Func 和 Action 与不同数量的构造函数参数不一致？

Question

我正在开发一个 twitch 聊天机器人，在我的 Command.cs class 中我遇到了一个奇怪的问题。我有一个采用 Action<string, User, Channel> 的构造函数和一个采用 Func<string, User, Channel, bool> 的构造函数。第一个构造函数应该用 Func 调用第二个构造函数，后者调用 Action 和 return 为真。当我在两个构造函数中使用 7 个参数时，这工作正常，但一旦我添加第 8 个参数，它就停止编译。

我得到的错误是 CS8030 "Anonymous function converted to a void returning delegate cannot return a value." 但在我添加第 8 个参数之前，代码编译正常

这两个片段之间的唯一区别是我添加了一个额外的 description 参数。

之前：

public class Command
{
    public Command(string name, Action<string, User, Channel> action, bool adminOnly = false, bool modOnly = false, bool ownerOnly = false, bool hasUserCooldown = true, TimeSpan? cooldown = null, bool allowOtherCommands = false)
        : this(name, (m, u, c) => { action(m, u, c); return true; }, adminOnly, modOnly, ownerOnly, hasUserCooldown, cooldown)
    {

    }

    public Command(string name, Func<string, User, Channel, bool> action, bool adminOnly = false, bool modOnly = false, bool ownerOnly = false, bool hasUserCooldown = true, TimeSpan? cooldown = null, bool allowOtherCommands = false)
    {

    }
}

public class User { }
public class Channel { }

之后：

public class Command
{
    public Command(string name, Action<string, User, Channel> action, bool adminOnly = false, bool modOnly = false, bool ownerOnly = false, bool hasUserCooldown = true, TimeSpan? cooldown = null, bool allowOtherCommands = false, string description = null)
        : this(name, (m, u, c) => { action(m, u, c); return true; }, adminOnly, modOnly, ownerOnly, hasUserCooldown, cooldown, description)
    {

    }

    public Command(string name, Func<string, User, Channel, bool> action, bool adminOnly = false, bool modOnly = false, bool ownerOnly = false, bool hasUserCooldown = true, TimeSpan? cooldown = null, bool allowOtherCommands = false, string description = null)
    {

    }
}

public class User { }
public class Channel { }

非常感谢。

Answer 1

在这两个版本中，您忘记将 allowOtherCommands 可选参数传递给第二种方法。虽然在第一种方法中它只是编译器无法捕获的逻辑错误，但在第二种情况下 description 参数导致编译器将调用映射到期望 Action 的同一构造函数，因此错误。

只需传递所有可选参数，问题就会解决：

public Command(string name, Action<string, User, Channel> action, 
    bool adminOnly = false, bool modOnly = false, bool ownerOnly = false, bool hasUserCooldown = true, 
    TimeSpan? cooldown = null, bool allowOtherCommands = false, string description = null)
    : this(name, (m, u, c) => { action(m, u, c); return true; }, 
        adminOnly, modOnly, ownerOnly, hasUserCooldown, 
        cooldown, allowOtherCommands, description)
{

}

Func 和 Action 与不同数量的构造函数参数不一致？

Inconsistency between Func and Action with different amount of constructor parameters?

c#

action

anonymous-function

func