Populate Months based on Year using C# in ASP.Net

theuncle...

SOLVED CLOSED ACTIVE ANSWERED
User: theunclevince
Posted: on Mar 03, 2025 01:38 AM
Forum: Data Controls
Answer: 1
Views: 277
Sample Code: Download

Hello everyone,

In my drop down list ddlmonth I need to display the months between August to December for the year 2024, while for 2025 I need to display all the months progressively with respect to the current month.

I mean:

if we are in February 2025, I only need to display the month of January 2025, if we are in March 2025 I need to display the months of January and February 2025, if we are in April 2025 I need to display the months of January, February and March 2025, etc.

Today, March 2025 I tried this code but I only see February 2025 and January 2025 has disappeared

DateTime dateTime = DateTime.Now;
List<ListItem> months = new List<ListItem>();
 
if (ddlyear.SelectedValue == "2024")
{
    for (int i = 2; i <= 8; i++)
    {
        months.Add(ddlmonth.Items.Cast<ListItem>()
                        .Where(x => x.Value.Equals(dateTime.AddMonths(-i).Month.ToString()))
                        .FirstOrDefault());
    }
}
else
{
    for (int i = 1; i <= 2; i++)
    {
 
        months.Add(ddlmonth.Items.Cast<ListItem>()
                        .Where(x => x.Value.Equals(dateTime.AddMonths(-i).Month.ToString()))
                        .FirstOrDefault());
    }
}
 
//Determines first item i.e.Equals Default Item.
ListItem defaultItem = ddlmonth.Items[0];
 
//Clears all items in the DropDownList.
ddlmonth.Items.Clear();
 
//Reverse the List of last two months.
months.Reverse();
 
//Inserts Default Item.
months.Insert(0, defaultItem);
 
//Assigning month to DropDownList.
ddlmonth.DataSource = months;
ddlmonth.DataTextField = "Text";
ddlmonth.DataValueField = "Value";
ddlmonth.DataBind();

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dharmend...

0 2

Reply
ANSWER
User: dharmendr
Replied: on Mar 03, 2025 12:16 PM
Modified: on Mar 06, 2025 10:51 AM
Report

Hi theunclevince,

Add months dynamically to the DropDownList as some of the months may not available on year change.

Refer below code.

HTML

<div>
    <asp:DropDownList ID="ddlyear" runat="server">
        <asp:ListItem Text="Select" Value=""></asp:ListItem>
        <asp:ListItem Text="2025" Value="2025" Selected="True"></asp:ListItem>
        <asp:ListItem Text="2024" Value="2024"></asp:ListItem>
    </asp:DropDownList>
</div> 
<br /> 
<div>
    <asp:DropDownList ID="ddlmonth" 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>
</div>

Code

ddlmonth.Items.Clear();
for (int month = 1; month <= 12; month++)
{
    string monthName = DateTimeFormatInfo.CurrentInfo.GetMonthName(month).ToUpper().Substring(0, 3);
    ddlmonth.Items.Add(new ListItem(monthName, month.ToString()));
}
ddlmonth.Items.Insert(0, new ListItem("Select", ""));
 
DateTime dateTime = DateTime.Now;
List<ListItem> months = new List<ListItem>();
 
if (ddlyear.SelectedValue == "2024")
{
    for (int i = 12; i >= 8; i--)
    {
        months.Add(ddlmonth.Items[i]);
    }
}
else
{
    for (int i = 1; i < DateTime.Now.Month; i++)
    {
        months.Add(ddlmonth.Items[i]);
        months.Reverse();
    }
}
 
//Determines first item i.e.Equals Default Item.
ListItem defaultItem = ddlmonth.Items[0];
 
//Clears all items in the DropDownList.
ddlmonth.Items.Clear();
 
//Reverse the List of last two months.
months.Reverse();
 
//Inserts Default Item.
months.Insert(0, defaultItem);
 
//Assigning month to DropDownList.
ddlmonth.DataSource = months;
ddlmonth.DataTextField = "Text";
ddlmonth.DataValueField = "Value";
ddlmonth.DataBind();

Screenshot

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Populate Months based on Year using C# in ASP.Net

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