Is there a difference when converting an enum to a string between Convert.ToString() vs .ToString()?

Question

Something amazed me with Enum String Conversion

If I do:

(Edit: This assertion is contested - it is true only if an enum variable instance has an invalid value)

Convert.ToString(MyEnum.MyEnumValue); // Returns Integer Representation

Whereas if I do

MyEnum.MyEnumValue.ToString(); // Returns `MyEnumValue`

Why is this behaviour or am I missing something?

@Icepickle: Does it Matter? Any Enum (default it takes base as Integer) which you create would suffice your requirement. — Nikhil Agrawal, Jul 28 '15 at 07:51
There is nothing wrong with the output. As you already stated. The first is a conversion and the second is an string representation of the object. — ckruczek, Jul 28 '15 at 07:52
Please write a compilable repro, because when I try this, the behaviour you describe does NOT happen. In both cases, it returns `MyEnumValue` and NOT the integer representation. — Matthew Watson, Jul 28 '15 at 07:54
@NikhilAgrawal: because with my program, i also do not get your described behavior :D — Icepickle, Jul 28 '15 at 07:55
`ToString` for object calss. but `Convert.ToString` is for `Convert` class. they have different implementations. — M.kazem Akhgary, Jul 28 '15 at 07:58
@M.kazemAkhgary no, basically they are the same. See the [reference source](http://referencesource.microsoft.com/#mscorlib/system/convert.cs,1801). — Patrick Hofman, Jul 28 '15 at 07:59
@M.kazemAkhgary sure you don't cast it to an `int` along the way? — Patrick Hofman, Jul 28 '15 at 08:02
ofc if you cast it to int it will return the number. but no i didnt cast to int. they both return enum value not int. @PatrickHofman — M.kazem Akhgary, Jul 28 '15 at 08:04

Anton · Accepted Answer · 2015-07-28T08:12:50.290

2

I checked code that should be run for both cases. For Enum.ToString:

public override string ToString()
{
    return Enum.InternalFormat((RuntimeType)base.GetType(), this.GetValue());
}
private static string InternalFormat(RuntimeType eT, object value)
{
    if (eT.IsDefined(typeof(FlagsAttribute), false))
    {
        return Enum.InternalFlagsFormat(eT, value);
    }
    string name = Enum.GetName(eT, value);
    if (name == null)
    {
        return value.ToString();
    }
    return name;
}

For Convert.ToString:

this.GetType().ToString();

So, it should work in a same way for both cases. Please provide your code. Here is sample from my side.

edited Jul 28 '15 at 08:12

answered Jul 28 '15 at 08:07

Anton

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Please delete your answer as I want to delete the question. Also this should be a comment. – Nikhil Agrawal Jul 28 '15 at 09:03
@NikhilAgrawal you can delete if there is a non-positive answer scoring, right? – Patrick Hofman Jul 28 '15 at 09:11
@PatrickHofman: Deleting will not happen if there is an answer. Scoring does not matter. – Nikhil Agrawal Jul 28 '15 at 09:18
1

@NikhilAgrawal Beyond 20K it doesn't matter. I can only vote to delete the question if it has a negative score, just like you. (not saying I would vote, just that I can vote) – Patrick Hofman Jul 28 '15 at 09:20

score 0 · Answer 2 · answered Jul 05 '17 at 05:44

As per Anton's answer, the behaviour of Convert.ToString and .ToString() are on an enum is identical.

I believe what may have happened is that you assigned the enum variable an integral value which is out of range of the enumeration. Since enums are internally represented as integral types, the backing type will generally have a much wider range than the enum states that have been defined for it.

Corruption of enum values can occur quite easily, for example during casting, during a deserialization step, or when using enum parsing methods.

As a result, you should always validate that the enum is valid before trusting it in the rest of your system, e.g. through Enum.IsDefined, although you'll need to do further work if you are using FlagsAttribute

enum MyEnum
{
   Value1 = 1,
   Value2 = 2
};

void Main()
{
    // Literal
    Console.WriteLine(Convert.ToString(MyEnum.Value1)); // Value1
    Console.WriteLine(MyEnum.Value1.ToString()); // Value1

    // Variable
    MyEnum myEnum = MyEnum.Value2;
    Console.WriteLine(Convert.ToString(myEnum)); // Value2
    Console.WriteLine(myEnum.ToString());  // Value2

    // Invalid
    MyEnum badEnum = (MyEnum)123;
    Console.WriteLine(Convert.ToString(badEnum)); // 123
    Console.WriteLine(badEnum.ToString()); // 123
}

Is there a difference when converting an enum to a string between Convert.ToString() vs .ToString()?

2 Answers2