ReSharper 警告:“泛型类型中的静态字段" [英] ReSharper warns: "Static field in generic type"

问题描述

public class EnumRouteConstraint<T> : IRouteConstraint
    where T : struct
{
    private static readonly Lazy<HashSet<string>> _enumNames; // <--

    static EnumRouteConstraint()
    {
        if (!typeof(T).IsEnum)
        {
            throw new ArgumentException(
                Resources.Error.EnumRouteConstraint.FormatWith(typeof(T).FullName));
        }

        string[] names = Enum.GetNames(typeof(T));
        _enumNames = new Lazy<HashSet<string>>(() => new HashSet<string>
        (
            names.Select(name => name), StringComparer.InvariantCultureIgnoreCase
        ));
    }

    public bool Match(HttpContextBase httpContext, Route route, 
                        string parameterName, RouteValueDictionary values, 
                        RouteDirection routeDirection)
    {
        bool match = _enumNames.Value.Contains(values[parameterName].ToString());
        return match;
    }
}

这是错误的吗?我假设这实际上有一个 static readonly 字段，用于我碰巧遇到的每个可能的 EnumRouteConstraint.

Is this wrong? I would assume that this actually has a static readonly field for each of the possible EnumRouteConstraint<T> that I happen to instance.

推荐答案

在泛型类型中有一个静态字段是可以的，只要你知道每个类型参数组合你真的会得到一个字段.我的猜测是 R# 只是警告你，以防你不知道这一点.

It's fine to have a static field in a generic type, so long as you know that you'll really get one field per combination of type arguments. My guess is that R# is just warning you in case you weren't aware of that.

这是一个例子:

using System;

public class Generic<T>
{
    // Of course we wouldn't normally have public fields, but...
    public static int Foo;
}

public class Test
{
    public static void Main()
    {
        Generic<string>.Foo = 20;
        Generic<object>.Foo = 10;
        Console.WriteLine(Generic<string>.Foo); // 20
    }
}

如您所见，Generic.Foo 与 Generic