Updating an XML File in the 14 Hive Using a Custom Timer Job

Applies To: SharePoint 2010, .NET Framework (C#, VB.NET)

As mentioned in a previous post, I’ve recently put together a solution for automatically configuring your SharePoint servers to use the Adobe PDF icon for PDF files. You can download the solution as well as the source for free from CodePlex here: WireBear PDFdocIcon. I’m going to show some of the code as it currently exists below, but be sure to check out the CodePlex site to ensure you have the latest version.

I’ve also provided the bulk of the code and some explanation for installing/uninstalling a custom job from a SharePoint solution in my last post: Implementing a Custom SharePoint Timer Job. In this post we’ll explore what’s actually happening in the execution of the timer job.

The goal is to update the DOCICON.xml file in the 14\TEMPLATE\XML folder within the SharePoint 2010 Hive to include or remove a mapping entry for a specific file extension. Here is the entire DocIconJob class:

The Code:

Imports Microsoft.SharePoint.Administration
Imports System.IO
Imports Microsoft.SharePoint.Utilities
Imports System.Xml

Public Class DocIconJob
    Inherits SPServiceJobDefinition

#Region "Properties"

    Private _dociconPath As String
    Public ReadOnly Property DocIconPath() As String
        Get
            If String.IsNullOrEmpty(_dociconPath) Then _dociconPath = SPUtility.GetGenericSetupPath("TEMPLATE\XML\DOCICON.XML")
            Return _dociconPath
        End Get
    End Property

    Private Const InstallingKey As String = "DocIconJob_InstallingKey"
    Private Property _installing() As Boolean
        Get
            If Properties.ContainsKey(InstallingKey) Then
                Return Convert.ToBoolean(Properties(InstallingKey))
            Else
                Return True
            End If
        End Get
        Set(ByVal value As Boolean)
            If Properties.ContainsKey(InstallingKey) Then
                Properties(InstallingKey) = value.ToString
            Else
                Properties.Add(InstallingKey, value.ToString)
            End If
        End Set
    End Property

    Private Const FileExtensionKey As String = "DocIconJob_FileExtensionKey"
    Private Property _fileExtension() As String
        Get
            If Properties.ContainsKey(FileExtensionKey) Then
                Return Convert.ToString(Properties(FileExtensionKey))
            Else
                Return String.Empty
            End If
        End Get
        Set(ByVal value As String)
            If Properties.ContainsKey(FileExtensionKey) Then
                Properties(FileExtensionKey) = value
            Else
                Properties.Add(FileExtensionKey, value)
            End If
        End Set
    End Property

    Private Const ImageFilenameKey As String = "DocIconJob_ImageFilenameKey"
    Private Property _imageFilename() As String
        Get
            If Properties.ContainsKey(ImageFilenameKey) Then
                Return Convert.ToString(Properties(ImageFilenameKey))
            Else
                Return String.Empty
            End If
        End Get
        Set(ByVal value As String)
            If Properties.ContainsKey(ImageFilenameKey) Then
                Properties(ImageFilenameKey) = value
            Else
                Properties.Add(ImageFilenameKey, value)
            End If
        End Set
    End Property

#End Region

    Public Sub New()
        MyBase.New()
    End Sub

    Public Sub New(JobName As String, service As SPService, Installing As Boolean, FileExtension As String, ImageFilename As String)
        MyBase.New(JobName, service)
        _installing = Installing
        _fileExtension = FileExtension
        _imageFilename = ImageFilename
    End Sub

    Public Overrides Sub Execute(jobState As Microsoft.SharePoint.Administration.SPJobState)
        UpdateDocIcon()
    End Sub

    Private Sub UpdateDocIcon()
        Dim x As New XmlDocument
        x.Load(DocIconPath)

        Dim mapNode As XmlNode = x.SelectSingleNode(String.Format("DocIcons/ByExtension/Mapping[@Key='{0}']", _fileExtension))

        If _installing Then
            'Create DocIcon entry
            If mapNode Is Nothing Then
                'Create Attributes
                Dim keyAttribute As XmlAttribute = x.CreateAttribute("Key")
                keyAttribute.Value = _fileExtension
                Dim valueAttribute As XmlAttribute = x.CreateAttribute("Value")
                valueAttribute.Value = _imageFilename

                'Create Node
                mapNode = x.CreateElement("Mapping")
                mapNode.Attributes.Append(keyAttribute)
                mapNode.Attributes.Append(valueAttribute)

                Dim byExtensionNode = x.SelectSingleNode("DocIcons/ByExtension")
                Dim NodeAdded As Boolean = False
                If byExtensionNode IsNot Nothing Then
                    'Add in alphabetic order
                    For Each mapping As XmlNode In byExtensionNode.ChildNodes
                        If mapping.Attributes("Key").Value.CompareTo(_fileExtension) > 0 Then
                            byExtensionNode.InsertBefore(mapNode, mapping)
                            NodeAdded = True
                            Exit For
                        End If
                    Next

                    If Not NodeAdded Then byExtensionNode.AppendChild(mapNode)
                    x.Save(DocIconPath)
                End If
            End If
        Else
            'Remove DocIcon entry
            If mapNode IsNot Nothing Then
                Dim byExtensionNode = x.SelectSingleNode("DocIcons/ByExtension")
                If byExtensionNode IsNot Nothing Then
                    byExtensionNode.RemoveChild(mapNode)
                    x.Save(DocIconPath)
                End If
            End If
        End If
    End Sub

End Class

What’s Going On:

Lines 9-73 are just the declaration of and logic needed to persist some properties. Again more information can be found in my last post, but basically I am using the SPJobDefinition’s Properties HashTable to store my own properties as specified in the constructor. Except for in the case of the DocIconPath property which is really just wrapping up some logic to get a reference to the 14 Hive’s TEMPLATE\XML directory using the SPUtility class.

The Execute method beginning in line 86 is what is called when the Timer Job actually runs. I override this method to ensure my custom code gets called instead. My custom code really begins in the UpdateDocIcon method starting at line 90.

In lines 91-94, I load the DOCICON.xml file into and XmlDocument object and attempt to find the mapping node that applies to the appropriate file extension (In this case it’s going to be pdf).

If this job is installing (Running on Solution Activation), then I just check to see if the node was found. If so, all done! If not, then it’s time to add it. I create the node and setup it’s attributes in lines 100-108 using standard objects from the System.Xml namespace.

In order to work, the mapping node needs to be added as a child of the ByExtension element, so we find that in line 110. By default the mapping nodes are listed in alphabetical order by their extension. Since I’m anal, I use a method in lines 114-120 presented by Steve Goodyear to ensure I insert the mapping node in it’s proper position. Failing that, I add it to the end in Line 122 and save the file in line 123.

If this job is uninstalling (Running on Solution Deactivation) and the mapping exists, we delete it and save the file in lines 128-134.

Isn’t that Super Exciting?!?! Hopefully this example will help make the concepts I was talking about in my previous post make some sense. If not, then sadness will fill my soul and flowers will no longer bloom or something.

3 thoughts on “Updating an XML File in the 14 Hive Using a Custom Timer Job

    • @Michael I investigated several ways of doing this and found that only a timer job would allow my changes to be propagated to all my web servers. Just doing this on either the activation/deactivation or install/uninstall events only affected a single server. A good example of the solution you propose can be found here. If you read through the comments or run the code you’ll see the problem I am referring to.

      The good news is that the simple timer job shown above takes care of this issue by running on each server and since it is only run on feature activation/deactivation, it’s really not much different than just running this code in those events. The main difference is that it works, which is always a good thing! Thanks for your comments!

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