Convert genetic List to comma separated string enclosed within quotes using C# and VB.Net

You need to use the foreach loop.

C#

protected void Page_Load(object sender, EventArgs e)
{
    List<string> list1 = new List<string>();
    list1.Add("option1");
    list1.Add("option2");
    list1.Add("option3");
    string allProductId = "";
    foreach (string s in list1)
    {
        allProductId += "'" + s + "', ";
    }
    allProductId = allProductId.Remove(allProductId.Length - 2);
}

VB.Net

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
    Dim list1 As New List(Of String)()
    list1.Add("option1")
    list1.Add("option2")
    list1.Add("option3")
    Dim allProductId As String = ""
    For Each s As String In list1
        allProductId += (Convert.ToString("'") & s) + "', "
    Next
    allProductId = allProductId.Remove(allProductId.Length - 2)
End Sub