转换为枚举与Enum.ToObject

Question

I recently saw a project that was using this style :

(SomeEnum)Enum.ToObject(typeof(SomeEnum), some int)

instead of this style:

(SomeEnum)some int

Why use the former? Is it just a matter of style?

From MSDN:

This conversion method returns a value of type Object. You can then cast it or convert it to an object of type enumType.

https://msdn.microsoft.com/en-us/library/ksbe1e7h(v=vs.110).aspx

It seems to me that MSDN tells me that I should call ToObject(), and then I can cast. But I'm confused because I know I can cast without calling that method. What is the purpose of ToObject()? What does it accomplish that simple casting does not?

Answer 1

In most cases simple cast is enough.

But sometimes you get type only in runtime. Here comes Enum.ToObject into play. It can be used in cases, when you need dynamically get enum values (or maybe metadata (attributes) attached to enum values). Here is an simple example:

enum Color { Red = 1, Green, Blue }
enum Theme { Dark = 1, Light, NotSure }

public static void Main(string[] args)
{
    var elements = new[]
    {
        new { Value = 1, Type = typeof(Color) },
        new { Value = 2, Type = typeof(Theme) },
        new { Value = 3, Type = typeof(Color) },
        new { Value = 1, Type = typeof(Theme) },
        new { Value = 2, Type = typeof(Color) },
    };

    foreach (var element in elements)
    {
        var enumValue = Enum.ToObject(element.Type, element.Value);
        Console.WriteLine($"{element.Type.Name}({element.Value}) = {enumValue}");
    }
}

Output is:

Color(1) = Red
Theme(2) = Light
Color(3) = Blue
Theme(1) = Dark
Color(2) = Green

More info on enum casting