What should I do about “Possible compare of value type with 'null'”?

Question

While writing this method for a custom NUnit Constraint.

    private void AddMatchFailure(string failureName, TExpected expected, TActu         


        

Answer 1

What are the rules when comparing a ValueType to null and how should I write the method to account for that without limiting the generic parameters by adding a class constraint?

If you do not know that they will be reference types, then you can say

private void AddMatchFailure(
    string failureName,
    TExpected expected,
    TActual actual
) {
    _matchFailures.Add(
        String.Format(MatchFailureFormat, failureName,
        IsDefault(expected) ? DefaultStringForType() : expected.ToString(),
        IsDefault(actual) ? DefaultStringForType() : actual.ToString()
    );
}

private bool IsDefault(T value) {
    if(typeof(T).IsValueType) {
        return default(T).Equals(value);
    }
    else {
        return Object.Equals(null, value);
    }
}

private string DefaultStringForType() {
    if(typeof(T).IsValueType) {
        return default(T).ToString();
    }
    else {
        return "null";
    }
}