为什么使用“var”时Enum.GetValues（）返回名称？ [英] Why does Enum.GetValues() return names when using "var"?

问题描述

任何人都可以解释这一点吗？

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
    }
}

推荐答案

Enum.GetValues 被声明为返回 。

它返回的数组包含实际值为 ReportStatus 值。

因此， var 关键字变为对象， / code>变量保存（boxed）键入的枚举值。

Console.WriteLine 调用解析为需要对象并调用对象上的 ToString（），枚举枚举返回名称。

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.

当您迭代 int 时，编译器会将值转换为 int ， 值变量保持正常（和非盒装） int 值。

因此， Console.WriteLine 调用解析到需要 int 并重新打印的重载。

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.

如果更改 int to DateTime （或任何其他类型），它仍然会编译，但它会抛出一个 InvalidCastException 在运行时。

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

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