WebClient is not thread-safe! - 未名空间MITBBS历史存档

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WebClient is not thread-safe!

WebClient is not thread-safe!# DotNet - 窗口里的风景

c*t2010-08-05 07:08

1 楼

Easy to test:
var links = new ConcurrentQueue(); //and populate with links
Parallel.For(0, link.Count, delegate(int i){
string url;
if( links.TryDeQueue(out url) )
{ Download(url); }
});
...
private void Download(string url)
{
using(WebClient wc = new WebClient())
{
wc.DownloadFile(url, somefilename);
}
}

a92010-08-05 07:08

2 楼

这叫异步执行吧？

【在 c**t 的大作中提到】

: Easy to test:
: var links = new ConcurrentQueue(); //and populate with links
: Parallel.For(0, link.Count, delegate(int i){
: string url;
: if( links.TryDeQueue(out url) )
: { Download(url); }
: });
: ...
: private void Download(string url)
: {

c*d2010-08-05 07:08

3 楼

This is not thread safety. And what issue does WebClient have?

c*t2010-08-05 07:08

4 楼

Only two links were downloaded, app doesn't stop, doesn't download more
links either.

【在 c**d 的大作中提到】

: This is not thread safety. And what issue does WebClient have?

d*d2010-08-05 07:08

5 楼

you create one instace of wc per task, wc doesn't need to be thread-safe.

【在 c**t 的大作中提到】

: Only two links were downloaded, app doesn't stop, doesn't download more
: links either.

c*t2010-08-05 07:08

6 楼

read my code, each task has its own wc (using)

【在 d****d 的大作中提到】

: you create one instace of wc per task, wc doesn't need to be thread-safe.

v*n2010-08-05 07:08

7 楼

how many cpu's (cores) in your machine? It is possible that TPL only
schedules
two threads

【在 c**t 的大作中提到】

: Only two links were downloaded, app doesn't stop, doesn't download more
: links either.

d*d2010-08-05 07:08

8 楼

that's what I meant. wc doesn't need to be thread-safe if you write code
like
this. If it doesn't work, it has nothing to do with wc's thread-safety.

【在 c**t 的大作中提到】

: read my code, each task has its own wc (using)

d*d2010-08-05 07:08

9 楼

I just wrote a test app. I have no problem downloading multiple urls at all.
At peak I have 6 downloading simultaneously.
Something else is wrong in your project. But as I said, it shouldn't have
anything to do with wc's thread safety.

【在 d****d 的大作中提到】

: that's what I meant. wc doesn't need to be thread-safe if you write code
: like
: this. If it doesn't work, it has nothing to do with wc's thread-safety.

s*w2010-08-05 07:08

10 楼

I also tested the above code,
multiple files are downloaded,
wc.DownloadFile(url, filename); the second parameter is the filename you are
going to download to. For each thread, they should have their own file
names.

【在 c**t 的大作中提到】

: Only two links were downloaded, app doesn't stop, doesn't download more
: links either.