С#。错误 "Expected method with different signature"。但显示相同的签名

Question

我在 Program.cs

中有事件处理程序方法 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 class 库，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？这两种方法具有相同的签名。为什么当我将方法放入 class 库时程序会中断？

在 Program.cs:

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

Answer 1

您的错误是由于 CriticalSituationGacEventArgs 跨程序集的多个定义而发生的。为了说明一点，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（我们称之为 B）中我们有：

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 处出现错误。为了更深入地理解这一点，我们可以更明确地将其定义为：

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

这试图将 A.CriticalSituationGacEventArgs 传递给期望 B.CriticalSituationGacEventArgs 的参数，这给出了一个错误：

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，有几种选择可以解决此问题：

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。那么A和B在定义事件（在A中）和处理事件（在B中）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