What Is App.Config in C#.Net - How to Use It

Using app.config in .Net Core

1. You can use Microsoft.Extensions.Configuration API with any .NET Core app, not only with ASP.NET Core app.
   Look into sample provided in the link, that shows how to read configs in the console app.

2. In most cases, the JSON source (read as .json file) is the most suitable config source.

   Note: don't be confused when someone says that config file should be appsettings.json. You can use any file name, that is suitable for you and file location may be different - there are no specific rules.

   But, as the real world is complicated, there are a lot of different configuration providers:

   • File formats (INI, JSON, and XML)
   • Command-line arguments
   • Environment variables

   and so on. You even could use/write a custom provider.

3. Actually, app.config configuration file was an XML file. So you can read settings from it using XML configuration provider (source on github, nuget link). But keep in mind, it will be used only as a configuration source - any logic how your app behaves should be implemented by you. Configuration Provider will not change 'settings' and set policies for your apps, but only read data from the file.

Reading settings from app.config or web.config in .NET

You'll need to add a reference to System.Configuration in your project's references folder.

You should definitely be using the ConfigurationManager over the obsolete ConfigurationSettings.

C# VS2013 How to use App.config in a console application after publish it

When you publish the application the app.config is transformed into an exe.config. Open up that file and make your edits.

If you installed this program with a click once installer the easiest way to find the file is to just run the app, open the task manager (CTRL-SHIFT-ESC), select the app and right-click|Open file location. You should then find the *.exe.config file in the same folder.

App.Config file in console application C#

You can add a reference to System.Configuration in your project and then:

using System.Configuration;

then

string sValue = ConfigurationManager.AppSettings["BatchFile"];

with an app.config file like this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
   <appSettings>
       <add key="BatchFile" value="blah.bat" />
   </appSettings>
</configuration>

When/How Does My .NET Application Use Its App.Config File?

does that code get generated/executed before my application's entry point?

Think of a config file just as a standard text file. If your application code doesn't read and do anything with it, nothing will happen. So basically when you define some section in the app.config file, there is some code in your application (either in the BCL or custom) that at some moment will read, parse and interpret the values.

So, let's consider the example of trace listeners. When you try to trace something in your code, the underlying Trace class will use the config system to check the values you have defined in app.config. This config system parses the XML only once and stores it as singleton in memory to avoid the overhead everytime. So, it's only the first time you try to trace something that the config file is parsed and on subsequent calls the values are directly read from memory.

C# App.config vs Settings File

App.config for desktop applications and Web.config for web applications are part of .NET configuration system. Primarily they are used to control .NET framework settings in respect to our application. These are such configuration settings as substitutions of versions of assemblies (section <assemblyBinding>), substitution of .NET framework version (<startup>) etc. (see msdn for the full app.config schema.) One section is dedicated for custom settings of application developers (<appSettings>). There is also a possibility to create custom sections. So, when we need to store settings we can either piggy-back on the app.config or create our own separate configuration files.

Here are pros and contras of using app.config:

1. Pro: There is already a standard API in .NET to read settings from appSettings section. If you only need just a couple of config settings, it is much easier to use this ready API than to develop and test your own class to read your config files. Also, app.config file is already included in VS project for you.

2. Pro: There is a standard hierarchy of machine.config/app.config. If you plan such settings that can be set machine-wide and overridden or left as-is for individual applications, you should use app.config.

3. Pro/Con: App.config is cached in run-time. If you anticipate updates of it while your application is running, you need to specifically request refresh of certain section of config file. For web.config the web app is automatically restarted when something is changed in the file. This is quite convenient.

4. Con: app.config is stored in the same directory as your .exe file. Normally it will be in a subfolder of C:\Program Files. This directory is extra protected in Windows 7 from writing. You need to be member of Administrators group to write there and if your UAC (User Access Control) level in Control Panel is not set to 0 (which normally is not), you will be asked by the OS to confirm writing to c:\Program Files. So, users without Administrator rights will not be able to change configuration in app.config. Same goes for changing your settings programmatically: your application will get exception when attempts to write app.config if it runs not under an admin user on Windows 7. Your own config files usually go to C:\ProgramData\ or c:\Users subfolder (on Windows 7). These locations are friendlier to writing by users or programs.

5. Con: If user edited your app.config file and accidentally corrupted it, the whole application will not start with some obscure error message. If your separate config file is corrupted, you will be able to provide more detailed error message.

In conclusion: app.config gives you easier (faster development) approach, mostly suitable for read-only settings. Custom settings file gives you more freedom (where to store file, validation/error handling, more flexibility with its schema) but requires more work during development.

Accessing app.config in ASP.NET

In ASP.NET applications, the default configuration file is named web.config. This is a convention you should probably stick to, that allows you to easily use the ConfigurationManager to access configuration settings.

I suggest having a look at http://en.wikipedia.org/wiki/Web.config as a starting point to learn the ins and outs of basic .NET application configuration in the ASP.NET domain.

You can link configuration files together, by setting the file attribute of configuration sections you want to override: http://www.codeproject.com/KB/dotnet/appsettings_fileattribute.aspx

---

Related Topics