C# Get Object Size

GetObjectSize.cs

public class GetObjectSize
    {
        public enum SetValueEnum
        {
            NotSet = -1,
            Yes    = 1,
            No     = 0
        }
        private SetValueEnum _isPrimitive;
        private int          _primitiveSize;
        private Type         _type;
        public int GetSize(object obj)
        {
            if(_type == null)
                _type = obj.GetType();
            if(_isPrimitive == SetValueEnum.NotSet)
                _isPrimitive = IsValidPrimitive(_type) ? SetValueEnum.Yes : SetValueEnum.No;
            if(_isPrimitive == SetValueEnum.Yes)
                return _primitiveSize;
            return Converters.GetBytesObject(obj, _type).Length;
        }
        public bool IsValidPrimitive(Type type)
        {
            switch(Type.GetTypeCode(type))
            {
                case TypeCode.Boolean:
                    _primitiveSize = sizeof(bool);
                    return true;
                case TypeCode.Char:
                    _primitiveSize = sizeof(char);
                    return true;
                case TypeCode.SByte:
                    _primitiveSize = sizeof(sbyte);
                    return true;
                case TypeCode.Byte:
                    _primitiveSize = sizeof(byte);
                    return true;
                case TypeCode.Int16:
                    _primitiveSize = sizeof(short);
                    return true;
                case TypeCode.UInt16:
                    _primitiveSize = sizeof(ushort);
                    return true;
                case TypeCode.Int32:
                    _primitiveSize = sizeof(int);
                    return true;
                case TypeCode.UInt32:
                    _primitiveSize = sizeof(uint);
                    return true;
                case TypeCode.Single:
                    _primitiveSize = sizeof(float);
                    return true;
                case TypeCode.Object:
                    return false;
                case TypeCode.DateTime:
                    unsafe
                    {
                        _primitiveSize = sizeof(DateTime);
                    }
                    return true;
                case TypeCode.String:
                    return false;
                case TypeCode.Int64:
                    _primitiveSize = sizeof(long);
                    return true;
                case TypeCode.UInt64:
                    _primitiveSize = sizeof(ulong);
                    return true;
                case TypeCode.Double:
                    _primitiveSize = sizeof(double);
                    return true;
                case TypeCode.Decimal:
                    _primitiveSize = sizeof(decimal);
                    return true;
                default:
                    return false;
            }
        }
    }