Trying to do something multiple times

Question

I have this simple function which Tries to get a pages Html, returns null if an exception is thrown

 public static string TryGetPageHtml(string link, System.Net.WebProxy proxy = null)
        {
            System.Net.WebClient client = new System.Net.WebClient() { Encoding = Encoding.UTF8 };
            if (proxy != null)
            {
                client.Proxy = proxy;
            }

            using (client)
            {
                try
                {
                    return client.DownloadString(link);
                }
                catch (Exception ex)
                {
                    return null;
                }
            }

        }

i want to call this function 3 times if it returns null three times that means it faild, so i came up with the following

one way to do that is

        string HTML = null;
        int triesRemaining = 3;
        while (HTML == null && triesRemaining--!=0)
        {
            HTML = TryGetPageHtml(link,getrandomproxy());
        }
        if(HTML == null){//do the handlig}

and another i came up with is

HTML = TryGetPageHtml(link,getrandomproxy())??TryGetPageHtml(link,getrandomproxy())??TryGetPageHtml(link,getrandomproxy());
             if(HTML == null){//do the handlig}

is there a better way and are there built in things in .net that could make this more readable?

no but why you are searching for HTML ??? and why you are getting null?? — The Hungry Dictator, Dec 10 '13 at 03:03
@GrantWinney yes forexample if the proxy was unreachable, then i the getrandomproxy() returns another proxy — FPGA, Dec 10 '13 at 03:06
Duplicate? If not, this should at least give some good ideas... http://stackoverflow.com/q/1563191/945456 — Jeff B, Dec 10 '13 at 03:45

score 3 · Accepted Answer · answered Dec 10 '13 at 03:03

Could do a for loop with a break when it found the html:

        string HTML = null;
        for (int i = 0; i < 3; i++)
        {
            HTML = TryGetPageHtml(link, getrandomproxy());
            if (HTML != null)
                break;
        }

score 1 · Answer 2 · answered Dec 10 '13 at 03:31

Or you could set this up as a recursive function that took the number of attempts as an argument.

public static string TryGetPageHtml(string link, int attempCount = 1,
 System.Net.WebProxy proxy = null, string foundHTML = null)
{
    if(attemptCount == 0 || foundHTML != null)
    {
        return foundHTML;
    }

    if (proxy != null)
    {
        client.Proxy = proxy;
    }

    using (System.Net.WebClient client = new System.Net.WebClient())
    {
        client.Encoding = Encoding.UTF8;

        try
        {
            foundHTML = client.DownloadString(link);
        }
        catch (Exception ex)
        {
            return null; //Remove this if we want to retry on exception
        }
        finally
        {
            return TryGetPageHtml(link, --attemptCount, proxy, foundHTML);
        }
    }
}

score 0 · Answer 3 · answered Dec 10 '13 at 03:28

0

How about this? More readable probably.

var iCount = 0;
string HTML = null;

while (iCount++ < 3 && HTML == null)
{
    HTML = TryGetPageHtml(link, getrandomproxy());
}

answered Dec 10 '13 at 03:28

Adarsh Shah

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Trying to do something multiple times

3 Answers3