Cannot write to a closed TextWriter

Question

I am trying to write text to my txt file. After the first write the application crash with error

Cannot write to a closed TextWriter

My list contains links that the browser opens and I want to save all of them in txt file (like a log).

My code:

FileStream fs = new FileStream(
                    "c:\\linksLog.txt", FileMode.Append, FileAccess.Write);
StreamWriter sw = new StreamWriter(fs);

for (int i = 0; i < linksList.Count; i++)
{
    try
    {
        System.Diagnostics.Process.Start(browserType, linksList[i]);
    }
    catch (Exception) { }

    using (sw)
    {
        sw.WriteLine(linksList[i]);
        sw.Close();
    }

    Thread.Sleep((int)delayTime);

    if (!cbNewtab.Checked)
    {
        try
        {
            foreach (Process process in Process.GetProcesses())
            {
                if (process.ProcessName == getProcesses)
                {
                    process.Kill();
                }
            }
        }
        catch (Exception) { }
    }
}

Don't close the StreamWriter (sw) until you are done using it. — Davin Tryon, Mar 18 '12 at 15:22

Ry- · Accepted Answer · 2019-12-17T06:22:30.157

You're in a for loop, but you close and dispose of your StreamWriter on the first iteration:

using (sw)
{
    sw.WriteLine(linksList[i]);
    sw.Close();
}

Instead, remove that block, and wrap everything in one using block:

using (var sw = new StreamWriter(@"C:\linksLog.txt", true)) {
    foreach (var link in linksList) {
        try {
            Process.Start(browserType, list);                        
        } catch (Exception) {}

        sw.WriteLine(link);

        Thread.Sleep((int)delayTime);

        if (!cbNewtab.Checked) {
            var processes = Process.GetProcessesByName(getProcesses);

            foreach (var process in processes) {
                try {
                    process.Kill();
                } catch (Exception) {}
            }
        }
    }
}

score 2 · Answer 2 · answered Mar 18 '12 at 15:20

The problem is that you are closing you Stream in the loop, should done only after...

FileStream fs = new FileStream("c:\\linksLog.txt", FileMode.Append, FileAccess.Write);
StreamWriter sw = new StreamWriter(fs);

    for (int i = 0; i < linksList.Count; i++)
    {
        try
        {
            System.Diagnostics.Process.Start(browserType, linksList[i]);                        
        }
        catch (Exception)
        {

        }
        // Removed the using blocks that closes the stream and placed at the end of loop
        sw.WriteLine(linksList[i]);

        Thread.Sleep((int)delayTime);

        if (!cbNewtab.Checked)
        {
            try
            {
                foreach (Process process in Process.GetProcesses())
                {
                    if (process.ProcessName == getProcesses)
                    {
                        process.Kill();
                    }
                }
            }
            catch (Exception)
            { }
        }
    }

    sw.Close();

score 2 · Answer 3 · answered Mar 18 '12 at 15:21

The line

using (sw)

closes/disposes your StreamWriter.

Since you are looping, you dispose an already disposed StreamWriter.

Better to close the StreamWriter outside the loop, after all write operations are finished.

In addition, catching exceptions and ignoring the caught exception is almost always a bad idea. If you can't handle an exception, do not catch it.

score 1 · Answer 4 · answered Mar 18 '12 at 15:21

1

That's because you are, indeed, closing your stream in the middle of the loop. You have the using (sw) block in the middle, which will work fine in the first run through the for loop, and then crash. To fix it, just drop the sw.Close() call, and move the using to be outside the for loop:

answered Mar 18 '12 at 15:21

Avner Shahar-Kashtan

14,492
3
37
63

but what if the app crash in the middle ? – user1269592 Mar 18 '12 at 15:26
You can call `sw.Flush()` if you want the data to be written to disk in every iteration, though in general, the `using` call translates to a `try {} catch {} finally { sw.Dispose();}` call, so even if you throw an exception, the stream is closed properly. – Avner Shahar-Kashtan Mar 18 '12 at 15:46
if i want to use using, i need to write close() ? where to put using in my code ? – user1269592 Mar 18 '12 at 17:25
You don't need to call `Close()` explicitly. The `using` takes care of that. – Avner Shahar-Kashtan Mar 18 '12 at 17:34

score 0 · Answer 5 · edited Jul 11 '12 at 12:38

0

Dont write the sw.Close() in your code because if the file is closed the code cannot read the file.

edited Jul 11 '12 at 12:38

Fahim Parkar

30,974
45
160
276

answered Mar 18 '12 at 15:25

Arshiya

45
8

there is way that i can ongoing see all my link in the file ? i mean in the middle of the process while i am still in the for statement – user1269592 Mar 18 '12 at 15:51

Cannot write to a closed TextWriter

5 Answers5