How is the usage of begininvoke in C#?

In C#, BeginInvoke is a member of the delegate type used for asynchronously calling a delegate. It is used like this:

1. First, create a delegate instance specifying the method to be called.
2. Use the BeginInvoke method of a delegate instance to start an asynchronous call. This method takes the method arguments to be invoked and a callback function.
3. In the callback function, you can access the results and status of the asynchronous call.

Here is an example code using BeginInvoke:

public class Example
{
    public delegate void MyDelegate(string message);

    public void PrintMessage(string message)
    {
        Console.WriteLine(message);
    }

    public void StartAsync()
    {
        MyDelegate myDelegate = new MyDelegate(PrintMessage);

        myDelegate.BeginInvoke("Hello, World!", PrintCompleted, null);
    }

    public void PrintCompleted(IAsyncResult result)
    {
        // 处理异步调用的结果
        MyDelegate myDelegate = (MyDelegate)((AsyncResult)result).AsyncDelegate;
        myDelegate.EndInvoke(result);
    }
}

public class Program
{
    public static void Main()
    {
        Example example = new Example();
        example.StartAsync();

        // 等待异步调用完成
        Console.ReadLine();
    }
}

In the example above, a delegate type named MyDelegate, which takes a string parameter, is first defined. Then a PrintMessage method is defined to print a message. In the StartAsync method, a MyDelegate delegate instance is created and the PrintMessage method is asynchronously called using the BeginInvoke method. The PrintCompleted callback function can handle the result of the asynchronous call. Finally, in the Main method, an Example instance is created and the StartAsync method is called, followed by waiting for the asynchronous call to complete using the Console.ReadLine method.

Note: when using the BeginInvoke method, it is necessary to manually call the EndInvoke method to end the asynchronous call in order to ensure proper resource release.