Function Overloading in Web Services

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Introduction

The function overloading in Web Service is not as straightforward as in class. While trying to overload member function, we make two or more methods with the same name with different parameters. But this will not work in web services and will show runtime error because WSDL is not supported by the same method name.

Overloading Web Services

While trying to overload Web Methods in Web Services and after doing the build, it will work successfully. But when we try to run or consume, it will show an error message. We can show this using an example.

namespace TestOverloadingWebService
{ 
    [WebService(Namespace = "http://tempuri.org/", Description=" <b> Function 
    overloading in Web Services </b>")] 
public class OverloadingInWebService : System.Web.Services.WebService 
{ 
    [WebMethod()] 
    public int Add(int a, int b) 
    { 
        return (a + b); 
    } 
    [WebMethod()] 
    public float Add(float a, float b) 
    { 
        return (a + b); 
    } 
} 
}

In the above example, we made one web service having class OverloadingInWebService. In the Web Service, we have added attribute Description, which is used to describe the web service purpose to client. In the above Web Service, we have two overloaded WebMethods:

public int Add(int a, int b) 

and

public float Add(float a, float b)

While running this Web service, it will show the following runtime error.

Solution for the Above Error

The procedure to solve this problem is very easy. Start each method with a Web Method attribute. Add Description property to add a description of web method and MessageName property to change web method name.

[WebMethod(MessageName = "<name>", Description = "<description>")]

namespace TestOverloadingWebService 
{ 
    [WebService(Namespace = "http://tempuri.org/", Description=" <b> Function 
    overloading in Web Services </b>")] 
public class OverloadingInWebService : System.Web.Services.WebService 
{ 
    [WebMethod(MessageName = "AddInt", Description = "Add two integer 
        Value", EnableSession = true)] 
    public int Add(int a, int b) 
    { 
        return (a + b); 
    } 
    [WebMethod(MessageName = "AddFloat", Description = "Add two Float  
        Value", EnableSession = true)] 
    public float Add(float a, float b) 
    { 
        return (a + b); 
    } 
} 
}

Reason for the Above Error

The Overloading is supported by web services. But when WSDL (Web Service Description Language) is generated, it will not be able to make the difference between methods because WSDL does not deal on the base of parameters. By passing web methods –‘MessageName Property’, it changes the method name in WSDL. See the WSDL given below, the operation name is Add but the input method name is AddInt as well as output method name is also same (AddInt). The same will apply for Float also.

<wsdl:operation name="Add"> 
            <wsdl:documentation xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">Add 
            two integer Value</wsdl:documentation> 
            <wsdl:input name="AddInt" message="tns:AddIntSoapIn" /> 
            <wsdl:output name="AddInt" message="tns:AddIntSoapOut" /> 
</wsdl:operation> 
<wsdl:operation name="Add"> 
            <wsdl:documentation xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">Add     
            two Float Value</wsdl:documentation> 
            <wsdl:input name="AddFloat" message="tns:AddFloatSoapIn" /> 
            <wsdl:output name="AddFloat" message="tns:AddFloatSoapOut" /> 
</wsdl:operation>

History

• 9^th October, 2008: Initial post