Question

I would like to create a delegate and a method that can be used to call any number of Web services that my application requires:

Example:

public DateCheckResponseGetDate(DateCheckRequest requestParameters) {     delegate object WebMethodToCall(object methodObject);      WebMethodToCall getTheDate = new WebMethodToCall(WebServices.GetTheDate);      return (DateCheckResponse)CallWebMethod(getTheDate , requestParameters); }  public TimeCheckResponse GetTime(TimeCheckRequest requestParameters) {     delegate object WebMethodToCall(object methodObject);      WebMethodToCall getTheTime = new WebMethodToCall(WebServices.GetTheTime);      return (TimeCheckResponse)CallWebMethod(getTheTime, requestParameters); }  private object CallWebMethod(WebMethodToCall method, object methodObject) {     return method(methodObject); } 

But, unfortunately, when I try to compile, I get these errors:

No overload for ‘GetTheDate’ matches delegate ‘WebMethodToCall’ No overload for ‘GetTheTime’ matches delegate ‘WebMethodToCall’

It seems like the delegate should work.

WebServices.GetTheDate and WebServices.GetTheTime both take a single parameter (DateCheckRequest and TimeCheckRequest, respectively) and both return a value.

So doesn’t the delegate match the signature of the two web methods? (both accept and return types derived from object).

Is it possible to use the object type to make a very reusable delegate in .NET 2.0?

Answer 1

I suggest you use a generic delegate such as Func<T, TResult>:

public DateCheckResponseGetDate(DateCheckRequest requestParameters) {     // Split declaration/assignment just to avoid wrapping     Func<DateCheckRequest, DateCheckResponse> method;     method = WebServices.GetTheDate;     return CallWebMethod(method, requestParameters); } 

You’d then make CallWebMethod generic too:

public TResponse CallWebMethod<TRequest, TResponse>     (Func<TRequest, TResponse> method, TRequest request) {     // Whatever you do in here. }