CODEWITHSUNDEEP
c#webclient
Joe Martiniello
Joe Martiniello

Reputation: 323

C# WebClient multiple execution

I have a problem with WebClient.

Simple I check file missed in one folder. If I don't have this file, with WebClient I navigate to web page and send a value to execute a query and store the value in the database.

My problem:

I have a List of 1500 Elements for example. But after first element the for loop is stopped (maybe) or doesn't navigate again.

My code:

List<string> fileneed = new List<string>();

In the Thread

//Distinct
            fileneed = fileneed.Distinct().ToList<string>();

            for (int i = 0; i < fileneed.Count; i++)
            {
                if (fileneed[i].Contains("."))
                {
                    w = new WebClient();
                    w.OpenRead("http://mywebsite.org/collab/files.php?act=need&user=" + Properties.Settings.Default.user + "&file=" + fileneed[i]);
                    fileneed.RemoveAt(i);

                }
            }

After execution of the thread, I go to my PhpMyAdmin and I see only one file. Other files in the list don't show or are present or with a strange problem, my code execute one time the loop.

Upvotes: 0

Views: 335

Answers (3)

Martin Brown
Martin Brown

Reputation: 25320

There are a few things wrong with the example code:

1st: Because it is removing items from the fileneed list at the same point it is reading from the list it is going to skip files in the list. This is because when you remove an item, the index of all the following items is made one smaller. We can get around this by iterating over the list from the end to the start.

2nd: Though the code is reading a file from the server, it is not doing anything with the file to write it out to disk. As such the file will simply be lost. This can be fixed by opening a file stream and copying to it.

3rd: WebClient and the Stream returned from OpenRead need to be Disposed. Otherwise the resources they use will not be cleaned up and your program will become a memory/connection hog. This is fixed by using the using statement.

With these three fixes the resulting code looks like this:

fileneed = fileneed.Distinct().ToList<string>();

for (int i = fileneed.Count - 1; i >= 0; i--)
{
    if (fileneed[i].Contains("."))
    {
        using (var w = new WebClient())
        using (var webFile = w.OpenRead("http://mywebsite.org/collab/files.php?act=need&user=" + Properties.Settings.Default.user + "&file=" + fileneed[i]))
        using (var diskFile = File.OpenWrite(fileneed[i]))
        {
            webFile.CopyTo(diskFile);
        }
        fileneed.RemoveAt(i);
    }
}

Upvotes: 2

Emre Kabaoglu
Emre Kabaoglu

Reputation: 13146

http://mywebsite.org/collab/files.php

I don't know this page what exactly do but you should remove this line;

fileneed.RemoveAt(i);

Every iterate, you are removing the element and Count changes. If you want to remove processed items, you could store in another list and except from original string list.

Upvotes: 0

Neil
Neil

Reputation: 11889

You are opening a 'connection' to that file, but you aren't reading it or storing it anyway. You need to create a new file, and read from the remote stream and write to the local file stream:

using(var myFile = File.OpenWrite(fileneed[i]))
{
   w.CopyTo(myFile);    
}

See this page for details

Upvotes: 0

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