Custom Property validation message code in User Control

Question

How to add a validation code for a custom Property defined in a UserControl . Consider the following piece of code:

 public class Date

{
    private int month = 7;  // Backing store 

    public int Month
    {
        get
        {
            return month;
        }
        set
        {
            if ((value > 0) && (value < 13))
            {
                month = value;
            }
        }
    }
}

It will check that Month value be between 1 and 12, but I want to an Invalid input message be shown up too in case it's invalid. Any ideas ?

Answer 1

If value is not between 1 and 12 you can throw eg an InvalidOperationException and handle it in your main thread.

public int Month
{
    get
    {
        return month;
    }
    set
    {
        if ((value > 0) && (value < 13))
        {
            month = value;
        }
        else throw new InvalidOperationException("Invalid month");
    }
}

Then something like...

private void textBox1_Validating(object sender, CancelEventArgs e)
{
   try
   {
      date.Month = Convert.ToInt32(textbox1.Text);
   }
   catch(InvalidOperationException ex)
   {
      e.Cancel = true;
      textBox1.Select(0, textBox1.Text.Length);

      // some message about invalid value
   }
}

where textBox1_Validating is the validating event handler of the textbox.