In System.Linq.Dynamic.Select(), how to deal with a null object reference in a simple way?

Question

I am using dynamic LINQ (System.Linq.Dynamic)(you may find description here, http://dynamiclinq.azurewebsites.net/GettingStarted).

The following statement works well

Products.Select("new(ProductName, CategoryID.CategoryName as CategoryName)");

But I accidentally found when CategoryID is null, the results are empty. But I supposed it would return a record such as:

ProductName="Wine", CategoryName="" (or null).

Then I found a way to do so by

Products.Select("new(ProductName, iif(CategoryID==null,\"\",CategoryID.CategoryName) as CategoryName)");

The statement is ugly.

Do you have a better solution?

Thank you in advance,

"new(ProductName, CategoryID==null?null:CategoryID.CategoryName) as CategoryName)" worked. It seems a little simpler and more general to use null, as Cory mentioned. — Ying, May 20 '15 at 02:06
A more ugly sample is : grand==null?null:(grand.parent==null?null:grand.parent.son). — Ying, May 20 '15 at 02:50

score 4 · Answer 1 · edited May 23 '17 at 12:16

4

The only thing I found is here. It isn't clear why the solution was accepted, but what I did see there is that you can do this:

"new(ProductName, iif(CategoryID==null,null,CategoryID.CategoryName) as CategoryName)"

instead of this:

"new(ProductName, iif(CategoryID==null,\"\",CategoryID.CategoryName) as CategoryName)"

It isn't any shorter, but to me it makes the code a bit more readable because you just use null instead of escaping the quotes.

edited May 23 '17 at 12:16

Community

answered May 20 '15 at 01:55

Cory

"new(ProductName, CategoryID==null?null:CategoryID.CategoryName) as CategoryName)" – Ying May 20 '15 at 02:04

1 Answers1