The keyboard inputs are not updating correctly in the hosted WinForms application

Question

Hi,

We are encountering an issue in a WPF application hosted within a WinForms application. The keyboard event is triggered correctly, but the values are not updating properly in the UI.

 

Here’s the setup:

1. Create a WinForms application with a user control.
2. Create a WPF application with two XAML files.
3. In the WinForms user control, add an element host for the WPF control.
4. In the WPF control’s code-behind, create an instance of the main window and display it using button click.
5. The main window has a TextBox, but when attempting to type letters or numbers in key board, the TextBox does not update in the UI.

public partial class ReportHost : UserControl
{
    private ElementHost _elementHost;
    public ReportHost()
    {
        InitializeComponent();
        var wpfControl = new WpfControl();
        _elementHost = new ElementHost()
        {
            Dock = DockStyle.Fill,
        };
        _elementHost.Child = wpfControl;
        Controls.Add(_elementHost);
    }
}

<UserControl
    x:Class="ShowReport.WpfControl"
    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:local="clr-namespace:ShowReport"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    d:DesignHeight="450"
    d:DesignWidth="800"
    mc:Ignorable="d">
    <Grid>
        <Button Click="ButtonBase_OnClick" Content="Show PDF Viewer" />
    </Grid>
</UserControl>

public partial class WpfControl : UserControl
{
    public WpfControl()
    {
        InitializeComponent();
    }
    private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
    {
        var window = new MainWindow();
        window.Show();
    }
}

<Window
    x:Class="ShowReport.MainWindow"
    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:local="clr-namespace:ShowReport"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="MainWindow"
    Width="800"
    Height="450"
    mc:Ignorable="d">
    <TextBox Height="100" Width="200"/>
</Window>

Could you kindly check the code snippet and suggest a solution to resolve this issue?

Answer 1

Hi @Yathavakrishnan , Welcome to Microsoft Q&A,

Call the ElementHost.EnableModelessKeyboardInterop method before showing a new WPF window to enable keyboard interoperation between WinForms and WPF.

using System.Windows.Forms.Integration; 

public partial class WpfControl : UserControl
{
    public WpfControl()
    {
        InitializeComponent();
    }
    private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
    {
        var window = new MainWindow();
        ElementHost.EnableModelessKeyboardInterop(window);
        window.Show();
    }
}

Best Regards,

Jiale

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