Accessing a .NET Webservice via JavaScript

Discussion in 'ASP .Net Web Services' started by AlBruAn, Aug 14, 2007.

  1. AlBruAn

    AlBruAn Guest

    I have a need for a Web Service to retrieve values from a SQL Server database
    to populate a dropdown list. That, without any further explanation, sounds
    quite simple. The problem is the dropdown list is in FCKeditor, an
    open-source WYSIWYG HTML editor written entirely in JavaScript. When the
    editor is displayed, I need to query the database based on values selected
    from two standard ASP dropdown lists on the page and return the results of
    that query to populate the dropdown list in FCKeditor.

    Should I write a section of JavaScript in my page to retrieve the selected
    indexes of the two ASP dropdown lists once a selection is made and have the
    JavaScript function call the Web Service? If so, how do I write the Web
    Service to accept the two pieces of information? And how, for that matter,
    do I send the message to the Web Service from JavaScript? This thing has me
    really confused.
     
    AlBruAn, Aug 14, 2007
    #1
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  2. Hi,

    AlBruAn wrote:
    > I have a need for a Web Service to retrieve values from a SQL Server database
    > to populate a dropdown list. That, without any further explanation, sounds
    > quite simple. The problem is the dropdown list is in FCKeditor, an
    > open-source WYSIWYG HTML editor written entirely in JavaScript. When the
    > editor is displayed, I need to query the database based on values selected
    > from two standard ASP dropdown lists on the page and return the results of
    > that query to populate the dropdown list in FCKeditor.
    >
    > Should I write a section of JavaScript in my page to retrieve the selected
    > indexes of the two ASP dropdown lists once a selection is made and have the
    > JavaScript function call the Web Service?


    Yes.

    > If so, how do I write the Web
    > Service to accept the two pieces of information?


    First, you got to decide if you really want to use a Web Service
    (meaning, SOAP) for this quite simple method. Probably it's not the best
    idea. SOAP is very bloated, and parsing a SOAP message using pure
    JavaScript is quite complex.

    The best idea is probably to rather use an ASHX custom handler on the
    server, and have it send back some XML data to the calling client. This
    is rather simple, see here:
    http://www.galasoft.ch/mydotnet/articles/article-2006100601.aspx


    > And how, for that matter,
    > do I send the message to the Web Service from JavaScript? This thing has me
    > really confused.


    Unfortunately I never managed to write the article's part two, which is
    how to use JavaScript to call the ASHX page you created above.
    Thankfully, it's not very complicated. You do this using the
    XmlHttpRequest object, which is available in IE, Firefox and other browsers.

    To send a request using XmlHttpRequest, you should check the various
    tutorials available online.
    I recommend:
    http://www.ajaxtoolbox.com/

    HTH,
    Laurent
    --
    Laurent Bugnion [MVP ASP.NET]
    Software engineering, Blog: http://www.galasoft.ch
    PhotoAlbum: http://www.galasoft.ch/pictures
    Support children in Calcutta: http://www.calcutta-espoir.ch
     
    Laurent Bugnion, MVP, Aug 17, 2007
    #2
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