Introduction
If you want to get last day of this month , use DateTime structure with AddMonths( ) method. using this method you can get first day of next month. Now, create a new instance of DateTime structure with some parameter like DateTime(Int32, Int32, Int32). This parameterized method Initializes a new instance of the DateTime structure to the specified year, month, and day. Here you can pass integer 1 in day field. Now, you can delete 1 day from current DateTime object using AddDays (-1) method. Now, your object will return last day of current month.<form id="form1" runat="server">
<div>
<asp:Button ID="Button1"
runat="server"
onclick="Button1_Click"
Text="Click"
BackColor="#99CCFF" />
</div>
<asp:Label ID="Label1"
runat="server"
Text="Label"
BackColor="Yellow"></asp:Label>
</form>
Code Behind
protected void Button1_Click(object sender, EventArgs e)
{
DateTime today = DateTime.Today;
DateTime tempDate = today.AddMonths(1);
DateTime tempDate3 = new DateTime(tempDate.Year, tempDate.Month, 1);
DateTime Monthlastday = tempDate3.AddDays(-1);
Label1.Text = "Today : " + today.ToLongDateString();
Label1.Text += "<br /><br />month last day= ";
Label1.Text += Monthlastday.ToLongDateString();
}