Get multiple selected values with comma separated from ListBox control using C# in ASP.Net

Hi sudhir,

I have created sample please refer below code.

HTML

<asp:ListBox ID="ddlCourse" runat="server" Width="200px" SelectionMode="Multiple">
    <asp:ListItem Text="BE" Value="1" />
    <asp:ListItem Text="B.Tech" Value="2" />
    <asp:ListItem Text="BSc." Value="3" />
    <asp:ListItem Text="MSc." Value="4" />
</asp:ListBox>
<br />
<asp:Button Text="Get Selected Item" runat="server" OnClick="GetSelectedItem" />

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        ddlCourse.Items.Insert(0, "--SELECT--");
    }
}

protected void GetSelectedItem(object sender, EventArgs e)
{
    string courses = string.Empty;
    foreach (ListItem item in ddlCourse.Items)
    {
        if (item.Selected)
        {
            courses += item.Text + ",";
        }
    }
    Response.Write(courses.Remove(courses.Length - 1));
}

Screenshot