Display month number in TextBox on DropDownList change using C# and VB.Net in ASP.Net

Hi akhter,

Check this example. Now please take its reference and correct your code.

HTML

<asp:DropDownList ID="ddlMonthNames" AutoPostBack="true" runat="server"
    OnSelectedIndexChanged="ddlMonthNames_SelectedIndexChanged">
</asp:DropDownList>
<hr />
<asp:TextBox ID="txtMonth" runat="server" />

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        for (int month = 1; month <= 12; month++)
        {
            string monthName = System.Globalization.DateTimeFormatInfo.CurrentInfo.GetMonthName(month);
            ddlMonthNames.Items.Add(new ListItem(monthName, month.ToString().PadLeft(2, '0')));
        }
    }
}

protected void ddlMonthNames_SelectedIndexChanged(object sender, EventArgs e)
{
    txtMonth.Text = Convert.ToInt16(ddlMonthNames.SelectedValue).ToString();
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        For month As Integer = 1 To 12
            Dim monthName As String = System.Globalization.DateTimeFormatInfo.CurrentInfo.GetMonthName(month)
            ddlMonthNames.Items.Add(New ListItem(monthName, month.ToString().PadLeft(2, "0"c)))
        Next
    End If
End Sub

Protected Sub ddlMonthNames_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
    txtMonth.Text = Convert.ToInt16(ddlMonthNames.SelectedValue).ToString()
End Sub

Screenshot