Bind DropDownList with Dates in ASP.Net GridView for selected Month and Year using C# and VB.Net

Hi learningmrs,

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

HTML

<asp:DropDownList runat="server" ID="ddlMonths">
    <asp:ListItem Text="Select" Value="0" />
    <asp:ListItem Text="January" Value="1" />
    <asp:ListItem Text="February" Value="2" />
    <asp:ListItem Text="March" Value="3" />
</asp:DropDownList>
<asp:DropDownList runat="server" ID="ddlYears">
    <asp:ListItem Text="Select" Value="0" />
    <asp:ListItem Text="2020" Value="2020" />
    <asp:ListItem Text="2021" Value="2021" />
    <asp:ListItem Text="2022" Value="2022" />
</asp:DropDownList>
<asp:Button Text="Save" runat="server" OnClick="OnSave" />
<hr />
<asp:GridView runat="server" ID="gvDetails" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
    <Columns>
        <asp:TemplateField HeaderText="Days">
            <ItemTemplate>
                <asp:DropDownList runat="server" ID="ddlDays">
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="Month" HeaderText="Month" />
        <asp:BoundField DataField="Year" HeaderText="Year" />
    </Columns>
</asp:GridView>

Code

C#

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        DropDownList ddlDays = e.Row.FindControl("ddlDays") as DropDownList;
        List<ListItem> days = new List<ListItem>();
        for (int i = 1; i <= DateTime.DaysInMonth(Convert.ToInt32(ddlYears.SelectedValue), Convert.ToInt32(ddlMonths.SelectedValue)); i++)
        {
            days.Add(new ListItem { Value = i.ToString(), Text = i.ToString() });
        }
        ddlDays.DataSource = days;
        ddlDays.DataTextField = "Text";
        ddlDays.DataValueField = "Value";
        ddlDays.DataBind();
    }
}

protected void OnSave(object sender, EventArgs e)
{
    System.Data.DataTable dt = new System.Data.DataTable();
    dt.Columns.Add("Month");
    dt.Columns.Add("Year");
    dt.Rows.Add(ddlMonths.SelectedItem.Text, ddlYears.SelectedItem.Text);
    gvDetails.DataSource = dt;
    gvDetails.DataBind();
}

VB.Net

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim ddlDays As DropDownList = TryCast(e.Row.FindControl("ddlDays"), DropDownList)
        Dim days As List(Of ListItem) = New List(Of ListItem)()
        For i As Integer = 1 To DateTime.DaysInMonth(Convert.ToInt32(ddlYears.SelectedValue), Convert.ToInt32(ddlMonths.SelectedValue))
            days.Add(New ListItem With { 
                .Value = i.ToString(),
                .Text = i.ToString()
            })
        Next

        ddlDays.DataSource = days
        ddlDays.DataTextField = "Text"
        ddlDays.DataValueField = "Value"
        ddlDays.DataBind()
    End If
End Sub

Protected Sub OnSave(ByVal sender As Object, ByVal e As EventArgs)
    Dim dt As System.Data.DataTable = New System.Data.DataTable()
    dt.Columns.Add("Month")
    dt.Columns.Add("Year")
    dt.Rows.Add(ddlMonths.SelectedItem.Text, ddlYears.SelectedItem.Text)
    gvDetails.DataSource = dt
    gvDetails.DataBind()
End Sub

Screenshot