How to update a global variable XmlTextWriter, from a local process in VB.NET?

Question

How to update a global variable XmlTextWriter, from a local process in VB.NET?

LA RC 41

I am trying to build an XML file, where I generate a variable type XmlTextWriter in the main class, to be able to read it globally. Then, inside a NavButton, I create a new variable with the same name and send it the path attribute so that it generates the file within a specific path.

When I get to the conditional if it is TRUE, it enters the function and sends 4 parameters, which the function receives correctly, but when it starts to write inside the XML, it does not send an error and continues fine, but when opening the XML already when finished, is empty and only with two lines.

I understand that you would be talking about two variables with the same name, but one global and one local and both have different paths.

My question is, how can I update the attribute or path of the global variable, from the local one and pass it the correct path so that the function writes in the XML that it should be?

This is my code:

Public Class Form1
    Dim path As String = "0"
    Dim writerC As New XmlTextWriter(path, System.Text.Encoding.UTF8)
End Class


Private Sub NavButton1_ElementClick(sender As Object, e As NavElementEventArgs) Handles NavButton1.ElementClick

    Dim pathRoot as String = "C:\Temp"        

    Dim strPathC As String = pathRoot & "\" & "e" & TextBox1.Text & ".XML"

        Dim writerC As New XmlTextWriter(strPathC, System.Text.Encoding.UTF8)

        writerC.WriteStartDocument(True)

        writerC.Formatting = Formatting.Indented
        writerC.Indentation = 2

        writerC.WriteStartElement("PageCollection") '---PageCollection---

        if i = 0 then

            sheetTest("A", "B", "C", "D")

        end if

        writerC.WriteEndElement() '---PageCollection/---
        writerC.Close() '---CLOSING XML FILE/---

        pathRoot = pathRoot & "\" & "SentFiles"
        Directory.CreateDirectory(pathRoot)


        MsgBox("Successfully generated files.", MsgBoxStyle.Information + MessageBoxButtons.OK, "TEST")
End Sub


Public Function sheetTest(firstParameter as string, secondParameter as string, thirdParameter as string, fourthParameter as string)

        writerC.WriteStartElement("Page") '---Page---

        writerC.WriteStartElement("Collection") '---Collection---

        writerC.WriteEndElement() '---Collection/---

        writerC.WriteEndElement() '---Page/---

End Function

Thank you for your time and attention.

Regards.

Accepted answer

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Your answer

Answer 1

Hi @LA RC ,
In your code , sheetTest accesses global variables, while NavButton1 accesses local variables.
You can make global variables public, and then initialize and assign values to them when you use them.
Here are my test result and test code which you can refer to.

    Public writerC As XmlTextWriter  
    Private Sub NavButton1_Click(sender As Object, e As EventArgs) Handles NavButton1.Click  
        Dim pathRoot As String = "C:\Users\lijiachenl\source\repos\Case22.4.1\WindowsApp2\"  
        Dim strPathC As String = pathRoot & "\" & "e" & TextBox1.Text & ".XML"  
        writerC = New XmlTextWriter(strPathC, System.Text.Encoding.UTF8)  
        writerC.WriteStartDocument(True)  
  
        writerC.Formatting = Formatting.Indented  
        writerC.Indentation = 2  
  
        writerC.WriteStartElement("PageCollection") '---PageCollection---  
  
        'If i = 0 Then  
  
        sheetTest("A", "B", "C", "D")  
  
        'End If  
  
        writerC.WriteEndElement() '---PageCollection/---  
        writerC.Close() '---CLOSING XML FILE/---  
  
        pathRoot = pathRoot & "\" & "SentFiles"  
        Directory.CreateDirectory(pathRoot)  
  
  
        MsgBox("Successfully generated files.", MsgBoxStyle.Information + MessageBoxButtons.OK, "TEST")  
        Dim fs As New FileStream(strPathC, FileMode.Open, FileAccess.Read)  
        Dim data(fs.Length) As Byte  
        fs.Read(data, 0, fs.Length)  
        Console.WriteLine(Encoding.UTF8.GetChars(data))  
    End Sub  
    Public Function sheetTest(firstParameter As String, secondParameter As String, thirdParameter As String, fourthParameter As String)  
  
        writerC.WriteStartElement("Page") '---Page---  
  
        writerC.WriteStartElement("Collection") '---Collection---  
  
        writerC.WriteEndElement() '---Collection/---  
  
        writerC.WriteEndElement() '---Page/---  
  
    End Function

Hope these could be helpful.
Best Regards.
Jiachen Li

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Answer 2

A couple of things.

When working with paths use IO.Path.

When working with XML you might find XElement easier to use.

        Dim pathRoot As String = "C:\Temp"  
        Dim strPathC As String  
        strPathC = IO.Path.Combine(pathRoot, "e", TextBox1.Text)  
        strPathC = IO.Path.ChangeExtension(strPathC, "xml")  
  
        Dim myXML As XElement  
        'using XML Literal  
        myXML = <PageCollection>  
                    <Page></Page>  
                    <Collection></Collection>  
                </PageCollection>  
  
        myXML.Save(strPathC)  
        Stop 'look at myXML

You can even use literals with LINQ queries in embedded expressions,

        Dim pathRoot As String = "C:\Temp"  
        Dim strPathC As String  
        strPathC = IO.Path.Combine(pathRoot, "e", TextBox1.Text)  
        strPathC = IO.Path.ChangeExtension(strPathC, "xml")  
  
        Dim someVal() As String = {"A", "B", "C", "Z"}  
        Dim myXML As XElement  
        'using XML Literal  
        myXML = <PageCollection>  
                    <Page></Page>  
                    <Collection>  
                        <%= From v In someVal  
                            Where v <> "B"  
                            Select <Col><%= v %></Col>  
                        %>  
                    </Collection>  
                </PageCollection>  
  
        myXML.Save(strPathC)  
        Stop 'look at myXML

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How to update a global variable XmlTextWriter, from a local process in VB.NET?

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