ReturnValue1.cs

// One solution is to pass a default value into the method.
string uri = configFile.GetValueOrDefault(“serviceUri”, 
                                          “http://example.com/service");
ConnectToService(uri);

// Another possibility is to introduce a Maybe type to hold the return value.
Maybe<string> uri = configFile.GetValue(“serviceUri”); 
if(uri.HasValue)
{
    ConnectToService(uri.HasValue ? 
                     uri.Value : 
                     “http://example.com/service"); 
}
 
// If a missing return value is highly unlikely or 
// there can be no default handling of a missing value, 
// an exception can be thrown.
try
{
    ConnectToService(configFile.GetValue(“serviceUri”)); 
}
catch(MissingConfigurationException exception)
{
    // handle the error
}