Thank you all for helping me i got solution using below code
objResult.ResutlDs.Tables[0].Columns.Add("Cast", typeof(string));
for (int i = 0; i < objResult.ResutlDs.Tables[0].Rows.Count; i++)
{
objResult.ResutlDs.Tables[0].Rows[i]["Cast"] = objResult.ResutlDs.Tables[2].Rows[i]["Cast"];
}