Ajax command parsing

[Ranthalion]

Hi,

I am creating a web app with VB.NET 1.1 using AJAX. I was wondering if there is a better way to handle events than what I am doing, without downloading an ajax framework.

My method:
Each button on web form calls javascript that creates an xml fragment and posts it to a class that handles ajax requests for the page.
XML:

<AjaxRequest>
<Command>Foo</Command>
<Params>
<Param name="param1">Bar</Param>
<Param name="param2">Again</Param>
</Params>
</AjaxRequest>


The code on the server pulls out the command field and runs it through a select case to determine which function to call.


Imports System.Web
Imports System.Xml

Public Class Ajax
Implements IHttpHandler

Public ReadOnly Property IsReusable() As Boolean Implements System.Web.IHttpHandler.IsReusable
Get
Return True
End Get
End Property

'Here is where the action is...
Public Sub ProcessRequest(ByVal context As System.Web.HttpContext) Implements System.Web.IHttpHandler.ProcessRequest
Dim xmlDoc As XmlDocument

'If the XML document was submitted via post method, then load it in the DOM document
If (context.Request.InputStream.Length > 0 And context.Request.ContentType.ToString().IndexOf("/xml") > 0) Then
xmlDoc = New XmlDocument
xmlDoc.Load(context.Request.InputStream)

Select Case xmlDoc.GetElementsByTagName("Command").Item(0).InnerText
Case "Bar"
Call Bar()
Case "Func2"
Call Func2()
Case "HelloWorld"
Call HelloWorld()
...etc...
End Select

End If
End Sub

Public Sub Bar()
'Get params, do some work, and return something in the Response...
End Sub
End Class


Instead of this select case, are there better methods? It just seems like there should be...

Thanks,

Ranthalion

[wildfrog]

Instead of this select case, are there better methods? It just seems like there should be...You could use some kind of map (key/value collection) between a specific string (the command) and a delegate (the function to call). Then instead of the select-case stament you simply grab the command from the xml, then lookup the correspoing delegate in the map, and then call the delegate.

And AFAIK it would be cleaner to use XPath to lookup the command instead of GetElementsByTagName.

- petter

[Ranthalion]

Thanks. The map seems like it would be pretty much the same thing as the Select Case implementation. Whenever I add a new function, I would have to manually update the map to contain the new command string and function name. I'll think about it some more, though.

I'm not familiar with XPath yet, so I'll definately check that out. This is the first project that uses xml. Thanks again!