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:  
                MessageBox.Show("Character " + e.Key.ToString() + " is not allowed", "Information", MessageBoxButton.OK, MessageBoxImage.Information);  
                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;  
                }  
                break;  
        }  
    }  

Output (tested in Visual Studio 2017, .Net Framework 4.5.2):

Thanks