【问题标题】：С#. Error "Expected method with different signature". But show same signatureС#。错误“具有不同签名的预期方法”。但显示相同的签名
【发布时间】：2021-04-18 13:40:15
【问题描述】：

我在Program.cs 中有事件处理方法c_CriticalSituationHappened

void c_CriticalSituationHappened(object sender, CriticalSituationGacEventArgs e)
{
    if (e.TypeDisrepair != TypeDisrepairGac.None)
        {
            start_time = DateTime.UtcNow;
            typeDisrepair = e.TypeDisrepair;
            WriteLine("Crit sit time: " + start_time);
            isStarted = true;
         }
}

如果我将它移动到类库中，我会导入它。

public class CorrectBehaviorCheck
{
    public void CriticalSituationHappened1(object sender, CriticalSituationGacEventArgs e)
        {
            if (e.TypeDisrepair != TypeDisrepairGac.None)
            {
                criticalSituationStartTime = DateTime.Now;
                TypeDisrepair = e.TypeDisrepair;
                Console.WriteLine("111");
                isStarted = true;
            }
        }
}

签名保持完全相同。但是如果尝试

using cbc = mymodule.CorrectBehaviorCheck;
class Program{
static void Main(string[] args){
cbc a = new cbc();
CriticalSituationHappened += a.CriticalSituationHappened1;
}
}

代替

class Program{
static void Main(string[] args){
CriticalSituationHappened += c_CriticalSituationHappened;
}
}

我有一个错误Expected a method with 'void CriticalSituationHappened1(object?, CriticalSituationGacEventArgs)' signature 我做错了什么？两种方法具有相同的签名。为什么将方法放入类库时程序会中断？

在 Program.cs 中：

protected virtual void OnCriticalSituationHappened(CriticalSituationGacEventArgs e)
        {
            EventHandler<CriticalSituationGacEventArgs> handler = CriticalSituationHappened;
            if (handler != null)
            {
                handler(this, e);
            }
        }
public static event EventHandler<CriticalSituationGacEventArgs> CriticalSituationHappened;

【问题讨论】：

您能说明CriticalSituationHappened 是如何与任何代表一起定义的吗？
最后添加
CriticalSituationGacEventArgs 定义在哪个程序集中？你有多个CriticalSituationGacEventArgs 的定义吗？
在 Program.cs 的项目中有一个定义，在导入的模块中有一个定义。（代码相同） public class CriticalSituationGacEventArgs : EventArgs { public string Message {get;放;};公共类型DisrepairGac {get;放;}}。 TypeDisrepairGac 是枚举列表

标签： c# events event-handling delegates class-library

【解决方案1】：

您的错误是由于在程序集中对 CriticalSituationGacEventArgs 的多个定义而发生的。为了说明一下，在主程序集中（我们称之为A）我们有：

namespace A
{
    using cbc = B.CorrectBehaviorCheck;

    public class CriticalSituationGacEventArgs : EventArgs
    {
        public string Message { get; set; }
    }   

    public class Program
    {
        public static event EventHandler<A.CriticalSituationGacEventArgs> CriticalSituationHappened;

        public static void Main(string[] args)
        {
            cbc a = new cbc();
            CriticalSituationHappened += a.CriticalSituationHappened1;
            CriticalSituationHappened(null, new A.CriticalSituationGacEventArgs { Message = "Hello!" });
        }
    }
}

然后在外部程序集中（我们称之为B）我们有：

namespace B
{
    public class CriticalSituationGacEventArgs : EventArgs
    {
        public string Message { get; set; }
    }
    
    public class CorrectBehaviorCheck
    {
        public void CriticalSituationHappened1(object sender, B.CriticalSituationGacEventArgs e)
        {
            Console.WriteLine("Listening in CorrectBehaviorCheck.CriticalSituationHappened1: " + e.Message);
        }
    }
}

这会导致CriticalSituationHappened += a.CriticalSituationHappened1 出现错误。为了进一步理解这一点，我们可以更明确地将其定义为：

CriticalSituationHappened += (object sender, A.CriticalSituationGacEventArgs e) => a.CriticalSituationHappened1(sender, e);

这是试图将A.CriticalSituationGacEventArgs 传递给期望B.CriticalSituationGacEventArgs 的参数，这会产生以下错误：

CS1503  Argument 2: cannot convert from 'A.CriticalSituationGacEventArgs' to 'B.CriticalSituationGacEventArgs'

因为编译器无法知道如何从一种类型转换为另一种类型。鉴于您的情况，有几个选项可以解决此问题：

1。手动转换事件参数

    CriticalSituationHappened += (sender, e) => 
        a.CriticalSituationHappened1(sender, new B.CriticalSituationGacEventArgs 
                                     { 
                                         Message = e.Message,
                                         // set other properties
                                     });

2。在共享程序集中定义一次事件参数

创建一个新项目（例如MyEventArgs）并在该项目中定义一次CriticalSituationGacEventArgs。然后A 和B 在定义事件（A）和处理事件（B）时都可以引用MyEventArgs.CriticalSituationGacEventArgs。这也避免了在A 或B 中定义单一类型的循环依赖。

【讨论】：