fix code

Author: PatrickFarley

articles/ai-services/openai/includes/gpt-v-dotnet.md

@@ -100,10 +100,14 @@ To run the quickstart, follow these steps:
     
     var imageUrl = "YOUR_IMAGE_URL";
     
+    var textPart = ChatMessageContentPart.CreateTextPart("Describe this picture:");
+    var imgPart = ChatMessageContentPart.CreateImagePart(imageUrl); 
+
     var chatMessages = new List<ChatMessage>
     {
         new SystemChatMessage("You are a helpful assistant."),
-        new UserChatMessage($"Describe this picture: {imageUrl}")
+        new UserChatMessage(textPart, imgPart)
+
     };
         
     ChatCompletion chatCompletion = await chatClient.CompleteChatAsync(chatMessages);