Using ternary operator to check if null - null reference is not the same as null

Question

I am attempting to use the ternary operator to check if a value is null and return one expression or the other. What I'm experiencing when incorporating this into a LINQ expression is that the Transact-SQL translation of the LINQ expression attempts to do a "column = null" rather than a "column IS NULL". I have reason to believe that this is because I'm doing the following:

mappedColumnName == (myVar == null ? null : myOtherVar)

Since it translates the following to columnName IS NULL in Transact-SQL:

mappedColumnName == null

Does anyone have any experience with this? I'd very much like to get this to work.

The entire LINQ expression:

(from MenuItem in menuContext.Menus
   where MenuItem.IsSysAdmin == (ClientID == 1 ? true : false)
   && MenuItem.IsActive == true
   && MenuItem.ParentMenuCode == (ActiveSubMenu==null?null:ActiveMenu)
   && MenuItem.ClientID == (UseClientMenu ? ClientID : 0)
   && MenuItem.EmployeeID == (UseEmployeeMenu ? EmployeeID : 0)
   orderby MenuItem.SortOrder, MenuItem.MenuName
   select MenuItem);

Check this: [stackoverflow.com/questions/5224339/… [1]: stackoverflow.com/questions/5224339/… — Vitaliy
– Vitaliy, Commented Dec 4, 2012 at 10:19
Vitality: I'm not sure that'll work. I want to check if ParentMenuCode is null only if ActiveSubMenu is null, if it's not null I want to check if ParentMenuCode is equal to ActiveMenu. — Maritim
– Maritim, Commented Dec 4, 2012 at 10:22

happygilmore · Accepted Answer · 2012-12-04 11:09:20Z

4

Why don't you use

mappedColumnName == (myVar == null ? DBNull.Value: myOtherVar)

instead?

answered Dec 4, 2012 at 11:09

happygilmore

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Jamie · Accepted Answer · 2012-12-04 10:17:49Z

1

I've never actually attempted to use ternary operators in linq although you could write it as:

(
    (myVar == null && mappedColumnName == null      ) ||
    (myVar != null && mappedColumnNmae == myOtherVar)
)

answered Dec 4, 2012 at 10:17

Jamie

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1 Comment

Maritim Over a year ago

Thank you Jamie! This works, the workaround is also referenced at stackoverflow.com/questions/2097539/…

Jayant Varshney · Accepted Answer · 2012-12-04 10:26:37Z

0

try this

(from MenuItem in menuContext.Menus
   where MenuItem.IsSysAdmin == ((ClientID == 1 )? true : false)
   && MenuItem.IsActive == true
   && MenuItem.ParentMenuCode == ( (ActiveSubMenu==null) ?null:ActiveMenu)
   && MenuItem.ClientID == (UseClientMenu ? ClientID : 0)
   && MenuItem.EmployeeID == (UseEmployeeMenu ? EmployeeID : 0)
   orderby MenuItem.SortOrder, MenuItem.MenuName
   select MenuItem);

answered Dec 4, 2012 at 10:26

Jayant Varshney

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1 Comment

Maritim Over a year ago

Same result. The Transact-SQL translation of the ternary expression is a scalar method and Transact-SQL basically tries to perform columnName = null which will always fail.

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