Application Level - app.config

This is application specific and should be considered a "read-only" file
This contains settings specific to the application

<appSettings>

You can read and write these settings.
There is no type checking
They do not have user scope
They cannot be accessed and maintained from the (Project > Properties > Settings) dialog box.

<configuration> 
  <appSettings> 
    <add key="Timeout" value="400"/> 
  </appSettings> 
</configuration> 

System.Configuration.ConfigurationManager.AppSettings["TimeOut"]; 
System.Configuration.ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None) 

<applicationSettings>

These are read only settings
There is type checking
They can be accessed and maintained from the (Project > Properties > Settings) dialog box.

<configuration> 
  <applicationSettings> 
    <ProjectName.Properties.Settings> 
      <Setting name="TimeOut" serializeAs="String"> 
        <value>"400"</value> 
      </Setting> 
    </ProjectName.Properties.Settings> 
  </applicationSettings> 
</configuration> 

System.Configuration.ConfigurationManager.AppSettings["TimeOut"]; 
System.Configuration.ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None) 
Properties.Settings.Default 

If you want to persist the changes call the Save method.

Properties.Settings.Default.Save 

Properties.Settings.Default.Properties["TimeOut"] 

This appears as app.config in your IDE and is then automatically renamed when the project is built.
Application settings allow you to store and retrieve settings and other information dynamically

Exact FileName

The name of this file depends on the type of application.

• Executables / Addins - file name is "nameofapplication".config

Web Services