The solution is offline because its associated Team Foundation Server is offline

When opening a solution in Visual Studio 2008, I kept getting the following message in the Output window:

This solution is offline.  [Team Foundation Server:
http://server:8080/]
The solution is offline because its associated
Team Foundation Server is offline.

I kept having to go into the "change source control" and re-bind the solution. After a while, this began to get annoying. Then I found this post: http://www.eggheadcafe.com/software/aspnet/33487526/connecting-automatically.aspx. It turned out the solution was to set some registry keys. I navigated to HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0\TeamFoundation\Servers\ and changed "Offline" to 0 and "AutoReconnect" to 1. I've no idea how these got reset! (Please back-up your registry first if you want to try the same.)

System.ArgumentException: Illegal characters in path

This exception caused me a headache for an hour today on a development web site. After various rebuilds failed to cure the issue, I found out that the aspnet_wp.exe process had somehow become corrupted. Re-saves of the web.config file didn't help, so I opened Task Manager, killed the process and was back up and working again.

Get a list of all Sitecore Items tagged with specific multilist items

If you wish to return all items in the content tree that have been tagged with a specific multilist item, you might be tempted to use Sitecore.Context.Database.SelectSingleItem(), passing it an XPath query. The problem with this is that performance degrades as the content tree grows. A far more efficient way is to use the GetReferrers method of the LinkDatabase class as shown below:

Database db = Sitecore.Context.ContentDatabase;

LinkDatabase linkDb = Globals.LinkDatabase;

// lookupItem is the multilist item
ItemLink[] links = linkDb.GetReferrers( lookupItem );

foreach( ItemLink link in links )
{
  Item linkedItem = db.Items[link.SourceItemID];
  // Process item...
}

Example Useful C# Extension Functions

Here are a few extension functions that I find useful:

        public static bool IsNullOrEmpty(
        this string expression )
        {
            bool result = string.IsNullOrEmpty(
            expression );
            return result;
        }

        public static string ToFormat(
        this string expression, params object[] args )
        {
            string result = String.Format(
            expression, args );
            return result;
        }

        public static bool IsValidEmailAddress(
        this string expression )
        {
            bool result = BaseRegexHelper.IsValid(
            expression, emailRegex );
            return result;
        }

        public static bool IsValidGuid(
        this string expression )
        {
            bool result = BaseRegexHelper.IsValid(
            expression, guidRegex );
            return result;
        }

The latter two functions call this method:

        public static bool IsValid(
        string input, string pattern )
        {
            bool isValid = false;

            if( input != null )
            {
                string trimmedExpression =
                input.Trim();

                if( trimmedExpression.Length > 0 )
                {
                    Regex regexGuid = new Regex(
                    pattern, RegexOptions.IgnoreCase );
                    isValid = regexGuid.IsMatch(
                    trimmedExpression );
                }
            }

            return isValid;
        }

Write to Sitecore log file from XSLT

It is simple to write to the Sitecore log file from within an XSLT file without having to write any custom code. We can just hook up to the Sitecore.Diagnostics.Log class and call one of its methods.

In the web.config, define the extension under <xslextensions>:

<extension mode="on"
type="Sitecore.Diagnostics.Log, Sitecore.Kernel"
namespace="http://www.sitecore.net/log"
singleInstance="true" />

Within the XSLT file, add a prefix that matches the namespace you used in the above step:

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:sc="http://www.sitecore.net/scReal"
xmlns:dot="http://www.sitecore.net/dot"
xmlns:log="http://www.sitecore.net/log"
exclude-result-prefixes="dot sc log">

The Log class contains a number of overloads for Info, Warn, Error and so on. Some of these expect an exception as a parameter, so we cannot call these direct from XSLT. We can, however match the overloads that expect a string and an object (eg. Warn( String, Object )):

<xsl:value-of select="log:Warn('Warning message', 'Another string... perhaps the name of your rendering file')" />

That's it! Now you can log whatever you like from within your renderings.

Using Linq lambda expressions to retrieve XML elements based on the value of an attribute

The following example program loads an XML file, then selects all the elements named "field" within it. It then uses a lambda expression to get the inner text of the "alternativeTitle" element.

class Program
{
static void Main( string[] args )
{
XDocument xd = XDocument.Load( "..\\..\\file.xml" );

var fields = from el in xd.Descendants()
where el.Name.ToString().StartsWith( "field" )
select el;

Console.WriteLine( GetElementValue(fields, "alternativeTitle") );
Console.ReadLine();
}

static string GetElementValue( IEnumerable<XElement> elements, string attributeName )
{
return elements.Single( p => p.Attributes().Single( q => q.Name == "name" ).Value == attributeName ).Value;
}
}

The XML file used in the example is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<add>
<doc>
<field name="id">some_id</field>
<field name="readableid">interesting_publications</field>
<field name="name">Interesting Publications</field>
<field name="alternativeTitle">Online publications</field>
</doc>
</add>

The program outputs the text:

Online publications

Enable XSLT IntelliSense within Visual Studio

Wouldn't it be nice to have Visual Studio list the available template names when typing out a call-template statement in XSLT? Wouldn't it also be nice to have it list available parameter names when typing out a with-param statement?

To enable these autocompletions and more, you need to back up your registry and then run regedit. Within regedit, create a string value called "XsltIntellisense" under "HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0\XmlEditor" key, giving it the value "True". That's it!

Ultimately, I'd like to see full IntelliSense for XSLT in Visual Studio, but this is a good start.