I need help with XmlReader

[ucchris77]

I am trying to create a function that uses XmlReader to get a single value from an xml file. This function is passed two parameters:

chartName: which is the name of the ChartName attribute for the <Chart> node that you are looking for.

elementName: which is the name of the element you are looking for.

For example if I wanted to get the value of goal from the Astenteeism chart I would do
Dim myString As String = getStuff("Goal","Absenteeism")
This should return 0.5 (see xml below)

But the problem is that it will return 0.8 For some reason it is grabbing the goal tag value from whatever goal tag is first. I'm not sure why?

I tried to give as much info as I could let me know if any details are confusing. Thanks for your help.

here's my code.

Private Function getStuff(ByVal chartName As String, ByVal elementName As String) As String

        Dim settings As New XmlReaderSettings
        settings.IgnoreComments = True
        settings.IgnoreWhitespace = True

        Dim myXMLFile As XmlReader = XmlReader.Create("C:\Documents and Settings\honeymoon\My Documents\2010_Config.xml", settings)

        Dim locationNameString As String
        locationNameString = Nothing

        myXMLFile.MoveToAttribute(chartName)
        myXMLFile.MoveToElement()
        myXMLFile.ReadToFollowing(elementName)
        locationNameString = myXMLFile.ReadElementContentAsString

        Return locationNameString

    End Function

Here's the xml file.

<?xml version="1.0"?> 
	<Excel>
		<Foo>
			<Chart ChartName = "Operational Availability">
				<Location>2010_OperationalAvailability.xlsm</Location>
				<Goal>0.8</Goal>
			</Chart>
			<Chart ChartName = "Absenteeism">
				<Location>2010_OperationalAvailability.xlsm</Location>
				<Goal>0.5</Goal>
			</Chart>
		</Foo>
	</Excel>

 

[JohnH]

I never get used to all those move operations either, I find XPath expressions much easier to work with, example:

Dim reader As New Xml.XPath.XPathDocument("2010_Config.xml")
Dim nav As Xml.XPath.XPathNavigator = reader.CreateNavigator
Dim xpath As String = String.Format("//Chart[@ChartName='{0}']/{1}", chartName, elementName)
Return nav.SelectSingleNode(xpath).Value

 

[MattP]

I found XPath expressions easier to work with as well.

Here's an alternate example using LINQ which I find easier to work with than XPath.

        Dim elementName As String = "Chart"
        Dim attributeName As String = "ChartName"
        Dim searchTerm As String = "Absenteeism"

        Dim xDoc = XDocument.Load("C:\Temp\chart.xml")
        Dim theChartNode = (From node In xDoc.Descendants(elementName)
                   Where node.Attribute(attributeName).Value = searchTerm).FirstOrDefault

        If theChartNode IsNot Nothing Then
            MessageBox.Show(theChartNode.<Goal>.Value)
        Else
            MessageBox.Show(searchTerm & " not found in file")
        End If

 

[ucchris77]

John I tried your suggestion and it worked perfectly. Thank you. Matt I will have to try LINQ and see if I like that too. Thanks for your help guys.

 

[MattP]

There's absolutely nothing wrong with using XPath. I still have a lot of .NET 2.0 programs running that are littered with XPath expressions and they work fantastically.

The difference for me is that I don't use XML every day while I do use SQL all day every day. Since the LINQ statement syntax is similar it takes me less time to wrap my head around the next time I have to come back to it.

The point is that there are multiple ways to skin a cat; pick one that works for you, the more alternatives you have available the better the chance you're going to find one that makes sense.