Determine the name of a constant based on the value

Question

Is there a way of determining the name of a constant from a given value?

For example, given the following:

public const uint ERR_OK = 0x00000000;

How could one obtain "ERR_OK"?

I have been looking at refection but cant seem to find anything that helps me.

Answer 1

You won't be able to do this since constants are replaced at compilation time with their literal values.

In other words the compiler takes this:

class Foo
{
    uint someField = ERR_OK;
}

and turns it into this:

class Foo
{
    uint someField = 0;
}

Answer 2

I don't think you can do that in a deterministic way. What if there are multiple constants with the same value?

Answer 3

In general, you can't. There could be any number of constants with the same value. If you know the class which declared the constant, you could look for all public static fields and see if there are any with the value 0, but that's all. Then again, that might be good enough for you - is it? If so...

public string FindConstantName<T>(Type containingType, T value)
{
    EqualityComparer<T> comparer = EqualityComparer<T>.Default;

    foreach (FieldInfo field in containingType.GetFields
             (BindingFlags.Static | BindingFlags.Public))
    {
        if (field.FieldType == typeof(T) &&
            comparer.Equals(value, (T) field.GetValue(null)))
        {
            return field.Name; // There could be others, of course...
        }
    }
    return null; // Or throw an exception
}

Answer 4

You may be interested in Enums instead, which can be programmatically converted from name to value and vice versa.

Answer 5

I suggest you use an enum to represent your constant.

Or

string ReturnConstant(uint val)
{
     if(val == 0x00000000)
       return "ERR_OK";
     else
       return null;
}

Answer 6

The easiest way would be to switch to using an enum