app.config for a class library

Solution 1:

You generally should not add an app.config file to a class library project; it won't be used without some painful bending and twisting on your part. It doesn't hurt the library project at all - it just won't do anything at all.

Instead, you configure the application which is using your library; so the configuration information required would go there. Each application that might use your library likely will have different requirements, so this actually makes logical sense, too.

Solution 2:

I don't know why this answer hasn't already been given:

Different callers of the same library will, in general, use different configurations. This implies that the configuration must reside in the executable application, and not in the class library.

You may create an app.config within the class library project. It will contain default configurations for items you create within the library. For instance, it will contain connection strings if you create an Entity Framework model within the class library.

However, these settings will not be used by the executable application calling the library. Instead, these settings may be copied from the library.dll.config file into the app.config or web.config of the caller, so that they may be changed to be specific to the caller, and to the environment into which the caller is deployed.

This is how it has been with .NET since Day 1.

Solution 3:

Jon, a lot of opinion has been given that didn't correctly answer your question.

I will give MY OPINION and then tell you how to do exactly what you asked for.

I see no reason why an assembly couldn't have its own config file. Why is the first level of atomicy (is that a real word?) be at the application level? Why not at the solution level? It's an arbitrary, best-guess decision and as such, an OPINION. If you were to write a logging library and wanted to include a configuration file for it, that would be used globally, why couldn't you hook into the built-in settings functionality? We've all done it ... tried to provide "powerful" functionality to other developers. How? By making assumptions that inherently translated to restrictions. That's exactly what MS did with the settings framework, so you do have to "fool it" a little.

To directly answer your question, simply add the configuration file manually (xml) and name it to match your library and to include the "config" extension. Example:

MyDomain.Mylibrary.dll.Config

Next, use the ConfigurationManager to load the file and access settings:

string assemblyPath = new Uri(Assembly.GetExecutingAssembly().CodeBase).AbsolutePath;
Configuration cfg = ConfigurationManager.OpenExeConfiguration(assemblyPath);
string result = cfg.AppSettings.Settings["TEST_SETTING"].Value;

Note that this fully supports the machine.config heierarchy, even though you've explicitly chosen the app config file. In other words, if the setting isn't there, it will resolve higher. Settings will also override machine.config entries.

Solution 4:

In fact, the class library you are implementing, is retrieving information from app.config inside the application that is consuming it, so, the most correct way to implement configuration for class libraries at .net in VS is to prepare app.config in the application to configure everything it consumes, like libraries configuration.

I have worked a little with log4net, and I found that the one who prepared the application always had a section for log4net configuration inside main app.config.

I hope you find this information useful.

See you, and post comments about the solution you found.

EDIT:

At the next link you have an app.config with the section for log4net:

http://weblogs.asp.net/tgraham/archive/2007/03/15/a-realistic-log4net-config.aspx

Solution 5:

If you want to configure your project logging using log4Net, while using a class library, There is no actual need of any config file. You can configure your log4net logger in a class and can use that class as library.

As log4net provides all the options to configure it.

Please find the code below.

public static void SetLogger(string pathName, string pattern)
        {
            Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();

            PatternLayout patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = pattern;
            patternLayout.ActivateOptions();

            RollingFileAppender roller = new RollingFileAppender();
            roller.AppendToFile = false;
            roller.File = pathName;
            roller.Layout = patternLayout;
            roller.MaxSizeRollBackups = 5;
            roller.MaximumFileSize = "1GB";
            roller.RollingStyle = RollingFileAppender.RollingMode.Size;
            roller.StaticLogFileName = true;
            roller.ActivateOptions();
            hierarchy.Root.AddAppender(roller);

            MemoryAppender memory = new MemoryAppender();
            memory.ActivateOptions();
            hierarchy.Root.AddAppender(memory);

            hierarchy.Root.Level = log4net.Core.Level.Info;
            hierarchy.Configured = true;
      }

Now instead of calling XmlConfigurator.Configure(new FileInfo("app.config")) you can directly call SetLogger with desired path and pattern to set the logger in Global.asax application start function.

And use the below code to log the error.

        public static void getLog(string className, string message)
        {
            log4net.ILog iLOG = LogManager.GetLogger(className);
            iLOG.Error(message);    // Info, Fatal, Warn, Debug
        }

By using following code you need not to write a single line neither in application web.config nor inside the app.config of library.