Programmatically create a SharePoint XsltListViewWebPart, with Cross-Site support

Since I've found a few very helpful pieces of code this week, including the SharePoint 2010 Batch Property Edit control, that my friends of Tam Tam generously uploaded to CodePlex, I though that I'll share the XsltListViewWebPart that I've recently built for a client of ours.

 

After Googling for days it seemed, I couldn't find a good example of a programmatically created XsltListViewWebPart.  Below I'll share a few thoughts on what I did to get the control up and running.  I've also added the functionality to display a "Add new item" link, the same way the OOTB SharePoint List WebPart does.

 

Although by no means perfect, I hope this does help someone in desperate need of answers.  Remember, this is not a copy-paste exercise, but a gentle nudge in the right direction!

 

Public and Private properties
Nothing too special here.  Give the user the ability to select a Web, List and View combination, plus the option to show or hide the "Add new item" link.  

 

 

// User can set the WebId
public string WebId { get; set; }

// User can set the ListId
public string ListId { get; set; }

// User can set the ViewId
public string ViewId { get; set; }

// User can set a custom XslFile path
public string XslLink { get; set; }

// User can choose to display the "Add item" link
public bool HideAddLink { get; set; }

// Check if all requirements are met to display the "Add item" link
private bool HasValidButtonProperties
{
 get
 {
  return base.HasWebIdAndListIdAndViewId && !this.HideAddLink;
 }
}

// Unique key generation
private string OpenScriptedDialog
{
 get
 {
  return string.Format("OpenXsltListViewerControl{0}", this.ClientID);
 }
}

// Use panel/updatepanel to add the XsltListViewWebPart
protected UpdatePanel updatePanel;
protected Panel panel;

 

OOTB not working?  Aaaaaaargh!

TIP:  I've tried setting the XSL Link on a OOTB SharePoint list web part, but it doesn't seem to work!?  Is it just me or does anyone else have issues with this?  By rendering this custom XsltListViewWebPart and setting its XslLink property I could get the XslLink rendering working.  But not the OOTB list web part?

 

UPDATE (01/10/2012) : The problem (bug if you will) with using the XSL Link on a List Part, is better explained over at Glyn Clough's blog.  Just follow the these two links.

• Overriding the presentation of an XSLT List View Web Part
• XLV Bug: XSL Link Property and the ECB Menu

 

Overrides
The only real override to take note of, the the CreateChildControls method.  Here I use a few helper functions to render all the plumbing necessary for the SP.UI.ModelDialog.  This is needed to display the "Add new item" dialog.  I've used a series of fixed values, but obviously you can make them all dynamic and have the user set them in your EditorPart.

 

protected override void OnInit(EventArgs e)
{
 // Init update panel
 updatePanel = new UpdatePanel();
 updatePanel.ChildrenAsTriggers = true;
 updatePanel.UpdateMode = UpdatePanelUpdateMode.Conditional;
 updatePanel.ID = string.Format("updatePanel_{0}", this.ClientID);

 // Init panel
 panel = new Panel();

 base.OnInit(e);
}

protected override void CreateChildControls()
{
 // WebPart base ensures selected variables 
 base.CreateChildControls();

 // Register Scripts
 StringBuilder sb = new StringBuilder();

 if (HasValidButtonProperties)
 {
  // Use helper function to inject javascript for the SP.UI.ModalDialog add functionality 
  sb.Append(SPUtilities.GetModalDialogScript(this.ListId + "/NewForm.aspx",
              "New Item",
              625,
              525,
              this.OpenScriptedDialog));
 }
 // Helper function to register script
 base.RegisterScript(base.UniqueScriptsKey, sb.ToString());

 // Add the control to the controls collection, not the panel, 
 // this will ensure that the "Add link" is shown at the bottom of the control.
 if (HasValidButtonProperties)
 {
  Use a helper function to render the "Add link"
  this.Controls.Add(new LiteralControl(SPUtilities.GetModalDialogAddButton(this.OpenScriptedDialog)));
 }
}

protected override void OnLoad(EventArgs e)
{
 RefreshXsltListViewer();
 base.OnLoad(e);
}

 

Helper functions
I've included the SP.UI.ModelDialog helper functions.  They're all but perfect (but works!), so feel free to dice and slice them according to your own needs. Again I've included them just to give you an idea of what I've done.

 

// Method injects javascript to handle the SP.UI.ModalDialog functions 
public static string GetModalDialogScript(string url, string title, int width, int height, string functionName)
{
 var sb = new StringBuilder();
 var _width = width > 0 ? width : 625;
 var _height = height > 0 ? height : 325;

 sb.Append(" ");

 return sb.ToString();
}

// Method renders the 'Add new item link'
public static string GetModalDialogAddButton(string addLinkKey)
{
 return GetModalDialogAddButton(addLinkKey, string.Empty);
}

// Method renders the 'Add new item link'
public static string GetModalDialogAddButton(string addLinkKey, string addLinkText)
{
 if (string.IsNullOrEmpty(addLinkKey))
  return string.Empty;

 if (string.IsNullOrEmpty(addLinkText))
  addLinkText = "Add new item";
 
 StringBuilder sb = new StringBuilder();
 sb.Append("<table width='100%'>");
 sb.Append("  <tr>");
 sb.Append("    <td class='ms-partline'>");
 sb.Append("      <img height='1' width='1' alt='' src='/_layouts/images/blank.gif'>");
 sb.Append("    </td>");
 sb.Append("  </tr>");
 sb.Append("  <tr>");
 sb.Append("     <td style='padding-bottom: 3px' class='ms-addnew'>");
 sb.Append("       <span class='s4-clust' style='height:10px;width:10px;position:relative;display:inline-block;overflow:hidden;'>");
 sb.Append("           <img style='left:-0px !important;top:-128px !important;position:absolute;' alt='' src='/_layouts/images/fgimg.png'>");
 sb.AppendFormat(" </span>&nbsp;<a href='javascript:{0}()'>{1}</a>", addLinkKey, addLinkText);
 sb.Append("     </td>");
 sb.Append("  </tr>");
 sb.Append("</table>");

 return sb.ToString();
}

 

Private methods
So here comes the juicy bits.  First its important to notice that the CreateXsltListViewer method runs with an elevated privilaged SPWeb and UnsafeUpdates set to true.  I've created a series of extension methods to handle this for me. (If your'e a bit confused about this, see the helpful links section at the bottom of this page for more information.)

 

In order to create and render a cross-site list, you'll simply need to include the WebId, ListName, ListId and ViewGuid properties.  Personally thought it might be a bit more complex, but that was it...

 

Since the toolbar itself becomes way too much of a problem in its complexity, I've decided not to display it.  All the elements inside the list can still be served by its dropdown menu, but unfortunately not the Ribbon.  If you're in dire need of this functionality, happy hunting, and do drop me a line if you've figured it out! ;-)

 

private void RefreshXsltListViewer()
{
  // Run the CreateXsltListViewer method with an 
  // elveated privilaged web, that also caters for
  // unsafe-updates.
  SPWeb web = SPContext.Current.Site.OpenWeb(WebId);
  web.UnsafeUpdate(CreateXsltListViewer);
}

private void CreateXsltListViewer(SPWeb web)
{
 // Use helper function to get the SPList
 SPList list = SPUtilities.GetSPList(ListId);

 // Use list acquired from AllowUnsafeUpdates web
 SPList viewList = web.Lists[list.ID];
 
 // Create the control
 XsltListViewWebPart xsltControl = CreateXsltListViewerInstance(viewList, ViewId);

 // Add control to the update panel
 if (xsltControl != null)
 {
  panel.Controls.Add(xsltControl);
 }
 else
 {
  panel.Controls.Add(new LiteralControl("There was an error creating the XsltListViewer."));
 }
}

private XsltListViewWebPart CreateXsltListViewerInstance(SPList list, string viewName)
{
 XsltListViewWebPart xsltListViewWebPart = new XsltListViewWebPart();

 // First check if view acutally exists
 if (list.Views.Exists(viewName))
 {
  SPView defaultView = list.Views[viewName];

  xsltListViewWebPart.ID = "wpListView";
  // We're displaying this WebPart inside a WebPart. Disable the 
  // XsltListViewWebPart's own Title and ChromeType.
  xsltListViewWebPart.Title = string.Empty; 
  xsltListViewWebPart.ChromeType = System.Web.UI.WebControls.WebParts.PartChromeType.None;
  
  // Set all these properties to allow for Cross-Site lookups
  xsltListViewWebPart.WebId = list.ParentWeb.ID;
  xsltListViewWebPart.ListName = list.ID.ToString("B").ToUpper();
  xsltListViewWebPart.ListId = list.ID;
  xsltListViewWebPart.ViewGuid = defaultView.ID.ToString("B").ToUpper();

  // If required, set the XSL file link
  if (!string.IsNullOrEmpty(XslLink))
  {
   xsltListViewWebPart.XslLink = this.XslLink;
  }

  defaultView.Update();
  
  // I never show the toolbar
  SetToolbarType(xsltListViewWebPart, "None");
 }

 return xsltListViewWebPart;
}

public void SetToolbarType(XsltListViewWebPart lvwp, string viewType)
{
 try
 {
  MethodInfo ensureViewMethod = lvwp.GetType().GetMethod("EnsureView", BindingFlags.Instance | BindingFlags.NonPublic);
  object[] ensureViewParams = { };
  ensureViewMethod.Invoke(lvwp, ensureViewParams);
  FieldInfo viewFieldInfo = lvwp.GetType().GetField("view", BindingFlags.NonPublic | BindingFlags.Instance);
  SPView view = viewFieldInfo.GetValue(lvwp) as SPView;
  Type[] toolbarMethodParamTypes = { Type.GetType("System.String") };
  MethodInfo setToolbarTypeMethod = view.GetType().GetMethod("SetToolbarType", BindingFlags.Instance | BindingFlags.NonPublic, null, toolbarMethodParamTypes, null);
  object[] setToolbarParam = { viewType }; //set the type here
  setToolbarTypeMethod.Invoke(view, setToolbarParam);
  view.Update();
 }
 catch { }
}

 

Conclusion
So there it is.  Hope this will give you some ideas on your own version of a custom XsltListViewWebPart, that supports cross-site lookups, and have the ability to have custom XSL applied to it (see below).

 

 
Important and Useful Links:

• Elegant SPSite Elevation by Keith Dahlby
• Best practices for RunWithElevatedPrivileges on StackOverflow
• XSLTListViewWebpart in Sharepoint 2010 Uncovered by Sunil Singhal
• Cross-Site (Web) XsltListViewWebPart by Thomas Zepeda McMillan
• Programmatically enable Ajax Auto Refresh on a SharePoint XsltListViewWebPart by Brian Cartmel