I get the below error Unable to cast object of type 'System.String' to type 'System.Data.DataTable'. This is the code I'm using Dim str As String = String.Empty If (Session("Brief") IsNot Nothing) Then Dim dt As DataTable = Session("Brief") If (dt.Rows.Count > 0) Then For Each dr As DataRow In dt.Rows If (str.Length > 0) Then str += "," str += dr("talentID").ToString() Next End If End If Return str Thanks