My name
is
Jon Skeet

Proper conversion to enum

I have an enum with a bunch of values that looks like this. Notice that I use 0 for "undefined".

public enum MyEnum
{
   Apple = 1,
   Banana = 2,
   Orange = 3,
   Undefined = 0
}

I want to create a conversion method that will receive an int value and return enum but I want to make sure that if a value that is NOT in my enum is received, I return "Undefined". I have the following code but if I pass 47, I want to make sure I get MyEnum.Undefined. How should I modify this code so that any undefined value returns MyEnum.Undefined.

public static MyEnum GetEnum(int value)
{
   var enumValue = MyEnum.Undefined;

   if(value > 0)
      enumValue = (MyEnum)value;

   return enumValue;
}

Just use Enum.IsDefined:

public static MyEnum GetEnum(int value) =>
    Enum.IsDefined(typeof(MyEnum), value) ? (MyEnum) value : MyEnum.Undefined;

Complete example:

using System;

public enum MyEnum
{
    // Moved here as it's more conventional.
    Undefined = 0,
    Apple = 1,
    Banana = 2,
    Orange = 3
}

class Test
{
    public static void Main()
    {
        Console.WriteLine(GetEnum(5)); // Undefined
        Console.WriteLine(GetEnum(0)); // Undefined
        Console.WriteLine(GetEnum(-1)); // Undefined
        Console.WriteLine(GetEnum(3)); // Orange
    }

    public static MyEnum GetEnum(int value) =>
        Enum.IsDefined(typeof(MyEnum), value) ? (MyEnum) value : MyEnum.Undefined;
}

See more on this question at Stackoverflow