Using Enums in Entity Framework Where Clause

Question

So here is what I have for my enum. Really basic. The enum does NOT have a corresponding database table. Rather, whenever a class has a MyEnum property, the database has an int column. That all works fine.

public enum MyEnum : int
{
    Zero = 0,
    One = 1,
    Two = 2
}

This is my class, it has its own table in the database.

public class MyClass
{
    public long MyClassID { get; set; }
    public MyEnum { get; set; }
}

So when I go to pull out a MyClass object, the MyEnum property is set to its corresponding int value, hooray. My problem is when I try to write a query that uses the MyEnum property, I get an error.

public List<MyClass> FindAllOfEnum(MyEnum myEnum)
{
    using (DbContext db = new DbContext())
    {
        return db.MyClasses.Where(x => x.MyEnum == myEnum);
    }
}

// ERROR:
// The specified type member 'MyEnum' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

So I tried writing this Value extension method, but I realized that would only allow me to take out the MyEnum reference on the right-hand side of the comparison, since I can't put the function actually in the lambda expression. What do?

public static class Extensions
{
    public static int Value(this MyEnum myEnum)
    {
        return (int)myEnum;
    }
}

Please use the search facility before you post. There are plenty of questions asking this. — Eranga
– Eranga, Commented Nov 16, 2011 at 0:48
Well then feel free to provide a link along with your snide comment. — Alec
– Alec, Commented Nov 16, 2011 at 8:34

Kissaki · Accepted Answer · 2020-09-16 14:18:15Z

4

This is not supported until next major version of EF (.NET 4.5). Until .NET 4.5 you must pass int to your queries (conversion must be done outside of your query). The best workaround is this.

edited Sep 16, 2020 at 14:18

Kissaki

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answered Nov 16, 2011 at 11:29

Ladislav Mrnka

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Comments

Todd Bellamy · Accepted Answer · 2011-11-16 03:28:31Z

2

Just cast to begin with:

   public List<MyClass> FindAllOfEnum(MyEnum myEnum) 
   { 
      using (DbContext db = new DbContext()) 
      { 
         return db.MyClasses.Where(x => x.MyEnum == (int)myEnum); 
       } 
   }

answered Nov 16, 2011 at 3:28

Todd Bellamy

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4 Comments

Alec Over a year ago

Nope, this would result in the same error I am getting: The specified type member 'MyEnum' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported. Edit: Actually, I get "Operator '=='

Alec Over a year ago

Edit: Actually, I get "Operator '=='cannot be applied to operands of type 'MyEnum' and 'int'". And if I use Object.Equals, then I get the above error.

Todd Bellamy Over a year ago

Right, what I intended there was to compare against the actual column: return db.MyClasses.Where(x => x.mycolumn == (int)myEnum);

Alec Over a year ago

Okay, thanks. That is what I have right now, I was hoping I didn't have to publicly expose the integer value though, alas.

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