Using 32-bit DLLs on a 64-bit machine exposed to a .NET Web Application via COM+

I recently had some challenges calling 32-bit DLLs from a third party from a ASP.NET Web Application via COM+ on a 64-bit machine running Windows Server 2008. The 3rd party DLLs also required an ODBC connection to the database.

Issue 1 - Exception: Retrieving the COM class factory for component with CLSID {XXXX} failed due to the following error: 80040154.

I'd registered the DLLs in Windows\sysWOW64 using the version of regsrv32 in that folder.

Calls to the third party DLL worked from unit tests in Visual Studio but failed from the Web Application hosted in IIS on the same machine with the 80040154 error.

Changing the application pool to "Enable 32-Bit Applications" ([enable32BitAppOnWin64]) resolved the issue.

Issue 2 - The ODBC connection was not available

I'd created the ODBC connectino using %SystemRoot%\system32\odbcad32.exe. Again, this worked fine for the VS unit tests but fell over when run from IIS.

Using odbccad32.exe from the sysWOW32 folder to create the ODBC connection resolved the issue.

Issue 3 - Calling the 32-bit COM class from the WCFTestClient.exe resulted in the 80040154 (Class not registered) exception again

Wcftestclient.exe will need to be flagged to run in as 32-bit by using the CorFlags.exe tool. E.g.

corflags.exe /32BIT+ wcftestclient.exe

See also:

• Flipping bits on managed images to make them load with the right bitness...
• Debugging WCF service with x86 dependencies on a x64 bit machine

LINQ To SQL - "String must be exactly one character long.."

I used LINQ to SQL to throw together a quick data access layer to a third party database. In theory in will only be a temporary measure.

When trying to retrieve a record I got the following error:

System.FormatException: String must be exactly one character long..
System.Convert.ToChar(String value, IFormatProvider provider)
System.String.System.IConvertible.ToChar(IFormatProvider provider)
System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
System.Data.Linq.DBConvert.ChangeType(Object value, Type type)
Read_Name(ObjectMaterializer`1 )
MoveNext()
...

Turns out the issue is related to a VarChar(1) NOT NULL column on the table. The Code Generation has interpreted this as char (System.Char). Changing this to string (System.String) got the system going again. There is some risk now of assigning a value longer than one charater but I can live with that for a temporary solution.

Firing an ASP.NET postback for a control on page load

The following can be used to automatically fire the post back event from an ASP.NET control when the page is done loading client side. Using ClientScript.GetPostBackEventReference() avoids the need to manually create the __doPostBack script using the controls client id.

    string triggerScript = ClientScript.GetPostBackEventReference(this.btnRefreshData, string.Empty);
    Page.ClientScript.RegisterStartupScript(this.GetType(), "PostbackControlScript", triggerScript, true);

If using an UpdatePanel with partial postback use the following instead:

    string triggerScript = ClientScript.GetPostBackEventReference(this.btnRefreshData, string.Empty);
    if(ScriptManager.GetCurrent(Page).IsInAsyncPostBack)
    {
        ScriptManager.RegisterStartupScript(this.btnRefreshData, this.GetType(), "PostbackControlScriptUpdate", triggerScript, true);
    }
    else
    {
        Page.ClientScript.RegisterStartupScript(this.GetType(), "PostbackControlScript", triggerScript, true);

IE8 security warning when mixing http and https content

Ran into an issue with IE8 showing the following prompt with every page view under SSL.

Security Warning
Do you want to view only the webpage content that was delivered securely?
This webpage contains content that will not be delivered using a secure HTTPS
connection, which could compromise the security of the entire webpage.

Turns out the addition of the Microsoft AJAX CDN service is the cause in this particular case. Changing the script link to use SSL resolves the issue.

Programmatic log4net configuration at runtime

I've been looking for a way to enable/disable a log4net appender at runtime through code. Doing so would remove the need to remote to the production web server to alter the logging config file.

The blog post Tweaking log4net Settings Programmatically has a extension method to perform actions on certain types of appender.

Visual Studio 2010 CSS colour picker

Came across a Colour picker dialog for use when editing CSS files in the Visual Studio 2010 editor.

Right click on the style and select Build Style or
Styles (Menu) > Build Style

Disabling a Trigger for a LINQ to SQL DataContext

I have a trigger on a table that fires on updates and adds a record to another table indicating that it needs to be rolled up to an external system. In a few cases I need to dynamically suppress this trigger to prevent circular updates between the two systems. My data access is via LINQ to SQL for the system in question.

The article Disabling a Trigger for a Specific SQL Statement or Session deals with the same problem.

using(DbDataContext dc = new DbDataContext())
{
 //Update fields etc...

 dc.Connection.Open();
 //Set the context_info here within the open connection so that it is in-scope 
 //for the triggers
 dc.ExecuteCommand("SET Context_Info 0x55555");
 dc.SubmitChanges();
 dc.Connection.Close();
}

 CREATE TRIGGER TR_Mock ON dbo.TableForTrigger FOR UPDATE
 AS 
 DECLARE @Cinfo VARBINARY(128) 
 SELECT @Cinfo = Context_Info() 
 IF @Cinfo = 0x55555 
 RETURN 
 PRINT 'Trigger Executed' 
 -- Actual code goes here
GO  

See Also:

• Stack Overflow: Why is my CONTEXT_INFO() empty?