Chapter 10 -Function question restated

ChuckASP · April 1st, 2010, 11:50 AM

In Chapter 10 page 345 you enter the following code to call the method/function to return then name entered as a string. But this method has only one argument. How can you specifiy "HelloWorldCallback" as a second argument? I understand what it does, but it doesn't follow the syntax rules. How would I know that the HelloWorld method I wrote could handle another argument and how would I know that this argument is another method and not a paramerter that is used in MY HelloWorld function?
If this can't be answered in this forum, can you direct me to a forum that can?

Thanks,

Chuck

Java script in NameService.vb

Code:

  <WebMethod()> _
  Public Function HelloWorld(ByVal yourName As String) As String
    Return String.Format("Hello {0}", yourName)
  End Function

VB code in WebService.aspx

Code:

NameService.HelloWorld(yourName, HelloWorldCallback);

Imar · April 2nd, 2010, 03:31 PM

Hi Chuck,

The Web Service method is *always* called with one parameter. A strongly typed language such as C# or VB doesn't allow you to pass in less or fewer arguments (unless they are optional which isn't the case in this method).

However, the call to the web service is not a direct call. It's a call to the AJAX framework that in turn calls the web service for you. The code you're using is JavaScript which does allow you to pass more or fewer arguments. To see what you need to pass, look at IntelliSense. Place your cursor after the opening parenthesis after NameService.HelloWorld and press Ctrl+Space. You get a tooltip that tells you you can pass:

1. string yourName
2. onSuccess
3. onFailed
4. userContext

yourName is the parameter defined in the web service method and is required because it's needed in the server side Web Service method. As explained in the book, onSuccess and onFailed are pointers to methods that can be run when the web service succeeds or fails. The userContext is also optional and enables you to pass information from the calling code to the success or failure handlers, in case you need to pass around client state from the original code to the success or failure handlers.

For more info: http://msdn.microsoft.com/en-us/library/bb398995.aspx

Hope this helps,

Imar

Imar · April 2nd, 2010, 03:38 PM

BTW:

Quote:

Last edited by ChuckASP : Yesterday at 05:33 PM. Reason: No answers

I was away for the past couple of days so I couldn't respond earlier.

Cheers,

Imar