The Open Client .NET OpenAPI is a generic set of .NET classes that can be used instead of the generated .NET proxies produced by ProxyGen. Without proxies, you must do all of the setup work in your client code to an access application service on the application server. You must know the procedure names, including relative path information (for the equivalent ABL RUN statement), the number of parameters along with their type, and the return type for user-defined functions. When using the OpenAPI, there is no compile time checking so all function prototype error checking is done at run time.