XML, Sockets, Streams and a headache

owain · September 6th, 2004, 10:01 AM

I am very new to VB.NET (I started learning it about 2 weeks ago) however I have several years of experience in VB5 and 6 so I am finding the transition problematic to say the least.

I am writing a class that I want to represent in XML. The XML Schema that I must conform to is fairly complicated so I have ruled out the option of using serialization. Therefore I want to use an XML stream and the XmlWriter or XmlTextWriter classes.

Fairly easy so far, however I need to be able to stream the XML via TCP/IP. Again this shouldn't be too much of a problem, but during testing I just want to display the XML in the console or in a TextBox on a form, or save the XML to a file.

My idea has been to have a function in my class called ToXML which returns a System.IO.Stream object and then I can do what I like with it the other end. But I do not know how to do this. If I create the XML using an instance of the System.Xml.XmlTextWriter then how do I just return the stream, then in the calling program, how do I display the stream, save the stream to a file, print it out to the console window or send it via TCP/IP?

Regards
Owain Williams

mehdi62b · September 6th, 2004, 02:06 PM

Hello owain,
I cant get exactly what you mean
what do you mean from this sentence

Quote:

quote:
My idea has been to have a function in my class called ToXML which returns a System.IO.Stream object and then I can do what I like with it the other end

for working with your XML file you should make a stream for it
like

Code:

FileStream fs = new FileStream("Test.xml", FileMode.OpenOrCreate, FileAccess.ReadWrite);

then you should make a XmlTextWriter object

Code:

System.Xml.XmlTextWriter xtw=new XmlTextWriter(fs,null);

as you see here we should give the constructor a stream object(FileStream)
then you can access this stream through Basestream property of your XmlTextWriter

Code:

 
//xtw.BaseStream

this baseStream is the same as the stream(or derived classes like FileStream) you declared in XmlTextWriter Constructor,
HtH.

--------------------------------------------
Mehdi.:)

owain · September 7th, 2004, 05:43 AM

Thank you for your reply. What I was trying to do was return an object of type System.IO.Stream that I could then use in the calling program, I now see the error of my way. What I am now doing (in VB.NET) is:

Code:

Public Class MyClass
    Public Sub ToXML(ByRef Stream As System.IO.Stream, _
                     ByRef Encoding As System.Text.Encoding)
        Dim xmlStream As System.Xml.XmlTextWriter
        xmlStream = New System.Xml.XmlTextWriter(Stream, Nothing)
        ' Build XML here...
    End Function

    Public Sub ToXML(ByRef Stream As System.IO.TextWriter)
        Dim xmlStream As System.Xml.XmlTextWriter
        xmlStream = New System.Xml.XmlTextWriter(Stream)
        ' Build XML here...
    End Function
End Class

I have overridden the ToXML subroutine to accept either a TextWriter or a Stream object and use this to build my XML into. This works in my calling program when I want to display the XML in the Console window by using code similar to this:

Code:

Private Sub BuildXml(ByVal sender As System.Object, _
                     ByVal e As System.EventArgs) _
                     Handles btnBuildXml.Click
    Dim xmlClass As MyClass = New MyClass
    xmlClass.ToXML(Console.Out)
End Sub

My next question is how can I change this to display the generated XML in a text box on a form? I have tried declaring an object of type System.IO.TextWriter and passing this to the ToXML subroutine, but how do I use this object when the subroutine completes to display the XML on a text box?

Another way of asking the question would be how do I use the System.Xml.XmlTextWriter to display the XML in a text box on a form?

Regards
Owain Williams

mehdi62b · September 7th, 2004, 11:40 AM

as I told you
xmlStreamWriter = New System.Xml.XmlTextWriter(Stream)
it writes to your stream ...(here your stream is Console.Out so you see them in screen)
but what does it write?something you passed them through xmlStreamWriter.WriteXXXXX methods
xmlStreamReader = New System.Xml.XmlTextWriter(Stream)
it reads from your stream now your stream should be your xml file(FileStream fs)and read from it and write it to your TextBox ....
(I'm not sure your second overridden method works correctly)

Quote:

quote:
Another way of asking the question would be how do I use the System.Xml.XmlTextWriter to display the XML in a text box on a form?

work with ur XML file like a simple TXT file and write it to ur textbox
(http://www.syncfusion.com/FAQ/WinForms/FAQ_c94c.asp)

--------------------------------------------
Mehdi.:)

owain · September 8th, 2004, 04:53 AM

Thank you for your time. The problem I have had with understanding this concept is that I know I want to use an object of type System.IO.Stream, however this class is declared as MustInherit so I have found it difficult to find the class I need to use. I am now using the System.IO.StringWriter class.

The class I am writing that generates the XML has not changed, however my calling program now does the following to display the XML in a text box on a form:

Code:

Dim xmlClass As MyClass = New MyClass
Dim myStream As System.IO.StringWriter

myStream = New System.IO.StringWriter
xmlClass.ToXML(myStream)
txtXML.Text = myStream.ToString()

Thanks again for your help.

Regards
Owain Williams