c# dataTable Simple instance of merge two columns into a new column

public static DataTable UniteDataTableColumns(DataTable dt, String newColumnName, string ColumnName1, string ColumnName2)
        {
//Summary expressions
            string expression = "";                            
            expression = ("{0}+'('+{1}+')'", ColumnName1, ColumnName2);          
//Add a summary column
            myDataType = ("");
            DataColumn dcCol = new DataColumn(newColumnName, myDataType, expression, );
//Add merged columns
            (dcCol);
            return dt;
        }