Reading from an XML document

[ericstein81]

Hey all,

I have a program that is saving information into and XML file that is later read from to continue the users progress. I am having trouble getting the reader to work without an error

This is the code that I am having trouble with and below is the error. Thanks for the help!

Dim xmldoc As XmlDataDocument = New XmlDataDocument
 
xmldoc.Load("please.xml")
 
 TextBox1.Text = xmldoc.SelectSingleNode("form1/text").InnerText
TextBox1.BackColor = System.Drawing.ColorTranslator.FromHtml(xmldoc.SelectSingleNode("form1/color").InnerText)
TextBox2.Text = xmldoc.SelectSingleNode("form1/text").InnerText
TextBox2.BackColor = System.Drawing.ColorTranslator.FromHtml(xmldoc.SelectSingleNode("form1/color").InnerText)

System.NullReferenceException was unhandled
Message="Object reference not set to an instance of an object."
Source="WindowsApplication2"
StackTrace:
at WindowsApplication2.Form1.Button2_Click(Object sender, EventArgs e) in d:\Users\steinmetze\Documents\Visual Studio 2008\Projects\WindowsApplication2\WindowsApplicati on2\Form1.vb:line 100
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventAr gs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.O nMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.W ndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallba ck(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchM essageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager. System.Windows.Forms.UnsafeNativeMethods.IMsoCompo nentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.Run MessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.Run MessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(ApplicationCo ntext context)
at Microsoft.VisualBasic.ApplicationServices.WindowsF ormsApplicationBase.OnRun()
at Microsoft.VisualBasic.ApplicationServices.WindowsF ormsApplicationBase.DoApplicationModel()
at Microsoft.VisualBasic.ApplicationServices.WindowsF ormsApplicationBase.Run(String[] commandLine)
at WindowsApplication2.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.Run UsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context( Object state)
at System.Threading.ExecutionContext.Run(ExecutionCon text executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException:

[vekipeki]

SelectSingleNode(xpath) returns null if xpath expression is not found. Are you sure that "form1/text" is a valid xpath expression for your schema?

Check this link for some clues: Select Nodes Using XPath Navigation

[jkmyoung]

I would also advise having a try-catch around your code if you are going to be calling functions on nodes before checking that they are null.
If you post part of your xml, we might also be able to help.