C＃-如果if陈述为true，请尝试两次

Question

I have a code parsing a website and adding some values to a list. Sometimes I need to parse the website two times and add the second parsevalues to the same list.

This is some of the code:

public async Task<IEnumerable<Info>>....
{
var values = new List<Info>();
var request = something;
var request_rewritten = rewritten request to run the second time;
......
if request contains something do all the under two times. Both for the request and the rewritten request and add it to result. 
......
var response = await RequestBytes(request);
var results = Encoding.GetEncoding("iso-8859-1").GetString(response.Content);
_fDom = results;

   try
   {
   do something and a lot of code
   ......
   values.Add(result);
   return result
   }
}

If request contains something I need try try a second time. Both for the original request and the rewritten request and add both to the result. Can this be done?

Answer 1

You can follow this pattern. Add an additional parameter to your method indicating retries remaining.

void DoSomething(arg1, arg2, int retriesRemaining = 0)
{
    try
    {
        DoWork();
    }
    catch
    {
        if (retriesRemaining) DoSomething(arg1, arg2, --retriesRemaining);
    }
}

Answer 2

I suppose if you want to avoid writing a method (which is the best answer to your question) you can use a flag:

bool bRunAgain = true;

while (bRunAgain)
{
   // Your logic, check result and see if you need to run it again

   if (your condition to run again == false)
   {
      bRunAgain = false;
   }
}

Answer 3

Here is a common solution. Pass an action to this method and specify retries count

public bool ExecuteWithRetry(Action doWork, int maxTries=1) {
   for(var tryCount=1; tryCount<=maxTries; tryCount++){
      try{
         doWork();
      } catch(Exception ex){
         if(tryCount==MaxTriex){
            Console.WriteLine("Oops, no luck with DoWork()");
            return false;
         }
      }
      return true;
   }
}

so in your method

void Something(){
  ....
  if(ExecuteWithRetry(()=>NotTrustyMethod(), 2)) {
     //success
  } else {
     //fail
  }


}

void NotTrustyMethod(){ ...}

This solution you can use for any case where you need retry option for methods with any type of arguments (or without them)