These .NET and C APIs are not available anymore as part of Simulink Real-Time. The reason is that Simulink Real-Time went through a major product update for the R2020b release, and the .NET and C APIs for Simulink Real-Time were deprecated in R2020b as part of this.
Consider one of the following alternative workflows:
(1) MATLAB App Designer:
Starting from R2020b, the recommended way to control applications on Speedgoat is through MATLAB App Designer. The .NET API had a limited number of functions, while with App Designer, you have access to the full MATLAB API for Simulink Real-Time. For an example, see:
Starting from R2021b, if you have a MATLAB Compiler license, you can compile your App Designer GUI as a standalone executable (to run in on a computer without a MATLAB installation/license). For more information, see:
(2) MATLAB Engine API
You can still design your GUI in C# and other languages such as Python by using the MATLAB External Language Interfaces, which can call the MATLAB API for Simulink Real-Time:
This workflow requires MATLAB and Simulink Real-Time on the host computer (this is a new license model introduced with R2020b: Simulink, MATLAB Coder and Simulink Coder are no longer required if you don't need to modify/build real-time applications).
(3) Simulink Real-Time ASAM XIL API:
Starting from R2021b, if your goal is automatic testing, you can interface Simulink Real-Time models with test cases from third-party software that supports the ASAM XIL API (e.g. TraceTronic ECU-TEST or Piketec TPT). To use an ASAM XIL simulation workflow for your real-time applications, install the Simulink Real-Time XIL API support package. Follow the workflow in:
The Simulink Real-Time XIL API support package provides an API that lets you use a C# program to control real-time applications on the target computer. For more information, see: