CODEWITHSUNDEEP
c#linq
Kjensen
Kjensen

Reputation: 12374

SELECT NEW with a potentially null field using LINQ and Entity Framework

I want to quickly select some rows, format it nicely for a dropdownlist/selectlist or something like that - but I have a field in the db, that is nullable (DateOfBirth).

var athletes = (from at in _db.Athletes
           select new{
                  Name = at.Name + " " + at.DateOfBirth, 
                  Id = at.AthleteId 
                  }).ToList();

Is there a way to handle nullable types inside the LINQ in a case like this?

Edit:

I was not paying attention to the fact, that since this is using entity framework, methods that work with standard LINQ cannot be used unless they have a SQL translation.

Upvotes: 5

Views: 11212

Answers (4)

pmereles
pmereles

Reputation: 421

In VB.NET

Dim athletes = (From at In _db.Athletes
       Select New With{
              .Name = at.Name + " " + If(at.Field(Of Object)("DateOfBirth") = Nothing, string.Empty, at.Field(Of Object)("DateOfBirth")), 
              .Id = at.AthleteId 
              }).ToList()

Upvotes: 0

Steve Danner
Steve Danner

Reputation: 22148

Since you are just doing string appending try this.

var athletes = (from at in _db.Athletes
           select new{
                  Name = at.Name + " " + (at.DateOfBirth ?? string.Empty), 
                  Id = at.AthleteId 
                  }).ToList();

Upvotes: 2

David Mårtensson
David Mårtensson

Reputation: 7600

Often a nullable can be handled using variable ?? default

var res = nullableVariable ?? defaultValue;

But be carefull with datetime, linq will try to implement this in SQL and DateTime.MinValue from C# is not within the valid range for SQL and will give you an error message.

Upvotes: 2

Shan Plourde
Shan Plourde

Reputation: 8706

You can use the null coalesce operator, see Equivalent of SQL ISNULL in LINQ?.

Something like:

var athletes = (from at in _db.Athletes
           select new{
                  Name = at.Name + " " + (at.DateOfBirth ?? ""), 
                  Id = at.AthleteId 
                  }).ToList();

Upvotes: 7

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