You have several options according to the "needs"
Of course you have the form by code, there we are helped by the class ConfigurationManager inside the namespaces System.configuration
Example if we have
<appSettings>
<add key="ForceSide" value="DarkSide"/>
</appSettings>
To get its value
ForceSide.Text = ConfigurationManager.AppSettings["ForceSide"];
For the full name with namespaces
ForceSide.Text = System.Configuration.ConfigurationManager.AppSettings["ForceSide"];
You can also read it directly on webcontrols with what is called ASP.NET Expressions
Example in a literal ...
<asp:Literal ID="ForceSide2" Text="<%$ AppSettings: ForceSide %>" runat="server" />
NOTE: Remember that it starts with the $ sign (which we usually place =) ..Text=" <% $ AppSettings:
Links that can help you: