Enums and no field with a value of '0'

Question

I made the following test code:

public enum Test { One = 1, Two = 2 } public class User { public Test Flag { get; set; } } 

What I use like this:

 var user = new User(); var value = typeof(Test).GetField(user.Flag.ToString()); 

The value will be null , as it appears that User.Flag initialized to 0 . Why is this? 0 not a valid value for my enumeration. Shouldn't it be initialized with the first valid value ( 1 )?

Answer 1

Reserves are supported by integral types and behave like them (mostly).

Unfortunately, this means that you can assign any value that is valid for the base type to an enumeration - the check is not performed.

In the case of default initialization, this will be the default value for the base type, which is 0 for integral types.

You can also do this and compile and run:

 var value = (Test)43; 

Perhaps redefine your listing as follows:

 public enum Test { None = 0, One = 1, Two = 2 } 

The Enum class has several convenient methods for working with enumerations - for example, IsDefined , to find out if a variable contains a specific enumeration value.

Answer 2

It is initialized by default to the base type, which is int and default(int) 0 .

Answer 3

By default, the Enum type has an int type by default, and the default value is 0 (you can specify a custom base type, but only a primitive number, for example enum CustomEnum : byte )

1.10 Enumerations, C # Specification:

Each type of enumeration has a corresponding integral type called the base type of the enumeration type. An enumeration type that does not explicitly declare a base type has an int base type. Enumeration types The storage format and the range of possible values ​​are determined by its base type. A set of values ​​that an enumeration type can use, not limited to its enumeration members. In particular, any value of a base enumeration type can be transferred to an enumeration type and is an excellent valid value for this enumeration type.

Answer 4

GetField takes the name of the property name , and you pass the value of the user.Flag

You have to write

 var value = (Test) typeof(Test).GetField("Flag").GetValue(user);