Calculate Date Difference between two Dates when using ASP.Net AJAX Calendar Extender

Refer This!

http://www.aspforums.net/Threads/190554/Solved-Calculate-difference-between-two-dates-in-ASPNet/Replies/2#Replies

Replace the Textbox control to Calander control.

this might help !!

Here I have created sample that takes range of date and give days count of provided Date Range.

I hope this will help you out.

HTML

<div>
<cc1:ToolkitScriptManager runat="server">
</cc1:ToolkitScriptManager>
<table>
    <tr>
        <td>
            <asp:Label Text="Enter Start Date" runat="server" />
        </td>
        <td>
            <asp:TextBox ID="txtStartDate" runat="server" />
            <cc1:CalendarExtender ID="ceStartDate" runat="server" TargetControlID="txtStartDate"
                PopupPosition="Right" Format="dd/MM/yyyy" />
        </td>
    </tr>
    <tr>
        <td>
            <asp:Label Text="Enter End Date" runat="server" />
        </td>
        <td>
            <asp:TextBox ID="txtEndDate" runat="server" />
            <cc1:CalendarExtender ID="ceEndDate" runat="server" TargetControlID="txtEndDate"
                PopupPosition="Right" Format="dd/MM/yyyy" />
        </td>
    </tr>
    <tr style="text-align: center">
        <td colspan="2">
            <asp:Button ID="btnGetDays" runat="server" Text="Get Days" OnClick="CalculateDays" />
        </td>
    </tr>
    <tr>
        <td colspan="2">
            <asp:Label ID="lblDays" runat="server" />
        </td>
    </tr>
</table>
</div>

Namespaces

using System;
using System.Globalization;

Code

protected void CalculateDays(object sender, EventArgs e)
{
    this.CalculateDays();
}

private void CalculateDays()
{
    TimeSpan i = new TimeSpan(0, 0, 0);
    DateTime startDate = Convert.ToDateTime(this.txtStartDate.Text.Trim(), new CultureInfo("en-Gb"));
    DateTime endDate = Convert.ToDateTime(this.txtEndDate.Text.Trim(), new CultureInfo("en-Gb"));
    i += endDate.Subtract(startDate);
    int days = i.Days;
    this.lblDays.Text = "Days Count is : " + days.ToString();
}

Screenshot