Disable particluar Date(s) from the Calender Control.

protected void Calendar1_DayRender(object sender, DayRenderEventArgs e)
{
//Here whatever user pass the date into textbox then it will parse that date as DateTime…
DateTime myDateTime = DateTime.Parse(txtUserDate.Text);
if (e.Day.Date == myDateTime)
{
//Disable Given Date....
e.Day.IsSelectable = false;
}
}