🧼 Building and Consuming SOAP APIs with .NET Core

SOAP (Simple Object Access Protocol) is a protocol for exchanging structured information in web services. While REST APIs are more common today, many enterprise systems still rely on SOAP. .NET Core (now .NET 6/7/8) supports both building and consuming SOAP services.

📦 1. Consuming a SOAP API in .NET Core

.NET Core doesn't include built-in WCF client tooling like .NET Framework, but you can still consume SOAP services using:

✅ Step-by-Step: Consuming a SOAP Web Service

🛠️ Option 1: Use Connected Services

Right-click your project → Add → Connected Service

Choose Microsoft WCF Web Service Reference Provider

Enter the WSDL URL (e.g., http://example.com/service?wsdl)

Click Finish

It auto-generates a service proxy in .cs files.

🛠️ Option 2: Use CLI Tool (dotnet-svcutil)

Install the tool:

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dotnet tool install --global dotnet-svcutil

Generate proxy classes:

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dotnet-svcutil http://example.com/service?wsdl

Add generated files to your project.

Use the client in your code:

csharp

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var client = new MySoapClient(); // generated class

var result = await client.MyMethodAsync("param1");

✅ Ensure you're using a package like System.ServiceModel.Http if needed.

🏗️ 2. Building a SOAP API in .NET Core

While .NET Core does not support full WCF server-side services, you have two main options:

✅ Option 1: Use CoreWCF (Open Source WCF for .NET Core)

CoreWCF is a community-driven port of WCF to .NET Core.

🔧 Setup Example:

Install packages:

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dotnet add package CoreWCF.Http

Create a service contract:

csharp

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[ServiceContract]

public interface ICalculator

{

    [OperationContract]

    int Add(int a, int b);

}

Implement the service:

csharp

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public class CalculatorService : ICalculator

{

    public int Add(int a, int b) => a + b;

}

Configure in Program.cs:

csharp

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var builder = WebApplication.CreateBuilder(args);

builder.Services.AddServiceModelServices();

var app = builder.Build();

app.UseServiceModel(serviceBuilder =>

{

    serviceBuilder.AddService<CalculatorService>();

    serviceBuilder.AddServiceEndpoint<CalculatorService, ICalculator>(

        new BasicHttpBinding(), "/CalculatorService");

});

app.Run();

Access WSDL:

Browse to http://localhost:5000/CalculatorService?wsdl

🔒 Secure your service with transport or message-level security.

✅ Option 2: Host with ASP.NET Core MVC + XML Serialization (Non-SOAP)

If SOAP is not strictly required (i.e., only XML format is needed), use XML-formatted responses in a regular ASP.NET Core API:

csharp

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services.AddControllers().AddXmlSerializerFormatters();

Then decorate your controller and actions to return XML, but this isn’t SOAP compliant.

🧪 3. Testing SOAP Services

Use tools like SoapUI, Postman, or curl (with raw XML payloads).

Validate request structure against the WSDL.

🛡️ 4. Security for SOAP APIs

Use BasicHttpBinding with SSL (HTTPS) for transport-level security.

Consider WS-Security headers if interacting with enterprise services.

Use authentication and authorization middleware in ASP.NET Core.

✅ Summary

Task Approach

Consume SOAP dotnet-svcutil or Connected Services

Build SOAP Use CoreWCF or external frameworks

Secure SOAP Use HTTPS, basic auth, or WS-Security

Test SOAP SoapUI, Postman, curl

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