C# How to: Generate a Web Service from WSDL

Article purpose

Web Service Definition Language (WSDL) is an Xml based schema that exactly details the custom data types and web service methods exposed by a web service. Developers usually generate web service client proxy code in order to call into web services. Since WSDL is an exact description of a web service it is also possible to generate code that represents the service in the form of web method stubs. This article illustrates how to generate a web service from WSDL.

Introduction

I’ve often found myself in a scenario where I have to interface with third parties via web services. It is often the case that third party service are proprietary, usually I find that I have very little control over the web services I’m required to interface to. Countless hours are wasted because of out dated test environments, missing/incorrect security certificates or even just trying to get hold of log files.

Time spent on development and testing can be significantly reduced in most cases if I had a local copy of a web service available to me. Having access to source code would be even more beneficial, being able to manipulate the data returned, testing timeouts etc. After surprisingly little effort I manage to develop a utility application capable of generating web method stubs and custom defined types in C# source code. The only required input in generating a web service is the WSDL of an existing web service.

Sample source code

This article is accompanied by sample source code in a Visual Studio project which is available for download here.

Input Web service WSDL

The sample source accompanying this article defines a very simplistic web service, consisting of one web method HelloWorld(). The source code is listed below:

 [WebService (Namespace = "http://softwarebydefault.com" )]

 [WebServiceBinding (ConformsTo = WsiProfiles.BasicProfile1_1)]

 [System.ComponentModel.ToolboxItem (false )]

 public class TestWebService : System.Web.Services.WebService

     [WebMethod ]

     public string  HelloWorld()

         return "Hello World";

The resulting WSDL is generated as illustrated by the following snippet:

<?xml version="1.0" encoding="utf-8"?>
<wsdl:definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/" xmlns:tns="http://softwarebydefault.com" xmlns:s="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://schemas.xmlsoap.org/wsdl/soap12/" xmlns:http="http://schemas.xmlsoap.org/wsdl/http/" targetNamespace="http://softwarebydefault.com" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">
  <wsdl:types>
    <s:schema elementFormDefault="qualified" targetNamespace="http://softwarebydefault.com">
      <s:element name="HelloWorld">
        <s:complexType />
      </s:element>
      <s:element name="HelloWorldResponse">
        <s:complexType>
          <s:sequence>
            <s:element minOccurs="0" maxOccurs="1" name="HelloWorldResult" type="s:string" />
          </s:sequence>
        </s:complexType>
      </s:element>
    </s:schema>
  </wsdl:types>
  <wsdl:message name="HelloWorldSoapIn">
    <wsdl:part name="parameters" element="tns:HelloWorld" />
  </wsdl:message>
  <wsdl:message name="HelloWorldSoapOut">
    <wsdl:part name="parameters" element="tns:HelloWorldResponse" />
  </wsdl:message>
  <wsdl:portType name="TestWebServiceSoap">
    <wsdl:operation name="HelloWorld">
      <wsdl:input message="tns:HelloWorldSoapIn" />
      <wsdl:output message="tns:HelloWorldSoapOut" />
    </wsdl:operation>
  </wsdl:portType>
  <wsdl:binding name="TestWebServiceSoap" type="tns:TestWebServiceSoap">
    <soap:binding transport="http://schemas.xmlsoap.org/soap/http" />
    <wsdl:operation name="HelloWorld">
      <soap:operation soapAction="https://softwarebydefault.com/HelloWorld" style="document" />
      <wsdl:input>
        <soap:body use="literal" />
      </wsdl:input>
      <wsdl:output>
        <soap:body use="literal" />
      </wsdl:output>
    </wsdl:operation>
  </wsdl:binding>
  <wsdl:binding name="TestWebServiceSoap12" type="tns:TestWebServiceSoap">
    <soap12:binding transport="http://schemas.xmlsoap.org/soap/http" />
    <wsdl:operation name="HelloWorld">
      <soap12:operation soapAction="https://softwarebydefault.com/HelloWorld" style="document" />
      <wsdl:input>
        <soap12:body use="literal" />
      </wsdl:input>
      <wsdl:output>
        <soap12:body use="literal" />
      </wsdl:output>
    </wsdl:operation>
  </wsdl:binding>
  <wsdl:service name="TestWebService">
    <wsdl:port name="TestWebServiceSoap" binding="tns:TestWebServiceSoap">
      <soap:address location="http://localhost:6078/TestWS.asmx" />
    </wsdl:port>
    <wsdl:port name="TestWebServiceSoap12" binding="tns:TestWebServiceSoap12">
      <soap12:address location="http://localhost:6078/TestWS.asmx" />
    </wsdl:port>
  </wsdl:service>
</wsdl:definitions>

Generating the Web service from input WSDL

The crux of this article revolves around the Generate method defined in the associated sample source code. The method makes use of the ServiceDescription and ServiceDescriptionImporter classes to reference the WSDL generated earlier. The code defined by the Generate method is very similar to the code that would generate web service client proxy code. Make note of the Style property of the ServiceDescriptionImporter object being set to ServiceDescriptionImportStyle.Server. By setting the style to server we indicate that any code generated should reflect the server interface. Had the property being set to ServiceDescriptionImportStyle.Client web service client proxy code would be generated.

After importing the service descriptions as defined by the specified WSDL and if no errors occurred we generate C# source code based on the service descriptions imported. The resulting source code generated is then saved to the file system based on the file path passed as method parameter.

 public  static  void  Generate(string  wsdlPath, string  outputFilePath)

     if  (File.Exists(wsdlPath) == false )

         return;

     ServiceDescription  wsdlDescription = ServiceDescription .Read(wsdlPath);

     ServiceDescriptionImporter  wsdlImporter = new  ServiceDescriptionImporter ();

     wsdlImporter.ProtocolName = "Soap12";

     wsdlImporter.AddServiceDescription(wsdlDescription, null , null );

     wsdlImporter.Style = ServiceDescriptionImportStyle .Server;

     wsdlImporter.CodeGenerationOptions = System.Xml.Serialization.CodeGenerationOptions .GenerateProperties;

     CodeNamespace codeNamespace = new  CodeNamespace();

     CodeCompileUnit codeUnit = new  CodeCompileUnit();

     codeUnit.Namespaces.Add(codeNamespace);

     ServiceDescriptionImportWarnings importWarning = wsdlImporter.Import(codeNamespace, codeUnit);

     if  (importWarning == 0)

         StringBuilder stringBuilder = new StringBuilder();

         StringWriter stringWriter = new StringWriter(stringBuilder);

         CodeDomProvider codeProvider = CodeDomProvider.CreateProvider("CSharp");

         codeProvider.GenerateCodeFromCompileUnit(codeUnit, stringWriter, new CodeGeneratorOptions());

         stringWriter.Close();

         File.WriteAllText(outputFilePath, stringBuilder.ToString(), Encoding.UTF8);

     else

         Console.WriteLine(importWarning);

Notice the use of the CodeDomProvider class, creating an instance of this class allows us to generate source code. This class can also be used to compile source code to assemblies, in essence it allows developers access to a set of compilers accessible from code. As described by MSDN documentation:

A CodeDomProvider implementation typically provides code generation and/or code compilation interfaces for generating code and managing compilation for a single programming language. Several languages are supported by CodeDomProvider implementations that ship with the Windows Software Development Kit (SDK). These languages include C#, Visual Basic, C++, and JScript. Developers or compiler vendors can implement the ICodeGenerator and ICodeCompiler interfaces and provide a CodeDomProvider that extends CodeDOM support to other programming languages.

The Generated Code

The code generated comes in the form of abstract classes and methods. The snippet below illustrates the raw generated code:

 [System.CodeDom.Compiler.GeneratedCodeAttribute("WSDLToWebService" , "1.0.0.0" )]

 [System.Web.Services.WebServiceAttribute(Namespace="http://softwarebydefault.com" )]

 [System.Web.Services.WebServiceBindingAttribute(Name="TestWebServiceSoap12" , Namespace="http://softwarebydefault.com" )]

 public  abstract  partial  class  TestWebService  : System.Web.Services.WebService {

     [System.Web.Services.WebMethodAttribute()]

     [System.Web.Services.Protocols.SoapDocumentMethodAttribute("https://softwarebydefault.com/HelloWorld" ,

         RequestNamespace="http://softwarebydefault.com" , ResponseNamespace="http://softwarebydefault.com" ,

         Use=System.Web.Services.Description.SoapBindingUse.Literal,

         ParameterStyle=System.Web.Services.Protocols.SoapParameterStyle.Wrapped)]

     public  abstract  string  HelloWorld();

The code generated compiles without issue, but being declared abstract prevents the code from functioning as a web service implementation. I find the easiest method is to refactor the code instead of implementing inheritance. The snippet listed below represents the generated code refactored to reflect a web service implementation.

[System.CodeDom.Compiler.GeneratedCodeAttribute ("WSDLToWebService" , "1.0.0.0" )]

[System.Web.Services.WebServiceAttribute (Namespace = "http://softwarebydefault.com" )]

[System.Web.Services.WebServiceBindingAttribute (Name = "TestWebService" , Namespace = "http://softwarebydefault.com" )]

public  class  TestWebService  : System.Web.Services.WebService

     [System.Web.Services.WebMethodAttribute()]

     [System.Web.Services.Protocols.SoapDocumentMethodAttribute("https://softwarebydefault.com/HelloWorld" ,

     RequestNamespace = "http://softwarebydefault.com" , ResponseNamespace = "http://softwarebydefault.com" ,

     Use = System.Web.Services.Description.SoapBindingUse.Literal,

     ParameterStyle = System.Web.Services.Protocols.SoapParameterStyle.Wrapped)]

     public  string  HelloWorld()

         return  "Hello Generated World" ;

The TestWebService class and HelloWorld method is now no longer defined as abstract. In addition HelloWorld now defines a method body as required by not being an abstract method anymore.

About the Icons

I’ve written a number of articles exploring the topic of Image Colour filters. All of the Light bulb icon images featured in this article were generated from same source image, each having been manipulated by various colour filters. I made use of sample applications accompanying some of the articles I’ve published.

If you are interested in Image filters or would like to download the sample applications and source code please have a look at the following links to articles published on this site:

Examples of Image Filters

The original source image used to generate the icon images featured in this article has been licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license and can be downloaded from Wikipedia.

Software by Default