Nswag C# (How It Works For Developers)

How to Use NSwag in C#

1. Create a RESTful web API using Swagger UI.
2. Create a C# console application.
3. Install the NSwag library.
4. Import the namespace and create the object.
5. Process the Swagger JSON to C# code.
6. Execute the code and display the result.

Understanding NSwag

A .NET Swagger toolchain called NSwag was created to make it easier to create Swagger specifications, or OpenAPI documents, for APIs constructed using ASP.NET Web API, ASP.NET Core, or other .NET frameworks.

Getting Started with NSwag

NSwag C# Example

Here is an example of code that shows you how to use NSwag to produce C# client code:

using NSwag.CodeGeneration.CSharp;
using NSwag;
using System.Reflection;
using System.CodeDom.Compiler;
using Microsoft.CodeAnalysis;
using System.Net.Http;
using System.IO;
using System.Collections.Generic;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (var wclient = new System.Net.WebClient())
        {
            // Create JSON file data from the Swagger .NET Core web API
            var document = await OpenApiDocument.FromJsonAsync(wclient.DownloadString("http://localhost:5013/swagger/v1/swagger.json"));
            var settings = new CSharpClientGeneratorSettings
            {
                ClassName = "Weather",
                CSharpGeneratorSettings = { Namespace = "Demo" }
            };

            var generator = new CSharpClientGenerator(document, settings);
            var code = generator.GenerateFile();
            var assembly = CompileCode(code);
            var clientType = assembly.GetType("Demo.WeatherClient"); // Replace with your actual client class name
            using (var httpClient = new HttpClient())
            {
                var client = (IApiClient)Activator.CreateInstance(clientType, httpClient);
                var result = await client.GetWeatherForecastAsync();
                foreach (var item in result)
                {
                    Console.WriteLine($"Date: {item.Date} F: {item.TemperatureF} C: {item.TemperatureC} Summary: {item.Summary}");
                }
            }
        }
    }

    static Assembly CompileCode(string code)
    {
        using (var memoryStream = new MemoryStream())
        {
            var assemblyPath = Path.GetDirectoryName(typeof(object).Assembly.Location);
            var references = new List<MetadataReference>
            {
                MetadataReference.CreateFromFile(typeof(object).GetTypeInfo().Assembly.Location),
                MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "Microsoft.AspNetCore.Mvc.dll")),
                MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "System.Private.CoreLib.dll"))
            };

            var compilation = Microsoft.CodeAnalysis.CSharp.CSharpCompilation.Create("ApiClient")
                .WithOptions(new Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary))
                .AddReferences(references)
                .AddSyntaxTrees(Microsoft.CodeAnalysis.CSharp.SyntaxFactory.ParseSyntaxTree(code));

            var emitResult = compilation.Emit(memoryStream);
            if (!emitResult.Success)
            {
                Console.WriteLine("Compilation errors:");
                foreach (var diagnostic in emitResult.Diagnostics)
                {
                    Console.WriteLine(diagnostic);
                }
                return null;
            }
            memoryStream.Seek(0, SeekOrigin.Begin);
            return Assembly.Load(memoryStream.ToArray());
        }
    }

    public interface IApiClient
    {
        // Replace with your actual method name and return type
        Task<List<WeatherForecast>> GetWeatherForecastAsync();
    }

    public class WeatherForecast
    {
        public DateTime Date { get; set; }
        public int TemperatureC { get; set; }
        public int TemperatureF { get; set; }
        public string Summary { get; set; }
    }
}

using NSwag.CodeGeneration.CSharp;
using NSwag;
using System.Reflection;
using System.CodeDom.Compiler;
using Microsoft.CodeAnalysis;
using System.Net.Http;
using System.IO;
using System.Collections.Generic;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (var wclient = new System.Net.WebClient())
        {
            // Create JSON file data from the Swagger .NET Core web API
            var document = await OpenApiDocument.FromJsonAsync(wclient.DownloadString("http://localhost:5013/swagger/v1/swagger.json"));
            var settings = new CSharpClientGeneratorSettings
            {
                ClassName = "Weather",
                CSharpGeneratorSettings = { Namespace = "Demo" }
            };

            var generator = new CSharpClientGenerator(document, settings);
            var code = generator.GenerateFile();
            var assembly = CompileCode(code);
            var clientType = assembly.GetType("Demo.WeatherClient"); // Replace with your actual client class name
            using (var httpClient = new HttpClient())
            {
                var client = (IApiClient)Activator.CreateInstance(clientType, httpClient);
                var result = await client.GetWeatherForecastAsync();
                foreach (var item in result)
                {
                    Console.WriteLine($"Date: {item.Date} F: {item.TemperatureF} C: {item.TemperatureC} Summary: {item.Summary}");
                }
            }
        }
    }

    static Assembly CompileCode(string code)
    {
        using (var memoryStream = new MemoryStream())
        {
            var assemblyPath = Path.GetDirectoryName(typeof(object).Assembly.Location);
            var references = new List<MetadataReference>
            {
                MetadataReference.CreateFromFile(typeof(object).GetTypeInfo().Assembly.Location),
                MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "Microsoft.AspNetCore.Mvc.dll")),
                MetadataReference.CreateFromFile(Path.Combine(assemblyPath, "System.Private.CoreLib.dll"))
            };

            var compilation = Microsoft.CodeAnalysis.CSharp.CSharpCompilation.Create("ApiClient")
                .WithOptions(new Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary))
                .AddReferences(references)
                .AddSyntaxTrees(Microsoft.CodeAnalysis.CSharp.SyntaxFactory.ParseSyntaxTree(code));

            var emitResult = compilation.Emit(memoryStream);
            if (!emitResult.Success)
            {
                Console.WriteLine("Compilation errors:");
                foreach (var diagnostic in emitResult.Diagnostics)
                {
                    Console.WriteLine(diagnostic);
                }
                return null;
            }
            memoryStream.Seek(0, SeekOrigin.Begin);
            return Assembly.Load(memoryStream.ToArray());
        }
    }

    public interface IApiClient
    {
        // Replace with your actual method name and return type
        Task<List<WeatherForecast>> GetWeatherForecastAsync();
    }

    public class WeatherForecast
    {
        public DateTime Date { get; set; }
        public int TemperatureC { get; set; }
        public int TemperatureF { get; set; }
        public string Summary { get; set; }
    }
}

For the API we wish to use, we specify the Swagger specification's URL (swaggerUrl). Then the client code generated and executed into a DLL assembly is defined. OpenApiDocument is employed to load the Swagger document asynchronously from the given URL, using FromJsonAsync. To alter the generated client code, we adjust the code generator's settings (CSharpClientGeneratorSettings). In this example, the produced client code's class name and namespace are specified.

From the loaded Swagger document, we construct an instance of CSharpClientGenerator and use it to produce the client code. The created client code is saved to the designated output path. We respond to any exceptions or errors that may arise during the procedure, displaying the relevant notifications on the console.

NSwag Operation

Integrating NSwag with IronPDF

Developers can improve the workflow for API documentation by utilizing the advantages of both technologies by integrating NSwag with IronPDF. Developers can produce thorough, offline-ready .NET web API documentation that is readily available and shareable by using NSwag to generate Swagger specifications and IronPDF to transform them into PDFs. The following procedures are part of the integration process:

IronPDF excels in HTML to PDF conversion, ensuring precise preservation of original layouts and styles. It's perfect for creating PDFs from web-based content such as reports, invoices, and documentation. With support for HTML files, URLs, and raw HTML strings, IronPDF easily produces high-quality PDF documents.

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

Install IronPDF

• Start the Visual Studio project.
• Choose "Tools" > "NuGet Package Manager" > "Package Manager Console".
• Open your command prompt and in the Package Manager Console, type the following command:

Install-Package IronPdf

• Alternatively, you can install IronPDF by using NuGet Package Manager for Solutions.
• Explore and select the IronPDF package from the search results, and then click the "Install" option. Visual Studio will handle the download and installation on your behalf.

• NuGet will install the IronPDF package and any dependencies required for your project.
• After installation, IronPDF can be utilized for your project.

Implementing Logic

By utilizing NSwag, developers can create API documentation and client code for using APIs more quickly by using CodeGeneration.CSharp in conjunction with IronPDF. The following steps are part of the integration workflow:

1. Generate Client Code: To create C# client code from Swagger specs, use NSwag.CodeGeneration.CSharp. The creation of client classes and methods for communicating with the API endpoints is automated in this step.
2. Utilize NSwag to Get Data: To produce JSON documentation from Swagger specs, use CodeGeneration.CSharp. In this stage, the request/response formats, authentication techniques, and API client endpoints are created into human-readable documentation.
3. Convert JSON to PDF: To convert the generated code result to a PDF document, use IronPDF. In this stage, the HTML text is converted into a polished PDF document that is ready for sharing and distribution.
4. Improve PDF Documentation: Add more content to the PDF documentation using IronPDF, such as headers, footers, watermarks, or unique branding. This stage gives developers the ability to personalize the PDF documentation's look and branding to suit their tastes.

using IronPdf;
using System.Text;
using System.Collections.Generic;

StringBuilder sb = new StringBuilder();

foreach (var item in result)
{
    sb.Append($"<p>Date: {item.Date} F: {item.TemperatureF} C: {item.TemperatureC} Summary: {item.Summary}</p>");
}

var renderer = new HtmlToPdf();
var pdf = renderer.RenderHtmlAsPdf(sb.ToString());
pdf.SaveAs("output.pdf");
Console.WriteLine("PDF generated successfully!");
Console.ReadKey();

using IronPdf;
using System.Text;
using System.Collections.Generic;

StringBuilder sb = new StringBuilder();

foreach (var item in result)
{
    sb.Append($"<p>Date: {item.Date} F: {item.TemperatureF} C: {item.TemperatureC} Summary: {item.Summary}</p>");
}

var renderer = new HtmlToPdf();
var pdf = renderer.RenderHtmlAsPdf(sb.ToString());
pdf.SaveAs("output.pdf");
Console.WriteLine("PDF generated successfully!");
Console.ReadKey();

The code above accesses the retrieved data from the result object and appends the fields Date, TemperatureF, TemperatureC, and Summary to paragraphs in a loop. It then specifies the output file path for the PDF, then notifies the user that a PDF has been generated successfully.

Below is the result from the above code.

Conclusion

CodeGeneration NSwag technologies like CSharp and IronPDF work well together to streamline client code production and API documentation processes. Developers may speed up the creation of API-driven solutions, automate the creation of API documentation, and produce professional-looking PDF publications by integrating these tools into C# applications. NSwag.CodeGeneration.CSharp with IronPDF offers developers a complete solution for efficiently documenting APIs and producing client code in C#, whether they are developing desktop, web, or cloud-based apps.

The Lite bundle includes a perpetual license, one year of software maintenance, and an upgrade to the library. IronPDF offers free licensing with restrictions on redistribution and time. Users can assess the solution during the trial period without having to see a watermark. For additional information on the price and license, please see IronPDF's licensing information. Go to the Iron Software libraries page for additional information about Iron Software's product libraries.