How to validate leap year for calendar choosing from drop downlists

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VB

Hi ,

I have drop down lists for Month ,day and year .when i select values in drop down the date will be displayed in text box.its working fine..but im unable to validate leap year for February.
can any one help me regarding this.

im using Vb.net and below is my code for drop down list.

If Not IsPostBack Then
           ddlMonth.DataSource = Enumerable.Range(1, 12).[Select](Function(a) New With { _
	.MonthName = DateTimeFormatInfo.CurrentInfo.GetMonthName(a), _
	.MonthNumber = a _
})
ddlMonth.DataBind()
           ddlYear.DataSource = Enumerable.Range(DateTime.Now.Year, 10)
           ddlYear.DataBind()
           ddlYear.Items.Insert(0, New ListItem("--Select Year--", "0"))
           ddlday.DataSource = Enumerable.Range(1, DateTime.DaysInMonth(DateTime.Now.Year, Convert.ToInt32(ddlMonth.SelectedValue))).Reverse()
           ddlday.DataBind()
           ddlYear1.DataSource = Enumerable.Range(DateTime.Now.Year - 9, 10).Reverse()
           ddlYear1.DataBind()
           ddlday1.DataSource = Enumerable.Range(1, DateTime.DaysInMonth(DateTime.Now.Year, Convert.ToInt32(ddlMonth1.SelectedValue))).Reverse()
           ddlday1.DataBind()
           ddlYear1.Items.Insert(0, New ListItem("--Select Year--", "0"))
       End If

Protected Sub ddlYear_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlYear.SelectedIndexChanged, thnKew.DataBinding
thnKew.Text = ddlday.SelectedItem.Text + "/" + ddlMonth.SelectedValue + " /" + ddlYear.SelectedItem.Text()

End Sub