void HandleChanged (object sender, EventArgs e)
{
if (string.IsNullOrEmpty(this.PlaceholderText))
return;
this.PlaceholderLabel.Text = this.PlaceholderText;
this.PlaceholderLabel.Font = this.Font;
this.PlaceholderLabel.Alpha = string.IsNullOrEmpty (this.Text) ? 1 : 0;
this.SetNeedsLayout();
}