How do I get the name of a type argument in a generic method?

Question

I have a generic method in my class:

public static void populateSoapBody<TEnum>(Object obj, string[] aMessage) 
   where TEnum : struct,  IComparable, IFormattable, IConvertible

then I use it to populate the class obj from the string array aMessage (as detailed here in my other question) ...

Now, for error logging, I'd like to get the name of the type argument that was passed in for the TEnum type parameter. For example:

private enum DCSSCutomerUpdate_V3
{
       ...
}

so, when I call the method like this:

Common.populateSoapBody<DCSSCustomerUpdate_V3>(wsSoapBody, aMessage);

in that method, I want to be able to get DCSSCustomerUpdate_V3 as a string

And what is the use of `` if you don't use it in any parameters — EZI, Jan 27 '15 at 22:32
@BradleyDotNET: That's the name of the type; I believe the OP wants the name of the actual constant. — Eric Lippert, Jan 27 '15 at 22:33
@EricLippert Can you actually call it as `populateSoapBody()`? That seems like an awful abuse of generics — BradleyDotNET, Jan 27 '15 at 22:34
@BradleyDotNET: No, you can't do that. I think the OP is trying to say that parameter "obj" is a value of type TEnum. The question is confusing. — Eric Lippert, Jan 27 '15 at 22:35
@EZI: I use it to define the members of the class to be populated, and the index of the string array which as the data that needs to go into the class — Our Man in Bananas, Jan 27 '15 at 22:35
@OurManInBananas But you can use it as `populateSoapBody(anotherEnum,null)` so do you think it is correct? — EZI, Jan 27 '15 at 22:36
This is still really confusing. Could you explain *exactly* what name you are talking about, and what `TEnum` has to do with any of this? — BradleyDotNET, Jan 27 '15 at 22:36
What is more interesting to me is why the OP asked the question without trying ToString first. — Eric Lippert, Jan 27 '15 at 22:36
I want the name of the Enumerated constant defined by `TEnum` so when I call the method using `Common.populateSoapBody(wsSoapBody, aMessage);` I can get the string `DCSSCustomerUpdate_V3` — Our Man in Bananas, Jan 27 '15 at 22:39
In this case you should look at the @BradleyDotNET's answer or more specific `typeof(TEnum).Name`. — Hamlet Hakobyan, Jan 27 '15 at 22:45
you said to clarify, but you repeated the same thing. you should specify that you want the name of `TEnum` — Selman Genç, Jan 27 '15 at 22:47

Eric Lippert · Accepted Answer · 2015-01-27T22:46:27.300

12

I want the name of the actual constant.

obj.ToString()

gives you the name of the enumerated element if obj is a boxed instance of an enumerated type. For example:

class P
{
  enum E { ABC } 
  static void Main()
  {
     object obj = E.ABC;
     Console.WriteLine(obj.ToString()); // ABC
  }
}

I want the name of the Enumerated constant that I pass in when calling it. So, defined by TEnum so when I call the method using Common.populateSoapBody<DCSSCustomerUpdate_V3>(wsSoapBody, aMessage); I can get the string DCSSCustomerUpdate_V3

That is not a constant. You will make it much easier on both yourself and the people trying to help you if you use the right names for things.

E.ABC above is a constant. E is a type. In your example TEnum is a type parameter and the type DCSSCustomerUpdate_V3 is a type argument.

Your question is therefore:

I have a generic method M<T>(); how do I get the name of the type argument supplied for type parameter T?

The answer to that is:

void M<T>()
{
    Console.WriteLine(typeof(T).Name);
}

edited Jan 27 '15 at 22:46

answered Jan 27 '15 at 22:37

Eric Lippert

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sorry Eric, I want the name of the Enumerated constant that I pass in when calling it. So, defined by `TEnum` so when I call the method using `Common.populateSoapBody(wsSoapBody, aMessage)`; I can get the string **DCSSCustomerUpdate_V3** – Our Man in Bananas Jan 27 '15 at 22:41
@Eric Lippert: Yes, you are right, I was blind to the fact that it's a Type .. thanks for explaining I have edited my question to give more information – Our Man in Bananas Jan 27 '15 at 22:54
Thank you for your explanation - I guess coming from VB6 and learning c# on the job I haven't really got a decent grounding in types yet... – Our Man in Bananas Jan 28 '15 at 09:26

score 5 · Answer 2 · answered Jan 27 '15 at 22:46

5

To get the name of the type TEnum, just use:

typeof(TEnum).Name

Note that this has nothing to do with the fact that its an enum, and is not a "Enumerated constant", so I think you have some terminology wrong here as well.

answered Jan 27 '15 at 22:46

BradleyDotNET

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it's defined as an Enum in the calling class like this: `private enum DCSSCustomerUpdate_V3 { InstId = 8,` – Our Man in Bananas Jan 27 '15 at 22:47
1

@OurManInBananas That doesn't mean that the code here has **anything** to do with that. See Eric's answer as to the correct terminology here. – BradleyDotNET Jan 27 '15 at 22:48

How do I get the name of a type argument in a generic method?

2 Answers2