Perform Command For List of commands without using IF Statement C#

问题

I have a TcpListener Listening on a NetworkStream to perform a command examples. "Copy, Move, Delete, ...."

switch(command)
{
   case "copy":
   // do copy
   break;
   case "delete":
   // do delete
   break;
   case "move":
   // do move
   break;
   .......................................
}

i have implemented it using switch - case and if statement but when it comes to maintenance or adding a new command, specially when the commands list goes beyond 100 commands it becomes very hard and tedious, so is there a way to do this efficiently, i have tried searching on Google but i can't seem to get the jargon of it correctly
Any help :) Yaser

回答1:

You're looking for Command Pattern. You'll have to create an interface ICommand and implementation of that interface one per command.

For example: CopyCommand, DeleteCommand, MoveCommand etc.

Then you need a factory method which creates instance of respective ICommand based on the string provided.

Finally you'll call ICommand.Execute. That makes it readable, maintainable, clean and so on..

Your code will become

ICommand command = commandFactory.Create(commandString);
command.Execute();

Where commandFactory is an instance of "Factory" which will create instance of appropriate ICommand.

Your Factory class could be implemented using a huge switch case or Dictionary<string, Func<ICommand>> if you prefer.

回答2:

As @Zohar Peled has already mentioned Dictionary is a really cheap solution for this problem, not so elegant, but really cheap:

        //Initialize command lists
        Dictionary<string, Action> commands = new Dictionary<string, Action>();

        commands.Add("move", DoMyMove);
        commands.Add("add", ()=> Console.WriteLine(""));
        commands.Add("remove", DoMyRemove);
        commands.Add("close", DoMyClose);

delegate

        private void DoMyMove()
        {
             // TODO
        }

Usage:

        commands[command].Invoke();

It's extendable easly and clear for basic developers...

回答3:

One option is to define a Dictionary<string,action> on the class level that will hold the name of the command and an action delegate to the actual method that needs to be performed. Then in your main method you don't need to use a switch, simply get the action delegate from the dictionary using the dictionary's TryGetValue Method and if it returns true simply invoke the action delegate.

来源：https://stackoverflow.com/questions/30104924/perform-command-for-list-of-commands-without-using-if-statement-c-sharp

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