WHERE clause with many criteria in a LINQ query

With POCOs, I use EntityFramework.
Assume my POCOs are specified as follows (simplified):

class Class1
{
    public int ID;
    public int SomeNumber;
}

class Class2
{
    public int ID;
    public int SomeNumber;
}

class Class3
{
    public int ID;
    public int SomeNumber;
}

class SomeClass
{
    public int ID;
    public int? Class1ID;
    public Class1 Class1;
    public int? Class2ID;
    public Class2 Class2;
    public int? Class3ID;
    public Class3 Class3;
}

I want to gather everySomeClass data from the database that is a part of one ofClass1 , Class2 or Class3 where ClassX.SomeNumber equals a certain quantity

This is how the LINQ query I created looks:

Database DB = new Database(); // object context
var result = DB.SomeClass.ToList();

int SomeNumber = 1; // some number
List<SomeClass> retValue = result
    .Where(x =>
        {
            int Number = 0;
            if (x.Class1 != null)
                Number = x.Class1.SomeNumber;
            else if (x.Class2 != null)
                Number = x.Class2.SomeNumber;
            else if (x.Class3 != null)
                Number = x.Class3.SomeNumber;
            return Number == SomeNumber;
        })
    .ToList();

...however retValue contains no records at all.

The answer

I guess I had to be specific.Include due to the fact that lazy loading was deactivated andx.Class1 , x.Class2 and x.Class3 possessed thenull value. I regret not clearly stating that lazy loading was deactivated since it would have made the issue clear.

However, as a result of Ladislav's article, I enhanced my code as follows:

Database DB = new Database(); // object context

int SomeNumber = 1; // some number
List<SomeClass> retValue = DB.SomeClass
    .Include("Class1")
    .Include("Class2")
    .Include("Class3")
    .Where(x =>
        SomeNumber == x.Class1.SomeNumber ||
        SomeNumber == x.Class2.SomeNumber ||
        SomeNumber == x.Class3.SomeNumber)
    .ToList();

I had no idea that LINQ-to-Entities should automatically coalesce null values.