Comparing a generic against null that could be a value or reference type?

Question

public void DoFoo(T foo) where T : ISomeInterface
{
    //possible compare of value type with \'null\'.
    if (foo == null) throw new ArgumentNull         


        

Answer 1

No, there won't be any problems, but if you want the warning to disappear, you can use the following:

public void DoFoo(T foo) where T : ISomeInterface
{
    if (ReferenceEquals(foo, null)) throw new ArgumentNullException("foo");
}

Alternatively you can do something like this:

// when calling this with an actual T parameter, you have to either specify the type
// explicitly or cast the parameter to T?.
public void DoFoo(T? foo) where T : struct, ISomeInterface
{
    if (foo == null)
    {
        // throw...
    }

    DoFooInternal(foo.Value);
}

public void DoFoo(T foo) where T : class, ISomeInterface
{
    if (foo == null)
    {
        // throw...
    }

    DoFooInternal(foo); 
}

private void DoFooInternal(T foo) where T : ISomeInterface
{
    // actual implementation
}