Why does Enum.GetValues() return names when using "var"?

Question

Can anyone explain this?

alt text http://www.deviantsart.com/upload/g4knqc.png

using System;  namespace TestEnum2342394834 {     class Program     {         static void Main(string[] args)         {             //with "var"             foreach (var value in Enum.GetValues(typeof(ReportStatus)))             {                 Console.WriteLine(value);             }              //with "int"             foreach (int value in Enum.GetValues(typeof(ReportStatus)))             {                 Console.WriteLine(value);             }          }     }      public enum ReportStatus     {         Assigned = 1,         Analyzed = 2,         Written = 3,         Reviewed = 4,         Finished = 5     } } 

Answer 1

Enum.GetValues is declared as returning Array.
The array that it returns contains the actual values as ReportStatus values.

Therefore, the var keyword becomes object, and the value variable holds (boxed) typed enum values.
The Console.WriteLine call resolves to the overload that takes an object and calls ToString() on the object, which, for enums, returns the name.

When you iterate over an int, the compiler implicitly casts the values to int, and the value variable holds normal (and non-boxed) int values.
Therefore, the Console.WriteLine call resolves to the overload that takes an int and prints it.

If you change int to DateTime (or any other type), it will still compile, but it will throw an InvalidCastException at runtime.

Answer 2

According to the MSDN documentation, the overload of Console.WriteLine that takes an object internally calls ToString on its argument.

When you do foreach (var value in ...), your value variable is typed as object (since, as SLaks points out, Enum.GetValues returns an untyped Array) and so your Console.WriteLine is calling object.ToString which is overriden by System.Enum.ToString. And this method returns the name of the enum.

When you do foreach (int value in ...), you're casting the enum values to int values (instead of object); so Console.WriteLine is calling System.Int32.ToString.