Question

Given a class

[Table ( Name = "AllPlayerInfo" ) ]
public class AllPlayerInfo
{
   [Column (IsPrimaryKey = true)]
   public decimal Classes_ID { get; set; }
   [Column (IsPrimaryKey = true)]
   public decimal Member_ID { get; set; }
   //...
}

I call

DataContext db2 = new DataContext ( sqlconnectstring );
Table<AllPlayerInfo> api = db2.GetTable<AllPlayerInfo> ();

which returns all the records from the database table.
I look at the contents of api and confirm that the record I want is there and has Member_ID == 4617.

So I issue following command:

AllPlayerInfo attempt1 = api.Where ( r => r.Member_ID == 4617).FirstOrDefault<AllPlayerInfo> ();

that (incorrectly) returns null.

So then I transfer the object to a list:

List<AllPlayerInfo> listapi = api.ToList<AllPlayerInfo> ();

and then use the Exists method and it does find the record I wanted:

bool recordexists = listapi.Exists ( r => r.Member_ID == 4617 );

recordexists is true!

So the question is: Why does the Where method not find the record when it is clearly there? I did try the Where method with other fields and values and they worked. Just not this particular field. I tested other decimal fields such as the class_id and it worked.

Answer 1

I would check the generated SQL in SQL profiler. Sometimes when LINQ to SQL determines you are comparing incorrect types, e.g. Where(x => x.somestring == null) and x.somestring is not set as nullable in the DBML file then it generates SQL with a where clause that says WHERE 1=0 and then goes off and runs that in SQL server which will boviously return no records. Member ID is a decimal and it is probably inerpretting your literal as an int so it has decided that Where( r => r.Member_ID == 4617) cannot ever be true so it creates SQL that will never return any records.