Question

所以这是代码，

public void DoSomething<T>(string key, Action<T> callback)
{
    Type typeParameterType = typeof(T);

    if (typeParameterType.Equals(typeof(string)))
    {
        callback("my string response");
    }
    if (typeParameterType.Equals(typeof(int)))
    {
        callback(1); // my int response
    }
    // etc...
}

然而，我遇到了错误......我是所有C＃泛型和委托人的新手。

我得到的错误是，

Error   1   Delegate 'System.Action<T>' has some invalid arguments
Error   2   Argument 1: cannot convert from 'string' to 'T'

对我而言，创造美观实用的方法非常重要。

所以我喜欢像这样实现上面的例子，

int total = 0;
DoSomething<int>("doesn't matter", x => {
    total = 10 + x; // i can do this because x is an INT!!! (:
});

string message = "This message is almost ";
DoSomething<int>("doesn't matter", x => {
    message = "finished!!!"; // i can do this because x is an STRING!!! (:
});

但是我被困了......请帮忙！

=============================================== ================================

正如dasblinkenlight指出的那样，

重载是最干净，编译器最友好的方法......我的API现在看起来像，

DoSomething("doesn't matter", new Action<string>(x => {
    message = "finished!!!"; // i can do this because x is an STRING!!! (:
}));

支付的价格较低且易于理解。

感谢您的回答（：

=============================================== ================================

做一些更多的研究，我可以通过以下方式来清理它;

DoSomething("doesn't matter", (string x) => {
    message = "finished!!!"; // i can do this because x is an STRING!!! (:
});

请注意：（字符串x）

现在编译器知道了！很酷吧？

Answer 1

int和string等特定类型无法转换为T，但object可以转换为if (typeParameterType.Equals(typeof(string))) { callback((T)((object)"my string response")); } if (typeParameterType.Equals(typeof(int))) { callback((T)((object)1)); // my int response }。这应该有效：

public void DoSomething(string key, Action<int> callback) {
    callback(1);
}
public void DoSomething(string key, Action<string> callback) {
    callback("my string response");
}

然而，首先你需要这样做有点奇怪：不是通过泛型跳过箍，你可以用多种方法更优雅地处理问题：

DoSomething("hello", new Action<int>(x => Console.WriteLine("int: {0}", x)));
DoSomething("world", new Action<string>(x => Console.WriteLine("str: {0}", x)));

现在你可以这样调用这些方法：

DoSomething("hello", (int x) => Console.WriteLine("int: {0}", x));
DoSomething("world", (string x) => Console.WriteLine("str: {0}", x));

或者像这样：

{{1}}

Answer 2

您可以查看回调类型：

public void DoSomething<T>(string key, Action<T> callback)
{
    var action1 = callback as Action<string>;
    if (action1 != null)
    {
        action1("my string response");
        return;
    }

    var action2 = callback as Action<int>;
    if (action2 != null)
    {
        action2(1); // my int response
        return;
    }
    // etc...
}

检查Action委托回调中的泛型类型

2 个答案: