将一个DataTable转变为自定义的DataSet

将一个DataTable转变为自定义的DataSet      
public DataSetUser SettingDs(DataSetUser ds,DataTable tb)
        {
            DataTable Dstable = ds.Tables[0];
            for (int i = 0; i < tb.Rows.Count; i++)
            {
                DataRow row = Dstable.NewRow();
                for (int j = 0; j < tb.Columns.Count; j++)
                {
                    string str = tb.Columns[j].ToString();
                    row[str] = tb.Rows[i][str];
                }
                Dstable.Rows.Add(row);
            }
            return ds;
        }