using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class WebControls : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Button1.Click += new EventHandler(Button1_Click);
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        String dateString = TextBox1.Text;
        try
        {
            DateTime enteredDate = Convert.ToDateTime(dateString);
            Calendar1.SelectedDate = enteredDate;
            Calendar1.VisibleDate = enteredDate;
            Calendar1.Visible = true;
        }
        catch (FormatException)
        {
            Calendar1.Visible = false;
        }
    }
}