Order by month number using linq in C# ASP.Net

Hi theunclevince,

Use OrderByDescending as done in the sample.

Here is the updated code.

HTML

<asp:DropDownList ID="ddlMonths" runat="server">
    <asp:ListItem Text="Select" Value=""></asp:ListItem>
    <asp:ListItem Text="Jan" Value="1"></asp:ListItem>
    <asp:ListItem Text="Feb" Value="2"></asp:ListItem>
    <asp:ListItem Text="Mar" Value="3"></asp:ListItem>
    <asp:ListItem Text="Apr" Value="4"></asp:ListItem>
    <asp:ListItem Text="May" Value="5"></asp:ListItem>
    <asp:ListItem Text="Jun" Value="6"></asp:ListItem>
    <asp:ListItem Text="Jul" Value="7"></asp:ListItem>
    <asp:ListItem Text="Aug" Value="8"></asp:ListItem>
    <asp:ListItem Text="Sep" Value="9"></asp:ListItem>
    <asp:ListItem Text="Oct" Value="10"></asp:ListItem>
    <asp:ListItem Text="Nov" Value="11"></asp:ListItem>
    <asp:ListItem Text="Dec" Value="12"></asp:ListItem>
</asp:DropDownList>

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    DateTime dateTime = new DateTime(2025, 02, 10);

    // List of Months to be display.
    List<ListItem> months = new List<ListItem>();
    for (int i = 1; i <= 2; i++)
    {
        months.Add(ddlMonths.Items.Cast<ListItem>()
                            .Where(x => x.Value.Equals(dateTime.AddMonths(-i).Month.ToString()))
                            .FirstOrDefault());
    }

    // Keep Default item.
    ListItem defaultItem = ddlMonths.Items[0];

    // Clear DropDownList Items.
    ddlMonths.Items.Clear();

    // Reverse the Items.
    months = months.OrderByDescending(m => m.Value.PadLeft(2, '0')).ToList();

    // Add default item as 1st item.
    months.Insert(0, defaultItem);

    // Set the Datasource.
    ddlMonths.DataSource = months;
    ddlMonths.DataTextField = "Text";
    ddlMonths.DataValueField = "Value";
    ddlMonths.DataBind();
}

VB.Net

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    Dim dateTime As New DateTime(2025, 2, 10)

    ' List of Months to be displayed.
    Dim months As New List(Of ListItem)()
    For i As Integer = 1 To 2
        months.Add(ddlMonths.Items.Cast(Of ListItem)().Where(Function(x)
                                                                    Return x.Value.Equals(dateTime.AddMonths(-i).Month.ToString())
                                                                End Function).FirstOrDefault())
    Next

    ' Keep Default item.
    Dim defaultItem As ListItem = ddlMonths.Items(0)

    ' Clear DropDownList Items.
    ddlMonths.Items.Clear()

    ' Reverse the Items.
    months = months.OrderByDescending(Function(m) m.Value.PadLeft(2, "0")).ToList()

    ' Add default item as 1st item.
    months.Insert(0, defaultItem)

    ' Set the Datasource.
    ddlMonths.DataSource = months
    ddlMonths.DataTextField = "Text"
    ddlMonths.DataValueField = "Value"
    ddlMonths.DataBind()
End Sub

Screenshot