Category Archives: C#

Get a Distinct List from ADO.Net DataSet Using Linq

There are some sample .Net functions out there to pull a list of distinct items from an ADO.Net DataTable, but none of them I found take advantage of LINQ.  So I thought I would post something I came up with to fill the gap.

In the code sample below, the goal is to pull a list of distinct values from a single column in a DataTable.  There are a few ways to approach this, depending on the end-game.  I listed 4 options, 2 with LINQ syntax and their Lambda expression twins.

// —————————————————————–
// Build a list DataTable to test
// —————————————————————–
DataTable tbl = new DataTable();
tbl.Columns.Add(“Title”, typeof(string));
for (int i = 1; i <= 100; i++)
    // Add 1 row
    DataRow row1 = tbl.NewRow();
    row1["Title"] = string.Format(“Title {0}”, i);

    // Add duplicate row
    DataRow row2 = tbl.NewRow();
    row2["Title"] = string.Format(“Title {0}”, i);

    // Add null row for testing
    DataRow row3 = tbl.NewRow();
    row3["Title"] = DBNull.Value;

// —————————————————————–
// All four of these examples yield the same results
// Each returns a list of 100 distinct rows
// Pick your poison!
// —————————————————————–

// Sample 1
// —————————————————————–
// Get a distinct list of titles
// Linq syntax against the DataTable using
// This is functionally the same as the 2nd example
List<string> distinctTitles2 =
        (from r in
            where !string.IsNullOrEmpty(r.Field<string>(“Title”))
            select r.Field<string>(“Title”)).Distinct().ToList();

// Sample 2
// —————————————————————–
// Get a distinct list of titles
// Lambda expression against the DataTable 
// This is functionally the same as the 1st example
List<string> distinctTitles1 = ((IEnumerable<DataRow>)tbl.AsEnumerable())
            .Select<DataRow, string>(r => r.Field<string>(“Title”))
            .Where(title => !string.IsNullOrEmpty(title))

// Sample 3
// —————————————————————–
// Get a distinct list of titles
// On this one, I’m using the tbl.Select() method to get an array of DataRows matching filter criteria
// Linq expression is then used against the DataRow array to get distinct titles
// This is functionally the same as the 4th example
List<string> distinctTitles4 =
        (from r in
        tbl.Select(“Title IS NOT NULL And TRIM(Title) <> ””)
        select r.Field<string>(“Title”))

// Sample 4
// —————————————————————–
// Get a distinct list of title
// On this one, I’m using the tbl.Select() method to get an array of DataRows matching filter criteria
// Lambda expression against the DataRow array to get distinct titles
// This is functionally the same as the 3rd example
List<string> distinctTitles3 = tbl.Select(“Title IS NOT NULL And TRIM(Title) <> ””)
        .Select(r => r.Field<string>(“Title”))

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COM Interop – QueryInterface not supported (E-NOINTERFACE)


Encountering an error when trying to instantiate COM objects through Primarary Interop Assemblies (PIA’s) or Runtime Callable Wrappers (RCW’s) created using the TLBIMP.exe tool. 

When calling the object for the first time, you encounter the following COM exception:

Unable to cast COM object of type ‘xxx to interface type ‘xxx’. This operation failed because the QueryInterface call on the COM component for the interface with IID ‘{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}’ failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

You are likely to encounter this problem when developing ASP.Net applications, Windows Console applications, or Windows Services.  You are unlikely to experience this issue when developing Windows Forms applications.


The problem is that you are attempting to call Single-Threaded Apartment (STA) model COM components from an Multi-Threaded Apartment (MTA) thread.  The primary thread of Windows Forms applications are STA threads, so the components work fine there.  Most other project types, including Console applications and Windows Service applications are run on an MTA thread by default.  When you attempt to instantiate the an STA component, you will get the ubiquitous error described above.

You might try calling System.Threading.Thread.CurrentThread.SetApartmentState(ApartmentState.STA), but this won’t work.  You cannot change the thread execution model on a running thread. 

To fix the problem, you can set the thread execution type on the main application thread before it is started, but this is not optimal.  It is better to set the threading model specifically for the portion of code that needs it.

A better solution is to spin up a new thread for the job at hand, and set the thread execution state on the new thread before executing it.  There are a few different methods to accomplish this depending on what you’re trying to accomplish.  Here’s one to get you started:

using System.Threading;

// Setup an object to host the thread entry point
// Start a process on an MTA thread 
MyThreadedJob jobHost = new MyThreadedJob(jobId);
Thread t = new Thread(new ThreadStart(MyThreadedJob.Execute));

// Start the thread

// Wait for thread to complete (optional)


More Gory Details

For more of the gory details and differences between threading models in Windows and COM, you can start here. it! digg it! reddit! technorati! yahoo!

SharePoint 2007 – Get SPList Object by Url

I want to get a reference to a SPList object associated with a given list url.  This method works with any of the url’s associated with the list, including view page url’s, or list form url’s. 

This should be much easier to achieve by using the object model, in my opinion.  String parsing of the url is not my favorite, but I couldn’t find a better way to accomplish it. 

If you know of an easier way to accomplish this, please leave me a comment.  Otherwise, you can steal this from me, if you want it!

/// <summary>
/// Gets an SPList based on the url to the list
/// </summary>
/// <param name="listUrl">Full url to the list</param>
/// <returns>SPList object, null if list is not found</returns>
public SPList GetListByUrl(string listUrl)
    SPList list = null;

        using (SPSite site = new SPSite(listUrl))
            if (site != null)
                // Strip off the site url, leaving the rest
                // We'll use this to open the web
                string webUrl = listUrl.Substring(site.Url.Length);

                // Strip off anything after /forms/
                int formsPos = webUrl.IndexOf("/forms/", 0, StringComparison.InvariantCultureIgnoreCase);
                if (formsPos >= 0)
                    webUrl = webUrl.Substring(0, webUrl.LastIndexOf('/', formsPos));

                // Strip off anything after /lists/
                int listPos = webUrl.IndexOf("/lists/", 0, StringComparison.InvariantCultureIgnoreCase);
                if (listPos >= 0)
                    // Must be a custom list
                    // Strip off anything after /lists/
                    webUrl = webUrl.Substring(0, webUrl.LastIndexOf('/', listPos));
                    // No lists, must be a document library.
                    // Strip off the document library name
                    webUrl = webUrl.Substring(0, webUrl.LastIndexOf('/'));

                // Get the web site
                using (SPWeb web = site.OpenWeb(webUrl))
                    if (web != null)
                        // Initialize the web (avoids COM exceptions)
                        string title = web.Title;

                        // Strip off the relative list Url
                        // Form the full path to the list
                        //string relativeListUrl = listUrl.Substring(web.Url.Length);
                        //string url = SPUrlUtility.CombineUrl(web.Url, relativeListUrl);

                        // Get the list
                        list = web.GetList(listUrl);
    catch { }

    return list;

Enjoy! it!

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SharePoint TechFest 2009 – Dallas, TX

I want to thank everyone who attended my session on SharePoint Workflow with Visual Studio at our TechFest event yesterday.  Please feel free to post any comments (good or bad) about my presentation or the event. 

Demo source code is posted on Nakido until the Techfest site is updated with session content.

SharePoint WorkFlow with Visual Studio – Downloads

SharePoint WorkFlow with Visual Studio – References it! digg it! reddit! technorati! yahoo!

Visual Studio 2008 Workflow Project Wizard – SharePoint Not Installed


I’m creating a SharePoint Sequential Workflow using Visual Studio 2008 (SP1) with .Net 3.5 SP1 installed.  This is on a Windows 2003 R2 VPC with SharePoint 2007 (MOSS Enterprise) installed on the local machine for development.  A Collaboration Portal is installed on a web site with host headers (portal) assigned to port 80.

When I create a new workflow project, the wizard asks for a path to the SharePoint site.  I type in my url (http://portal in my case), and the project wizard fails, saying “SharePoint server not installed. Please run Microsoft Office SharePoint Server 2007 setup.”  


I’m logged in as the farm administrator.  I thought it might be a permissions issue (my farm admin doesn’t have full rights on the domain), so I went back and gave it full Domain Admin rights in case that was the problem.  Still failing!!

What the hell?


It turns out that the wizard does some funny business behind the scenes, calling the database directly.  When I give my development account (farm admin) account full rights (dbo) to the SharePoint content database for my portal site, bingo!  Works like a champ. 

After only an hour or two spinning my wheels.  Sigh…. it! digg it! reddit! technorati! yahoo!

SharePoint 2007 API – How To Change Layout and Publish Page

The hardest part about this (by far) is figuring out how to publish the page after you’ve made your changes.   Every time I need to do it, I have to dig up some old code.

Thought I’d blog it this time, to make it easier on myself next time around.

using Microsoft.SharePoint;
using Microsoft.SharePoint.Publishing;

using (SPSite site = new SPSite("http://portal"))
    SPWeb web = site.RootWeb;

    // Check to ensure the web has publishing turned on
    if (!PublishingWeb.IsPublishingWeb(web))
        throw new ApplicationException("Web does not have publishing enabled");

    // Get a reference to the publishing web and publishing site    
    PublishingWeb pubWeb = PublishingWeb.GetPublishingWeb(web);
    PublishingSite pubSite = new PublishingSite(web.Site);

    // Get page layout from the page layouts collection    
    PageLayoutCollection siteLayouts = pubSite.GetPageLayouts(false);
    PageLayout myLayout = siteLayouts["/_catalogs/masterpage/MyLayout.aspx"];

    // Get a reference to a publishing page
    PublishingPageCollection pages = pubWeb.GetPublishingPages();
    PublishingPage page = pages["pages/default.aspx"];
    // Check out the list item as needed
    bool forceCheckout = page.ListItem.ParentList.ForceCheckout;
    if (forceCheckout)
        // Is the page checked out?
        if (page.ListItem.File.CheckedOutBy != null)
            // Throw an exception if the page is checked out
            string pageCheckedOut = string.Format("Page {0} is checked out by {1}", page.Url, page.ListItem.File.CheckedOutBy);
            throw new SPException(pageCheckedOut);

        // Check out the page

    // Change the page layout
    page.Layout= myLayout;

    // Update the page and check in changes

    // Publish the page
    // This handles the page checkin and publishing the draft
    ApprovePublishingPage(page, "Modified page layout");


/// <summary>
/// Approves changes to a publishing page
/// </summary>
/// <param name="page">PublishingPage with changes to be published</param>
/// <param name="comment">Comment associated with the change</param>
public void ApprovePublishingPage(PublishingPage page, string comment)
    // Check in the page if required
    SPFile pageFile = page.ListItem.File;
    if (pageFile.Level == SPFileLevel.Checkout)
        pageFile.CheckIn(comment, SPCheckinType.MajorCheckIn);

    // Skip these steps if the parent list doesn't support moderation
    if (page.ListItem.ParentList.EnableModeration)
        // If page is in "pending" status, approve it
        SPModerationInformation modInfo = page.ListItem.ModerationInformation;
        if (modInfo.Status == SPModerationStatusType.Pending)

        // If page is in draft status, publish it
        if (modInfo.Status == SPModerationStatusType.Draft)

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WPF XAML Markup – How Do I Preserve Whitespace Characters?

An issue you’re likely to run into in XAML (WPF, XBAP, and SIlverlight applications) is the need to keep whitespace characters intact in your markup.  By default, XML collapses all whitespace, ignoring strings of spaces, tabs, and return characters inside an XML node, which it graciously converts to a single space.

If you want to include a series of spaces in your XML node markup, you can add a xml:space=”preserve” attrbute to your XML elements.  This attribute  is part of the XML standard.  If you turn it on, it preserves all whitespace appearing inside the XML node, including any hard return characters included inside the XML node.

<Button Name="btnSample" xml:space=preserve">Respects my      spaces
and carraige return</Button> it! digg it! reddit! technorati! yahoo!