Display an image on calendar control in a particular date in asp.net using C#

You can use dayRender event of calendar control
protected void Calendar1_DayRender(object sender, DayRenderEventArgs e)
{
if (e.Day.Date == DateTime.Today)
{
Image imageobject= new Image();
img.ImageUrl = @"~\images\test1.gif";
e.Cell.Controls.Add(img);
}
}
This code will show image for the current date.