Simplest way to have a configuration file in a Windows Forms C# application

Question

You want to use an App.Config.

When you add a new item to a project there is something called Applications Configuration file. Add that.

Then you add keys in the configuration/appsettings section

Like:

<configuration>
 <appSettings>
  <add key="MyKey" value="false"/>

Access the members by doing

System.Configuration.ConfigurationSettings.AppSettings["MyKey"];

This works in .NET 2 and above.

Clarification of previous answers...

1. Add a new file to your project (Add → New Item → Application Configuration File)

2. The new configuration file will appear in Solution Explorer as App.Config.

3. Add your settings into this file using the following as a template

   <configuration>
     <appSettings>
       <add key="setting1" value="key"/>
     </appSettings>
     <connectionStrings>
       <add name="prod" connectionString="YourConnectionString"/>
     </connectionStrings>
   </configuration>
   

4. Retrieve them like this:

   private void Form1_Load(object sender, EventArgs e)
   {
       string setting = ConfigurationManager.AppSettings["setting1"];
       string conn = ConfigurationManager.ConnectionStrings["prod"].ConnectionString;
   }
   

5. When built, your output folder will contain a file called <assemblyname>.exe.config. This will be a copy of the App.Config file. No further work should need to be done by the developer to create this file.

From a quick read of the previous answers, they look correct, but it doesn't look like anyone mentioned the new configuration facilities in Visual Studio 2008. It still uses app.config (copied at compile time to YourAppName.exe.config), but there is a UI widget to set properties and specify their types. Double-click Settings.settings in your project's "Properties" folder.

The best part is that accessing this property from code is typesafe - the compiler will catch obvious mistakes like mistyping the property name. For example, a property called MyConnectionString in app.config would be accessed like:

string s = Properties.Settings.Default.MyConnectionString;

You should create an App.config file (very similar to web.config).

You should right click on your project, add new item, and choose new "Application Configuration File".

Ensure that you add using System.Configuration in your project.

Then you can add values to it:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="setting1" value="key"/>
  </appSettings>
  <connectionStrings>
    <add name="prod" connectionString="YourConnectionString"/>
  </connectionStrings>
</configuration>

---

    private void Form1_Load(object sender, EventArgs e)
    {
        string setting = ConfigurationManager.AppSettings["setting1"];
        string conn = ConfigurationManager.ConnectionStrings["prod"].ConnectionString;
    }

---

Just a note: According to Microsoft, you should use ConfigurationManager instead of ConfigurationSettings (see the remarks section):

"The ConfigurationSettings class provides backward compatibility only. For new applications you should use the ConfigurationManager class or WebConfigurationManager class instead. "

The default name for a configuration file is [yourexe].exe.config. So notepad.exe will have a configuration file named notepad.exe.config, in the same folder as the program. This is a general configuration file for all aspects of the CLR and Framework, but it can contain your own settings under an <appSettings> node.

The <appSettings> element creates a collection of name-value pairs which can be accessed as System.Configuration.ConfigurationSettings.AppSettings. There is no way to save changes back to the configuration file, however.

It is also possible to add your own custom elements to a configuration file - for example, to define a structured setting - by creating a class that implements IConfigurationSectionHandler and adding it to the <configSections> element of the configuration file. You can then access it by calling ConfigurationSettings.GetConfig.

.NET 2.0 adds a new class, System.Configuration.ConfigurationManager, which supports multiple files, with per-user overrides of per-system data. It also supports saving modified configurations back to settings files.

Visual Studio creates a file called App.config, which it copies to the EXE folder, with the correct name, when the project is built.

The best (IMHO) article about .NET Application configuration is on CodeProject, Unraveling the Mysteries of .NET 2.0 Configuration. And my next favorite (shorter) article about sections in the .NET configuration files is Understanding Section Handlers - App.config File.