Microsoft has apparently added Guid.TryParse() to .NET 4.0, but if you're stuck using an older version of the framework, you're still kind of left flapping out in the wind.  Luckily, the great minds of the world have converged upon StackOverflow.com and provided a solution: call the Win32 function CLSIDFromString.

I have taken the code and created a little helper class with one public static method called TryParse.  Its usage is just like that of any other TryParse() method in the .NET Framework today.  Here is the code:

using System;
using System.Runtime.InteropServices;


/// <summary>
/// Class that encapsulates the Win32 function CLSIDFromString.
/// </summary>
public static class GuidHelper
{
    /// <summary>
    /// Converts the string representation of a GUID to its System.Guid equivalent.  A return value 
    /// indicates whether the conversion succeeded.
    /// </summary>
    /// <param name="s">A string containing the GUID to convert.</param>
    /// <param name="value">When this method returns, contains the System.Guid value equivalent to 
    /// the GUID contained in s, if the conversion succeeded, or Guid.Empty if the conversion 
    /// failed. The conversion fails if the s parameter is null or is not of the correct format.  
    /// This parameter is passed uninitialized.</param>
    /// <returns>true if s was converted successfully; otherwise, false.</returns>
    public static bool TryParse(string s, out Guid value)
    {
        if (string.IsNullOrEmpty(s))
        {
            value = Guid.Empty;
            return false;
        }


        // CLSIDFromString requires enclosing curly braces on its GUIDs.
        if (!s.StartsWith("{"))
        {
            s = "{" + s;
        }
        if (!s.EndsWith("}"))
        {
            s += "}";
        }


        int result = CLSIDFromString(s, out value);
        if (result >= 0)
        {
            return true;
        }
        else
        {
            value = Guid.Empty;
            return false;
        }
    }


    /// <summary>
    /// This function converts a string generated by the StringFromCLSID function back into the 
    /// original class identifier.
    /// </summary>
    /// <param name="sz">String that represents the class identifier</param>
    /// <param name="clsid">On return will contain the class identifier</param>
    /// <returns>
    /// Positive or zero if class identifier was obtained successfully
    /// Negative if the call failed
    /// </returns>
    [DllImport("ole32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, PreserveSig = true)]
    private static extern int CLSIDFromString(string sz, out Guid clsid);
}

Fair warning: I verified the author's performance numbers, but I have not yet run this through a profiler or done any checking for memory leaks. Use it at your own risk.

I suppose since the original is licensed under the cc-wiki license with attribution required, this is, too.

Anyway, enjoy!

You may have run into this error while trying to develop a site that uses Integrated Windows Authentication on Windows Server 2008 R2 with IIS7.5.  I sure did, and I beat my head against the wall for a couple of hours trying to figure it out.

It turns out to be a security mechanism built into Windows, and the workaround is simple.  Just choose one of the two methods listed in this Microsoft KB article:

• KB #896861

You can find a more detailed explanation here:

• DisableLoopbackCheck & SharePoint: What every admin and developer should know.

Hope this saves you some time.

(h/t to this ServerFault.com question/answer: IE 8 Authentication Denied on local SharePoint Site)