This is what I tried now and this is working.

//Content is a byte array containing document data
BinaryData data = BinaryData.FromBytes(Content);

var analyzeOptions = new AnalyzeDocumentOptions(modelId, data) 
{ 
  Pages = "1-2", 
  Features = { DocumentAnalysisFeature.QueryFields }, 
  QueryFields = { "FullName", "CompanyName", "JobTitle" } 
};

Operation<AnalyzeResult> operation = await client.AnalyzeDocumentAsync(WaitUntil.Completed, analyzeOptions);

AnalyzeResult result = operation.Value;