c# - 无法将类型 'void' 隐式转换为 System.Action

Question

我正在尝试使用输入参数 int 创建 .net 标准委托(delegate) Action。但是我越来越

Cannot implicitly convert type 'void' to System.Action.

我了解到可以将相同的返回类型方法添加到多播委托(delegate)。下面是我的代码。这段代码有什么问题？如果我编写 lambda 表达式，我不会看到编译错误。

static void Main(string[] args)
{
    Action<int> AddBook = AddBookwithId(15); // Here is the error
    AddBook += x => Console.WriteLine("Added book with :{0}" , x ); // No compile error here
    AddBook += AddBookwithISBN(56434);// of course, the same error here too.
}

public static void AddBookwithId(int y)
{
    Console.WriteLine( "Added Book to the shelf with the ID : {0} ", y ); 
}

public static void AddBookwithISBN(int y)
{
    Console.WriteLine("Added Book to the shelf  with the ISBN: {0} ", y + 2);
}

Answer 1

下面的代码编译...当调用 Action 时，预期传递整数。

       Action<int> AddBook = AddBookwithId; // Here is the error
       AddBook += x => Console.WriteLine("Added book with :{0}", x); // No compile error here
       AddBook += AddBookwithISBN;// of course, the same error here too.