How do I simulate Text input to a WPF TextBox?

Question

I want to simulate user input to a WPF TextBox. I want to input a character such that the OnPreviewTextInput event is triggered. I tried setting the Text through the Text property, but this didn't trigger the event:

public void SomeFunction()
{
    var textBox = new TextBox();
    textBox.Text = "A";                     
}

Can I trigger the event explicitly somehow?

score 22 · Accepted Answer · edited May 23 '17 at 10:30

22

See the answer to How can I programmatically generate keypress events in C#? for a good description of how to simulate input events.

You could also do:

TextCompositionManager.StartComposition(
    new TextComposition(InputManager.Current, textBox, "A"));

This will raise the PreviewTextInput event and then raise the TextInput event and change the text.

edited May 23 '17 at 10:30

Community

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answered Aug 04 '10 at 12:22

Quartermeister

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What about backspace? – Jordan Dec 02 '13 at 15:31
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@Jordan: You should just ask that as a new question. You might be looking for something like `EditingCommands.Backspace.Execute(null, textBox);`, but it's hard to say without more detail. – Quartermeister Dec 02 '13 at 16:15
Very helpful. Thank you. – treaschf Jun 11 '16 at 17:22

score 4 · Answer 2 · answered Aug 04 '10 at 12:37

4

Another way to do this would be by using WinAPI, SendMessage to be specific:

[DllImport("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);

Then call it this way, when the focus is on the TextBox:

SendMessage(new WindowInteropHelper(this).Handle, 0x0102, 72, 0)

0x0102 is the constant value for WM_CHAR and 72 is the keycode for H (you can change this accordingly).

answered Aug 04 '10 at 12:37

Den

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Thanks for sharing, but I find Quartermeisters solution cleaner and simpler. – stiank81 Aug 04 '10 at 12:42
Yes, sure! That's why I gave you a +1 :-) – stiank81 Aug 04 '10 at 16:05
Nice! One question though: why would this code produce the letter 'H' instead of 'h'? – florien Nov 18 '18 at 16:39
And also, for special keys (like ä) it returns a false key for me. – florien Nov 18 '18 at 17:20

How do I simulate Text input to a WPF TextBox?

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