Check if exclusively only these flags set in enumeration

Question

I have created an extension method as such..

public static bool AllFlagsSet<T>(this T input, params T[] values) where T : struct, IConvertible
{
    bool allSet = true;
    int enumVal = input.ToInt32(null);

    foreach (T itm in values)
    {
        int val = itm.ToInt32(null);
        if (!((enumVal & val) == val)) 
        {
            allSet = false;
            break;
        }
    }

    return allSet;
}

Which works great for the purposes I needed, however I now have a requirement to create a method with the same signature which checks if only exclusively those values have been set.

Basically something like this.

public static bool OnlyTheseFlagsSet<T>(this T input, params T[] values) where T : struct, IConvertible
{
}

The only way I can think of doing this is by getting all available enumeration values checking which are set and confirming that only the two provided have been.

Is there another way to solve this problem using some sort of bitwise operation?

Answer 1

Do "or" on all required flags and compare with input - should be equal. Similar to following, with correct loop to compute value on the left:

var onlyTheseFlagsSet = (value[0] | value[1]) == input;

Answer 2

Exclusivity requirement means that

input = values[0] | values[1] | ... | values[values.Length - 1]

So, here is your implementation:

return input.ToInt32(null) == values.Aggregate(0, 
       (total, next) => total | next.ToInt32(null));

Answer 3

This flips the bit of each input value. If only those are set, the resulting value will be zero. Otherwise, it will flip bits to 1 if the value is not set in input which will leave the value non-zero.

public static bool OnlyTheseFlagsSet<T>(this T input, params T[] values) where T : struct, IConvertible
{
    int enumVal = input.ToInt32(null);

    foreach (T itm in values)
    {
        int val = itm.ToInt32(null);
        enumVal = enumVal ^ val;                
    }

    return (enumVal == 0);
}