C# is value part of Enum

Question

I found an edge case for enum values and want to know whether there is a solution for that problem in .net5

I´ve got the following enum:

public enum SomeEnum : ushort
{
    FirstValue = 0x9D80,
    SecondValue = 0x9DCE,
    ThirdValue = 0xEBA0,
    Unknown = 0xFFFF,
}

And want to know whether a given value is part of the enum and used Enum.TryParse but with the following Code it will always return true even 1 is not part of the enum:

Enum.TryParse<SomeEnum>("1", out _);

Thats because the following line does not corse an error:

var myEnum = (SomeEnum)1;

So I´ve changed to the Method Enum.IsDefined, so far so good the following code does deliver the desired results:

Enum.TryParse<SomeEnum>(myValue, out var x) && Enum.IsDefined(x);

But now the edge case is:

var myEnumValue = uint.Max;
Enum.TryParse<SomeEnum>(myValue.ToString(), out var x) && Enum.IsDefined(x);

Which delivers true because x = SomeEnum.Unknown and thats caused because IsDefined does a cast to ushort from uint.Max which is 0xFFFFFFFF to 0xFFFF. So I do not know how to check for any case whether a numeric value is part of a given enum.