C# – Value Type Equals method – why does the compiler use reflection?

by

The following is the decompiled ValueType.Equals method from mscorlib:

public override bool Equals(object obj)
{
    if (obj == null)
    {
        return false;
    }
    RuntimeType type = (RuntimeType) base.GetType();
    RuntimeType type2 = (RuntimeType) obj.GetType();
    if (type2 != type)
    {
        return false;
    }
    object a = this;
    if (CanCompareBits(this))
    {
        return FastEqualsCheck(a, obj);
    }
    FieldInfo[] fields = type.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
    for (int i = 0; i < fields.Length; i++)
    {
        object obj3 = ((RtFieldInfo) fields[i]).InternalGetValue(a, false);
        object obj4 = ((RtFieldInfo) fields[i]).InternalGetValue(obj, false);
        if (obj3 == null)
        {
            if (obj4 != null)
            {
                return false;
            }
        }
        else if (!obj3.Equals(obj4))
        {
            return false;
        }
    }
    return true;
}

When possible, a bit-wise comparison will be done (note the CanCompareBits and FastEqualsCheck, both of which are defined as InternalCall. The JIT would presumably inject the appropriate code here. As to why it is so slow, I couldn’t tell you.

More Related Contents:

  1. Why are mutable structs “evil”?
  2. When should I use a struct rather than a class in C#?
  3. Error: “Cannot modify the return value” c#
  4. Structs versus classes
  5. Changing the value of an element in a list of structs
  6. Non-unique enum values
  7. Generic constraints, where T : struct and where T : class
  8. How does native implementation of ValueType.GetHashCode work?
  9. implicit operator using interfaces
  10. Immutability of structs [duplicate]
  11. Modify Struct variable in a Dictionary
  12. Delegate caching behavior changes in Roslyn
  13. How does creating a instance of class inside of the class itself works?
  14. Can structs contain fields of reference types
  15. C# compiler bug? Why doesn’t this implicit user-defined conversion compile?
  16. Which is best for data store Struct/Classes?
  17. Non-read only alternative to anonymous types
  18. Could not load file or assembly … The parameter is incorrect
  19. Marshal C++ struct array into C#
  20. Compiler Value Type Resolution and Hardcoded “0” Integer Values
  21. TargetedPatchingOptOut: “Performance critical to inline across NGen image boundaries”?
  22. Why can’t I use the array initializer with an implicitly typed variable?
  23. Mono Compiler as a Service (MCS)
  24. How do generics get compiled by the JIT compiler?
  25. Why is it possible to instantiate a struct without the new keyword?
  26. Cycle in the struct layout that doesn’t exist
  27. C# Compiler optimization – Unused methods
  28. Why and how does C# allow accessing private variables outside the class itself when it’s within the same containing class?
  29. Are structs ‘pass-by-value’?
  30. Inline property initialisation and trailing comma

Leave a Comment