Numeric Textbox

No easy way to make a "numbers" only TextBox with .NET CF on the SmartPhones. There are two easy ways of adding this, one simply traps keypresses on a custom TextBox and the other uses Platform Invoke.

(1) from http://forums.microsoft.com/msdn/ShowPost.aspx?PostID=47854

// in InitializeComponents, add this event handler.
this.textBox1.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.NumbericTextValidator);

// now this is the event handler's method.
private void NumbericTextValidator(
object sender,
System.Windows.Forms.KeyPressEventArgs e)
{
if ("0123456789".IndexOf(e.KeyChar) > -1)
e.Handled = false;
else
e.Handled = true;
}

(2) http://www.devx.com/wireless/Article/21291/1763

This solution uses Platform Invoke, which has the advantage of actually changing the text input mode icon in the upper right hand corner of the SMT5600 (e.g. T9, abc, 123, etc.).

(3) Something similar over at opennetcf.org.

Update (April 24th, 2006): In .NET CF 2.0 this is easy.
For CF 2.0 (Windows Mobile 5.0 Smartphone):
using Microsoft.WindowsCE.Forms; //at the top
InputModeEditor.SetInputMode(textBox1, InputMode.Numeric); //somewhere in your code

(from link)