C#

public byte[] Binary(string key)
{
    ResourceManager resManager = new ResourceManager("[ASSEMBLYNAME]", This.GetType().Assembly);
      return (byte[]) resManager.GetObject(key);
   }

private void TextBox_Validating(object sender, CancelEventArgs e)
{
    TextBox textBox = sender as TextBox;
    if(textBox == null)  // Ensure this is indeed a TextBox
        return;
 
    // Allow the user to leave the text box without typing anything
    if(textBox.TextLength == 0)
        return;
 
    bool error = false;
 
    try
    {
        int n = Convert.ToInt32(textBox);
        if(n < 0 || n > 100)  // Check range if necessary
            error = true;
    }
    catch(FormatException)
    {
        // Could not parse the number
        error = true;
    }
    finally
    {
        if(error)
        {
            MessageBox.Show("Please enter a valid number");
 
            textBox.SelectAll();
            textBox.Focus();
 
            e.Cancel = true;  // Don't allow focus to leave the control
        }
    }
}