You should build csharp api first, it will generate a nuget package, or you can download our prebuit package. You may refer to [this](https://stackoverflow.com/a/55167481) on how to install local nuget package.
And don't forget to install backend dependencies. Take tensorrt backend as example, you have to install cudatoolkit, cudnn and tensorrt. The version of backend dependencies that our prebuit nuget package used will be offered in release note.
You can either convert your model according to this [tutorial](../../docs/en/tutorials/how_to_convert_model.md) or download the test models from [OneDrive](https://1drv.ms/u/s!Aqis6w3rjKXSh2dXZ5OqbZIZSu9P?e=nefSdY) or [BaiduYun](https://pan.baidu.com/s/1VJkLo2oqHos6ZWDT7xamFg?pwd=STAR). The web drive contains onnx and tensorrt models and the test models are converted under environment of cuda11.1 + cudnn8.2.1 + tensorrt 8.2.3.0 + GTX2070s.