Read & Write XML

[marcmc]

Hi, I hope to create a XML file that will hold my Connection data to a SQL Db.
I want to write an XML file from 4 Text Box named UserName, Password,
Database & Server and later read from it. My XMLSchema elements are named
dbLogin, dbPassword, dbDatabase & dbServer

I receive a 'System.NullRef erenceException Info: Object refernece not set to
an instance of an object' on the following line of code: dtSettings =
Settings.Tables ("Settings")

My Code:

Private Sub btnApply_Click( ....

Dim dsSettings As DataSet
Settings = New DataSet
Settings = dsSettings

Dim dtSettings As New DataTable
dtSettings = Settings.Tables ("Settings")

UserName.DataBi ndings.Add("Tex t", dtSettings, "dbLogin")
Password.DataBi ndings.Add("Tex t", dtSettings, "dbPassword ")
Database.DataBi ndings.Add("Tex t", dtSettings, "dbDatabase ")
Server.DataBind ings.Add("Text" , dtSettings, "dbServer")

Dim drNewRow As DataRow
drNewRow = dtSettings.NewR ow
drNewRow("dbLog in") = UserName.Text
drNewRow("dbPas sword") = Password.Text
drNewRow("dbDat abase") = Database.Text
drNewRow("dbSer ver") = Server.Text

If dtSettings.Rows .Count() > 1 Then
dtSettings.Rows .RemoveAt(0) ' Remove old row for any
previous users
End If

dtSettings.Acce ptChanges()

Dim fs As FileStream = New FileStream(Sett ingsFileName,
FileMode.Create , FileAccess.Read Write)
Dim xtw As XmlTextWriter = New XmlTextWriter(f s,
System.Text.Enc oding.Unicode)
Settings.WriteX ml(xtw, System.Data.Xml WriteMode.Write Schema)
xtw.Close()

End Sub

Am I approaching this the correct way. I have my schema set up and the

[marcmc]

My last thread may have been a bit misleading. I added a New before the
Declaration of dsSettings but then I received a 'System.Argumen tNullException
Info: Value cannot be Null' on the following line of code:
UserName.DataBi ndings.Add("Tex t", dtSettings, "dbLogin")

It seems dtSettings IsNothing. I am stumped, please help.

[Cor Ligthert [MVP]]

Marcmc,

I assume that you are not using a strongly typed dataset than

I have beneath tried to make code from what you had (in this message).
However what you do is an terrible insecure method. In my opinion should you
never should store usernames and passwords in an XML file.

\\\
Private dsSettings As New DataSet
Private form_load...... ........
Dim dtSettings As New DataTable
dsSettings.Tabl es.Add(dtSettin gs)
dtSettings.Colu mns("dbLogin",G ettype(system.S tring))
dtSettings.Colu mns("dbPassword "",Gettype(syst em.String))
dtSettings.Colu mns("dbDatabase "",Gettype(syst em.String))
dtSettings.Colu mns("dbServer"" ,Gettype(system .String))

UserName.DataBi ndings.Add("Tex t", dtSettings, "dbLogin")
Password.DataBi ndings.Add("Tex t", dtSettings, "dbPassword ")
Database.DataBi ndings.Add("Tex t", dtSettings, "dbDatabase ")
Server.DataBind ings.Add("Text" , dtSettings, "dbServer")

Dtsettings.Add( dtSettings.NewR ow)

ButtonClick event
BindingContext( dsSettings.Tabl es(0).EndCurren tEdit
dsSettings.Writ eXML
///
As your code did not, does this as well not read an XML file by the way.

I hope this helps,

Cor

[Chris Dunaway]

Your code is a little confusing:

Dim dsSettings As DataSet Here you declare dsSettings as a DataSet. It is still nothing at this
point
Settings = New DataSet Here you assign the Settings variable to a New DataSet... (You don't
need New here since you are going to reassign this variable in the next
line anyway)
Settings = dsSettings But here you discard the new DataSet you created in the previous line
and re-assign it to dsSettings, which is nothing, therefore, Settings
is now nothing.
Dim dtSettings As New DataTable Here you assign dtSettings to a New DataTable. You don't need New on
this line since you are going to assign a reference in the next line.
dtSettings = Settings.Tables ("Settings")

And finally here you try do discard the new DataTable that you created
in the previous line and set it to the "Settings" table of the dataset.
But since Settings is still nothing at this point, you get your error.

Hope this helps

[marcmc]

Thanks guys I got it with the code below

I have posted a new thread on how to use this configuration file throughout
my application. In other words I dont want to hard code into MyApp the Sql
connection data as i would like it to be as portable as possible. Don't stop
now, I'm nearly there!

Marc
Private Sub btnApply_Click( ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles btnApply.Click
If UNameMIS = "admin_mis" Then

' Load & Read the XMLSchema
Dim fileName As String = "C:\Documen ts and
Settings\marc.m cguckian\My Documents\Visua l Studio Projects\MIS RECON
Engine\MISRE_XM LSchema.xsd"

If Not File.Exists(fil eName) Then
MessageBox.Show ("Schema structure cannot be found")
Return
End If

Dim fs As FileStream = New FileStream(file Name, FileMode.Open,
FileAccess.Read )
Dim xtr As XmlTextReader = New XmlTextReader(f s)
dsSettings = New DataSet
dsSettings.Read XmlSchema(xtr)
xtr.Close()

' Write to the XMLFile
Dim dtSettings As DataTable = dsSettings.Tabl es("Settings")
Dim drSettings As DataRow

drSettings = dtSettings.NewR ow()
drSettings("dbL ogin") = UserName.Text
drSettings("dbP assword") = Password.Text
drSettings("dbD atabase") = Database.Text
drSettings("dbS erver") = Server.Text
dtSettings.Rows .Add(drSettings )

dsSettings.Acce ptChanges()

Dim SettingsFile As String = txtPollDirector y.Text + "MISRE.xml"
fs = New FileStream(Sett ingsFile, FileMode.Create ,
FileAccess.Read Write)
Dim xtw As XmlTextWriter = New XmlTextWriter(f s,
System.Text.Enc oding.Unicode)
dsSettings.Writ eXml(xtw, System.Data.Xml WriteMode.Write Schema)
xtw.Close()

sbMIS.Text = "MISRE.xml File Generated"
dbProps.MyUserN ame = Me.UserName.Tex t
dbProps.MyPassw ord = Me.Password.Tex t
dbProps.MyDatab ase = Me.Database.Tex t
dbProps.MyServe r = Me.Server.Text

Me.ClientSize = New System.Drawing. Size(584, 435)
pnlProperties.V isible = False
btnProperties.E nabled = True
btnApply.Visibl e = False
btnCancel.Visib le = False

PollDirectory = txtPollDirector y.Text

Else
sbMIS.Text = "Use buttons to navigate the application (e.g.)
[Properties sets the database and log parameters]."
End If
End Sub