public override DbExpression Visit(DbIsNullExpression expression) { EntityUtil.CheckArgumentNull(expression, "expression"); return(VisitUnary(expression, exp => { if (TypeSemantics.IsRowType(exp.ResultType)) { // return CqtBuilder.CreateIsNullExpressionAllowingRowTypeArgument(exp); } else { return CqtBuilder.IsNull(exp); } } )); }