functioncalling.cs

   if (completion.FinishReason == ChatFinishReason.ToolCalls)
   {
       try
       {
           var toolResult = string.Empty;
           foreach (var toolCall in completion.ToolCalls)
           {
               switch (toolCall.FunctionName)
               {
                 case "GetImageDataAsync":
                 {
                     // gets the function argument in this case imageLink variable that is the url from the prompt
                     var arguments = JsonSerializer.Deserialize<GetImageArguments>(toolCall.FunctionArguments);
                     
                     // this will get us the image data consisting of binary data and content type
                     var imageResponse = await _functions.GetImageDataAsync(arguments.imageLink);

                     if (imageResponse == null)
                     {
                         toolResult = "No image found";
                     }
                     else
                     {
                         // the special code here is  ChatMessageContentPart.CreateImageMessageContentPart that allows us to add image or another modality to our prompt :) 
                         var promptUserMessage = ChatMessageContentPart.CreateTextMessageContentPart($"Given this image and these image requirements: {context} can you tell me if its a valid loft insulation evidence");
                         var imageUserMessage = ChatMessageContentPart.CreateImageMessageContentPart(imageResponse.BinaryData, imageResponse.ContentType);

                         // Add the imageBytes as a new input message
                         inputMessages.Clear();
                         inputMessages.Add(new UserChatMessage(promptUserMessage));
                         inputMessages.Add(new UserChatMessage(imageUserMessage));

                         // Now, make a final call with the updated input messages
                         ChatCompletion finalCompletion = await chatClient.CompleteChatAsync(inputMessages, chatCompletionOptions);

                         // Process the final response
                         // toolResult will have the final result here that the client will display 
                         toolResult = finalCompletion.Content[0].Text;
                         // record token usages for costing purposes
                         var properties = new Dictionary<string, string>
                         {
                             { "TotalTokens", finalCompletion.Usage?.TotalTokens.ToString() },
                             { "PromptTokens", finalCompletion.Usage?.InputTokens.ToString() },
                             { "CompletionTokens", finalCompletion.Usage?.OutputTokens.ToString() },
                         };

                         _telemetryClient.TrackMetric("AzureOpenAIApiResponseTotalTokens", finalCompletion?.Usage?.TotalTokens ?? 0, properties);
                     }
                 }
                 break;
               }
           }
       }
  }