HtmlTextWriter doesn't flush upon disposal?

Question

I need to write some text with style (like color, fonts) so I decided to use html. I found that HtmlTextWriter is a class used for writing html file. However, I found that I must manually close or flush it otherwise nothing is written to the file. Why is it? (using statement should dispose it when the block is finished)

        using (HtmlTextWriter htmlWriter = new HtmlTextWriter(new StreamWriter(
            Path.Combine(EmotionWordCounts.FileLocations.InputDirectory.FullName, fileName),
            false, Encoding.UTF8)))
        {
            try
            {

                htmlWriter.WriteFullBeginTag("html");
                htmlWriter.WriteLine();
                htmlWriter.Indent++;

                htmlWriter.WriteFullBeginTag("body");
                htmlWriter.WriteLine();
                htmlWriter.Indent++;

                // write something using WriteFullBeginTag and WriteEndTag
                // ...

            } //try
            finally
            {
                htmlWriter.Indent--;
                htmlWriter.WriteEndTag("body");
                htmlWriter.WriteLine();

                htmlWriter.Indent--;
                htmlWriter.WriteEndTag("html");
                htmlWriter.Close(); // without this, the writer doesn't flush
            }
        } //using htmlwriter

Thanks in advance.

Eamon Nerbonne · Accepted Answer · 2011-07-06T12:20:09.543

This is a bug in HtmlTextWriter. You should make a self-contained test case and report it using Microsoft Connect. It seems that Close and Dispose behave differently, which isn't documented and is extremely unusual. I also can't find any documentation on MSDN stating whether the HtmlTextWriter takes ownership of the underlying textwriter or not; i.e. will it dispose the underlying textwriter or must you?

Edit 2: The MSDN page on HtmlTextWriter states that it inherits (as opposed to overrides) the virtual Dispose(bool) method. This means the current implementation clearly cannot clean up with a using block. As a workaround, try this:

using(var writer = ...make TextWriter...) 
using(var htmlWriter = new HtmlTextWriter(writer)) {

    //use htmlWriter here...

} //this should flush the underlying writer AND the HtmlTextWriter

// although there's currently no need to dispose HtmlTextWriter since
// that doesn't do anything; it's possibly better to do so anyhow in 
// case the implementation gets fixed

Incidentally, new StreamWriter(XYZ, false, Encoding.UTF8) is equivalent to new StreamWriter(XYZ). StreamWriter creates rather than appends by default, and it uses UTF8 without BOM by default as well.

Good luck - and don't forget to report the bug!

Thanks a lot. It helps a lot. I just got some basic ideas about how to use it; I didn't write html before. But I am not familiar with the reporting thing. Maybe you should report this bug. (Or is it a feature?) — LLS, Jul 06 '11 at 21:49

score 0 · Answer 2 · answered Jul 06 '11 at 11:52

0

You do not need to have the try{} Finally {} block within the using statement as this will dispose of the object for you.

answered Jul 06 '11 at 11:52

Matt Seymour

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Thanks for your suggestion. I think for html document it may not be necessary. – LLS Jul 06 '11 at 21:45

score 0 · Answer 3 · answered Jul 06 '11 at 11:59

0

I suspect the reason is that HtmlTextWriter does not provide an override for TextWriter's protected virtual void Dispose( bool disposing ) method to call Close() so, you're right, you'll need to do this yourself - TextWriter's implementation is empty. As aspect has pointed out, you don't need the try finally block within the using statement though. As Eamon Nerbonne has pointed out, this is surely a framework bug.

answered Jul 06 '11 at 11:59

Bart Read

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Thanks. I copied some code from a XMLTextWriter program, and I think it's a good idea to always WriteEndDocument. But it's not a big problem here I believe. – LLS Jul 06 '11 at 21:43

HtmlTextWriter doesn't flush upon disposal?

3 Answers3