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How can I restrict the characters that my textbox can accept

Platform: WinForms| Category: TextBox

You can handle the textbox’s KeyPress event and if the char passed in is not acceptable, mark the events argument as showing the character has been handled. Below is a derived TextBox that only accepts digits (and control characters such as backspace, …). Even though the snippet uses a derived textbox, it is not necessary as you can just add the handler to its parent form.

public class NumbersOnlyTextBox : TextBox
	public NumbersOnlyTextBox()
		this.KeyPress += new KeyPressEventHandler(HandleKeyPress);

	private void HandleKeyPress(object sender, KeyPressEventArgs e)
		if(!char.IsDigit(e.KeyChar) && !char.IsControl(e.KeyChar))
			e.Handled = true;

Public Class NumbersOnlyTextBox
	Inherits TextBox
	Public Sub New()
		AddHandler Me.KeyPress, AddressOf HandleKeyPress
	End Sub ’New
	Private Sub HandleKeyPress(sender As Object, e As KeyPressEventArgs)
		If Not Char.IsDigit(e.KeyChar) And Not Char.IsControl(e.KeyChar) Then
			e.Handled = True
		End If
	End Sub ’HandleKeyPress
End Class ’NumbersOnlyTextBox

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