Mastering ChatGPT and OpenAI APIs with C#

Learn how to integrate OpenAI APIs into real C# applications using both direct HTTP requests and OpenAI's official .NET library.

Most Generative AI tutorials are built around Python. But if you are already a C# developer, you should not have to switch languages just to understand how modern AI APIs work.

This course takes a hands-on, C#-first approach.

Instead of hiding everything behind a framework, we begin by working directly with the OpenAI API so you can understand what is actually being sent in a request and returned in a response. We then move to OpenAI's official .NET library and build progressively more capable applications using streaming responses, Tool Calls, multiple tools, and image generation.

Throughout the course, you will build working Blazor applications and see how the individual API concepts fit together in a real application.

What You Will Learn

You will learn how to:

• Understand the relationship between GPT models, ChatGPT, and the OpenAI API

• Set up an OpenAI account and securely use an API key

• Call OpenAI APIs directly from C# using HttpClient

• Understand the structure of chat requests and responses

• Process responses using both non-streaming and streaming workflows

• Work with system messages, API options, finish reasons, and token usage

• Use OpenAI's official .NET library in C# applications

• Build asynchronous and streaming chat experiences

• Extend a model with your own C# functions through Tool Calls

• Register and orchestrate multiple tools in the same application

• Let the model decide when external tools should be invoked

• Generate images using the OpenAI Image API

• Configure image generation options such as image size and quality

• Save generated images and make them available to your application

• Combine Chat Completion Tool Calls with image generation

• Generate multiple independent images from a single user request

• Integrate OpenAI capabilities into interactive Blazor Web Apps

Learn the API, Not Just the Syntax

One of the goals of this course is to help you understand what happens behind the code.

You will first work with the API more directly so you can see the request and response structures yourself. After that foundation is established, we move to OpenAI's official .NET library and see how the SDK represents those same concepts through strongly typed C# classes.

This makes it easier to understand not only how to write the code, but also why the code works.

Build with OpenAI's Official .NET Library

The second half of the course focuses on practical development using the official OpenAI .NET library.

You will work with chat completions, streaming responses, Tool Calls, multiple tools, and image-generation workflows while progressively extending the same application.

Rather than treating these capabilities as isolated examples, the course demonstrates how they can work together inside a real C# application.

Go Beyond Chat with Tool Calls

A language model becomes much more useful when it can interact with functionality outside the model itself.

You will learn how to expose your own C# functions as tools, allow the model to decide when those tools are needed, process tool-call arguments, return results to the model, and coordinate multiple tools within the same request.

The course also demonstrates how a chat model can trigger an image-generation tool, combining conversational reasoning with the OpenAI Image API.

Generate Images with the OpenAI Image API

The image-generation section has been rebuilt around the current GPT Image workflow.

You will generate images from text prompts, configure image-generation options, save generated image data to local files, display the results in a Blazor application, and provide progress feedback while longer image requests are running.

You will then take the workflow one step further by connecting image generation to Tool Calls and generating multiple independent images from a single natural-language request.

Earlier OpenAI image-generation lessons are retained separately as a legacy archive for students who want to compare previous workflows with the updated implementation.

Hands-On Blazor Projects

This is not a slide-only course.

You will build and modify working C# applications throughout the course, including interactive Blazor Web Apps that communicate with OpenAI APIs, stream model responses, execute tools, and display generated images.

The examples are intentionally developed step by step so you can understand how each capability is added to the application.

Who Is This Course For?

This course is designed for:

• C# developers who want to start building applications with Generative AI

• .NET developers who want practical experience with the OpenAI API

• Developers who want to understand both direct REST API access and the official OpenAI .NET library

• Engineers interested in streaming responses, Tool Calls, and AI-powered application workflows

• Blazor developers who want to integrate OpenAI capabilities into web applications

• Developers coming from traditional application development who want a practical path into Generative AI

You do not need Python experience.

Prerequisites

You should have:

• Enthusiasm for learning Generative AI development with C#

• Basic knowledge of C# programming

Experience with ASP.NET Core or Blazor is helpful, but not required to understand the OpenAI API concepts covered in the course.

A Practical Foundation for Building AI Applications with C#

OpenAI's APIs and models continue to evolve, but the fundamental application patterns remain important: sending structured requests, processing responses, streaming output, calling external tools, and integrating generated content into your own application.

This course focuses on those practical foundations and shows how to implement them using C# and the .NET ecosystem.

If you are ready to move beyond simply using ChatGPT and start building your own AI-powered applications, let's get started.