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BOOK: Beginning ASP.NET 4 : in C# and VB
This is the forum to discuss the Wrox book Beginning ASP.NET 4: in C# and VB by Imar Spaanjaars; ISBN: 9780470502211
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Old June 16th, 2011, 12:05 PM
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Default NameService.HelloWorld() success callback method (ch. 10, 356)

I'm wondering why the NameService.HelloWorld() method, which is defined with only one parameter ("yourName") doesn't throw an exception when it is called with two (or possibly three) parameters from the client-side Javascript HelloWorld() function (ch. 10, p. 356).

So the method's return "success callback" calls the second parameter named JS function and if there's an error the third parameter (if there is one) gets called. This is evidently special behavior caused by the preceding of the HelloWorld method with the [WebMethod] attribute. Yes?

I would have expected to see NameService.HelloWorld() as an overloaded method, accepting two or three parameters. Alternately, I would have expected the call to the service to have been done something like

<code>var result = NameService.HelloWorld(yourName);</code>

Then one would process "result", etc.

Please comment or elaborate. Thanks. (Great book, by the way.)
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Old June 16th, 2011, 12:53 PM
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Hi there,

The client code (with 1, 2 or 3 parameters) doesn't call the web service directly. Instead, it calls a proxy class that is created on the fly. This proxy class then has the signature to handle the parameters, the success callbkach and the error callback.

Check out the HTML for the page and look at the <script /> elements. One of them is a reference to a dynamically generated JavaScript class with the JavaScript code required to interact with the Web Service on the server.

Hope this helps,

Imar Spaanjaars
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Author of Beginning ASP.NET 4.5 : in C# and VB, Beginning ASP.NET Web Pages with WebMatrix
and Beginning ASP.NET 4 : in C# and VB.
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