using System . Runtime . InteropServices;
[ DllImport ( "User32.dll" )]
static extern int SetWindowLong( IntPtr hWnd, int nIndex, int dwNewLong);
[ DllImport ( "User32.dll" )]
static extern int GetWindowLong( IntPtr hWnd, int nIndex);
public const int GWL_STYLE = - 16 ;
public const int ES_NUMBER = 0x2000 ;
private void Form1_Load( object sender , EventArgs e)
{
SetWindowLong(textBox1 . Handle, GWL_STYLE,
GetWindowLong(textBox1 . Handle, GWL_STYLE) | ES_NUMBER);
}
// or
private void textBox1_KeyPress( object sender , KeyPressEventArgs e)
{
e . Handled = "0123456789" . IndexOf(e . KeyChar) < 0 ;
}