According to the documentation, both Onnx and Json paths are optional. Make at least Onnx path mandatory for conversion.
https://github.com/dotnet/machinelearning/blob/master/src/Microsoft.ML/Models/OnnxConverter.cs
OnnxConverterconverter=newOnnxConverter(){InputsToDrop=new[]{"Label"},OutputsToDrop=new[]{"Label","Features"},Onnx=onnxPath,Json=onnxAsJsonPath,Domain="Onnx"};converter.Convert(model);
According to the documentation, both
OnnxandJsonpaths are optional. Make at leastOnnxpath mandatory for conversion.https://github.com/dotnet/machinelearning/blob/master/src/Microsoft.ML/Models/OnnxConverter.cs