Using App.Config for user defined runtime parameters

September 27, 2007

These are the steps involved in defining runtime parameters and using them in your code.

1. Create a App.Config file
2. Define the runtime parameters and provide values for these
3. Access these parameters in your code
4. Verify changing the parameter value at runtime affects the application

Step 1: Create App.Config file

1a. Create a Console Application
1b. In Solution Explorer, right click on project. Add->New Item. Select Application Configuration file. This file will be added to your project.

Step 2: Define the runtime parameters and provide values for these

2a. Open App.Config.
2b. Define the keys and values for your runtime parameters.

Example:

<configuration>
<appSettings>
<add key="OperatorName" value="Rita"></add>
<add key="LoggerLevel" value="5"></add>
</appSettings>
</configuration>

You can define any key and provide values. Ensure you don’t have duplicate keys.

Step 3: Access these parameters in your code

3a. Add a refernce System.Configuration DLL.¹
3b. Add the following lines in your code. You can directly add these lines in Main.

string name = System.Configuration.ConfigurationManager.AppSettings["OperatorName"];
Console.Writeline("Welcome " + name);
string level = System.Configuration.ConfigurationManager.AppSettings["LoggerLevel"];
Console.Writeline("Logger level: " + level);

3c. Build your project and execute it.The output should be:

Welcome Rita
Logger level: 5

Step 4: Verify changing the parameter value at runtime affects the application

4a. When you build your project, the App.Config file is copied to your Debug/Release folder with the name .exe.config. My project is named UseAppConfig. The App.Config in my Debug folder is UseAppConfig.exe.config

Open the .config file in your working directory (Debug/Release). Change the values to Mary and 1. In the same folder you will see your executbale. Double click on this and you should see the new values.²

You are all set. You can identify all those parameters that make sense as runtime parameters, define a meaningful key for each parameter and start using it. You no longer have to build your application every time you want to change the parameter value.

Notes

1: You need this reference only if you are using .NET  2.0
2: If you change the App.Config from Visual Studio IDE, then you need to rebuild your project to see the new values.