A Calendar control example for Selecting dates from database, Disabling old dates selection, and Selecting multiple dates. This application is meant for beginners.

This example is done in a very easy to understand way to help beginners customize the Calendar control.

using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;
using System.Collections.Generic;
using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page
{

///////////// Selecting multiple dates //////////////////

public static List UserSelectedDays = new List();

////////////_____________________________///////////////

protected void Page_Load(object sender, EventArgs e)
{

////////////////////////////// Selecting dates from database //////////////////////////////

string SqlConStr = System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionString1"].ConnectionString;
SqlConnection Sqlcon = new SqlConnection(SqlConStr);
SqlDataAdapter SqlDA = new SqlDataAdapter("Select * From HolidayDate", Sqlcon);
DataSet dsPubs = new DataSet("Pubs");

SqlDA.FillSchema(dsPubs, SchemaType.Source, "Holiday");
SqlDA.Fill(dsPubs, "Holiday");
DataTable tblAuthors;
tblAuthors = dsPubs.Tables["Holiday"];

foreach (DataRow drCurrent in tblAuthors.Rows)
{

int day, month, year;

day = Convert.ToInt32(drCurrent["day"]);
month = Convert.ToInt32(drCurrent["month"]);
year = Convert.ToInt32(drCurrent["year"]);

SelectedDatesCollection theDates = Calendar1.SelectedDates;
theDates.Add(new DateTime(year, month, day));

}

//////////////////////_____________________________________________////////////////////////////

}
protected void ClearSelectedDates_Click(object sender, EventArgs e)
{
Calendar1.SelectedDates.Clear();
UserSelectedDays.Clear();
}
protected void Calendar1_DayRender(object sender, DayRenderEventArgs e)
{

//////////// Disabling old dates selection ///////////////

if (e.Day.Date = DateTime.Now.Date)
{
e.Cell.BackColor = System.Drawing.ColorTranslator.FromHtml("#a9a9a9");
e.Day.IsSelectable = false;
}

/////////_____________________________________________//////////

///////////// Selecting multiple dates //////////////////

if (e.Day.IsSelected == true)
{
UserSelectedDays.Add(e.Day.Date);
}
}
protected void Calendar1_SelectionChanged(object sender, EventArgs e)
{

///////////// Selecting multiple dates //////////////////

foreach (DateTime SelectedDays in UserSelectedDays)
{
Calendar1.SelectedDates.Add(SelectedDays);
}

////////////_____________________________///////////////

}
}