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Configuring log4net with VS2010 and .Net 4.0

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And now on to our article…

After spending a few hours this morning trying to get log4net working with a project, I decided to share my findings.   I chased a lot of dead-ends for what wound up being a fairly simple solution.  Here is a quick article to save both myself, and maybe you, some time in the future.

Get Log4Net

Go to and get the latest version.    Add the project file to your solution.   Then right-click that project, choose the build tab and…

Step 1: Set the log4net conditional compilation symbols replacing NET_1_0 with NET_4_0.

Log4Net Requires Full .Net Access

That means you cannot use “client profile”.  log4net was originally written to log web services.  As such it expects to have a lot of server-side classes available, even though most of those classes are never instantiated.

Step 2: Build  Your Application & The Log4Net component under .Net 4.0, not .Net 4.0 Client Profile

Make Log4Net Less Secure

The .Net 4.0 assemblies are more secure by default.  You need to override this.   As I’m not a .Net development guru I’m not really certain what the differences mean, but Google is your friend (and mine) here, so if you are concerned (and you should be before launching a public app) then search the Internet to find out what this mean. In the meantime…

Step 3: Make log4net assembly less secure, add
[assembly: System.Security.SecurityRules(System.Security.SecurityRuleSet.Level1)]
to the log4net AssemblyInfo.cs file.


That’s it, the first steps for getting a log4net component into your application.   Now you can follow some of the development & deployment document on the Apache site: