Web Service Host Application Implementation

I have been curious for a long time about how Web Service host application is implemented. After I build .NET web service assembly, how can Web Service host application receive request and call the correct method?

From the research I did on Web Service topics these days, I have a concrete idea about how to implement a Web Service host environment. How does ASP.NET platform process Web Service request is beyond my current ability. Here I only talk about the main steps for a normal Web Service host application to process Web Service request.

Reflection is the key for Web Service host application to work.

1. We define a Web Service class and Web Methods by using according attributes. When we deploy the assembly to the host application, the application uses reflection to load the assembly and initialize properties using those attributes:

Assembly assem = Assembly.LoadFrom(assemblyPath);
foreach (Type t in assem.GetExportedTypes())
foreach (MethodInfo info in
t.GetMethods(BindingFlags.Public | BingFlags.Instance)
if (info.IsDefined(typeof(WebMethodAttribute), false))
// Set according properties

Reflection is also used here to generate WSDL file by going through WebMethodAttribute.
2. When a SOAP request comes, the host application parses the SOAP packet to get class name, method name and parameter list.
3. The host application allocates an instance using the class name, either from instance pool or using a singleton
4. The host application finds the method by using method name and calls the method:

MethodInfo info = type.GetMethod(methodName);
object result = info.Invoke(instance, parameters[]);

5. Return the object in SOAP packet if there is no error; otherwise, return exception

The steps above are my simplest design of a Web Service host. I will consider WSE later.