Scott Hanselman

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The Backstory: I was thinking since the NuGet .NET package management site is starting to fill up that I should start looking for gems (no pun intended) in there. You know, really useful stuff that folks might otherwise not find. I'll look for mostly open source projects, ones I think are really useful. I'll look at how they built their NuGet packages, if there's anything interesting about the way the designed the out of the box experience (and anything they could do to make it better) as well as what the package itself does.

This week's Package of the Week is "ELMAH 1.2 with SQL Compact."

You may already use ELMAH. Don't stop reading now, because you're going to need this information!

Now, I've been blogging and promoting ELMAH (Error Logging Modules and Handlers) for years. It's the first thing I add to any ASP.NET project of any importance. It's one of the great little gems of ASP.NET open source.

I've shown "install-package elmah" in a number of talks and videos as my go-to demo for how NuGet and a well structured OSS package get you started quickly. Recently the ELMAH team has started to do some restructuring of their packages, and I wanted to showcase their work so you can not only learn from it, but also implement similar structures in your own packages.

First, spend a few minutes checking out how ELMAH works and how it can add to your ASP.NET project. Now, let's look at the (currently three, soon to be more) ELMAH packages that are up on NuGet.org.

There's currently:

• ELMAH Core Library (no config) - "Core library for ELMAH (Error Logging Modules and Handlers) without any configuration"
  • This one includes just the library. If you already have a custom ELMAH configuration or you want to create a new one, you can use and depend on this "core" package.
• ELMAH - "ELMAH with initial configuration for getting started quickly. ELMAH (Error Logging Modules and Handlers) is an application-wide error logging facility that is completely pluggable. It can be dynamically added to a running ASP.NET web application, or even all ASP.NET web applications on a machine, without any need for re-compilation or re-deployment."
  • This one includes the basics you'll need to for a drop-in/just-works configuration. This isn't the "core" library, but rather one that depends on the core. It's the "getting started" one.
• ELMAH on MS SQL Server Compact - "ELMAH with configuration for getting started quickly on a Microsoft SQL Server Compact database as the error log."
  • This package depends on the Elmah library and Elmah.CoreLibrary package as well as SqlServerCompact and adds configuration for using them together.
  • Dependency chain: elmah.sqlservercompact -> elmah -> elmah.corelibrary

Here's the web.config.transform that elmah.sqlservercompact adds to your base ELMAH web.config:

<configuration>
  <elmah>  
    <errorLogtype="Elmah.SqlServerCompactErrorLog, Elmah"connectionStringName="elmah-sqlservercompact"/>
  </elmah>
  <connectionStrings>    
    <addname="elmah-sqlservercompact"connectionString="Data Source=|DataDirectory|\Elmah.sdf"/>
  </connectionStrings>
</configuration>

Give it a try, it's easy, just install-package elmah.sqlservercompact. This basic package dependency structure will enable the Elmah guys to create "quick starts" with different configurations that each depend on elmah, which depends on the elmah.corelibrary. 

ELMAH supports many formats for storing errors, but I think that SQL Server Compact is a great choice for small to medium size applications.

• Everything in one place and queryable.
• No mess of text files or XML files
• Database survives application restarts/recycles

If you're using a WebFarm, you might want to use a central SQL Server instance, but I know a number of folks who run WebFarms and still prefer their errors on a per WebServer basis.

When your application starts up, ELMAH will put the Elmah.sdf in your ~\App_Data folder. The database is structured like this image at right. With the SQL Server Compact tooling that's added with Visual Studio 2010 SP1 you can open the SDF file right in VS and query it if you like.

If you prefer a different backend for your logs, we should soon see NuGet "quick start" packages for many of the supported ELMAH storage solutions. You can even get your errors as RSS or JSON!

• Microsoft SQL Server
• Oracle (OracleErrorLog)
• SQLite (version 3) database file
• Microsoft Access (AccessErrorLog)
• Loose XML files
• RAM (in-memory)
• SQL Server Compact Edition
• MySQL
• PostgreSQL

Also, be aware that Elmah has just be updated to version 1.2 with a number of new features and fixes. ELMAH works in .NET 1.1 and .NET 2, so there's no excuse for not checking it out!

Enjoy, and thanks to the ELMAH team for putting up with my nagging, bug reports and reviews over the last few months! It's only because I love the project so much!

Related Links

• ELMAH: Error Logging Modules and Handlers for ASP.NET (and MVC too!)
• ELMAH and Exception Driven Development FTW
• Good Exception Management Rules of Thumb - Back to Basics Edition
• Other blog posts in the NuGet Package of the Week category

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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