RestSharp for C# (.NET): Complete Guide with Examples

What is RestSharp and why is it needed?

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RestSharp is a popular open-source library for the C# (.NET) language, designed to simplify working with RESTful APIs. It provides a convenient and intuitive interface for making HTTP requests (GET, POST, PUT, DELETE, PATCH, and others) and processing responses from web services.

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RestSharp solves several key tasks:

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• Code simplification: Instead of writing bulky code using HttpClient, RestSharp offers a concise fluent interface.
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• Automatic serialization/deserialization: The library automatically converts your C# objects to/from JSON/XML, eliminating manual work.
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• Convenient error handling: RestSharp provides clear classes for handling HTTP statuses and exceptions.
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• Authentication support: Built-in support for OAuth, Basic Auth, JWT, and other schemes.
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• File handling: Easy file upload and download.
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The library is actively used in .NET applications (ASP.NET Core, console applications, Xamarin, Unity) for integration with external services: social networks, payment systems, cloud platforms, etc.

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Installing RestSharp

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RestSharp is installed via the NuGet package manager. Choose one of the methods:

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Via Package Manager Console (Visual Studio):

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Install-Package RestSharp

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Via .NET CLI (command line):

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dotnet add package RestSharp

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Via NuGet interface (Visual Studio/Rider):

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Open Manage NuGet Packages → find RestSharp → install the latest stable version.

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After installation, add the using directive to your code:

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using RestSharp;

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Quick start: first request

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Let's make a simple GET request to a public API (JSONPlaceholder) and get a list of users.

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using RestSharp;\n\nvar client = new RestClient("https://jsonplaceholder.typicode.com");\nvar request = new RestRequest("/users", Method.Get);\n\nvar response = client.Execute(request);\n\nif (response.IsSuccessful)\n{\n    Console.WriteLine(response.Content); // Will output JSON string\n}\nelse\n{\n    Console.WriteLine($"Error: {response.StatusCode} - {response.ErrorMessage}");\n}

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This code creates a client, forms a GET request to the /users endpoint, and outputs the response to the console. Note: response.IsSuccessful checks that the response status is in the 200-299 range.

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Main methods and functions of RestSharp

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Below are the key library methods with descriptions, parameters, and examples.

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1. RestClient(string baseUrl) — Client constructor

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Description: Creates an HTTP client instance with a base URL. All subsequent requests will use this URL as the base.

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Parameters:

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• baseUrl (string) — the base API address (e.g., "https://api.example.com").
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Example:

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var client = new RestClient("https://api.github.com");

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2. RestRequest(string resource, Method method) — Creating a request

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Description: Forms an HTTP request to the specified resource with the given method (GET, POST, PUT, DELETE, etc.).

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Parameters:

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• resource (string) — the relative path to the resource (e.g., "/users").
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• method (Method) — the HTTP method from the Method enumeration (Get, Post, Put, Delete, Patch, Head, Options).
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Example:

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var request = new RestRequ