Getting started with the AdoNetDataContext

Published Mon, Nov 9 2009 10:54

Today we’re going to start looking at the AdoNetDataContext. This class expands the DataContext object and uses several specific methods for ensuring the correct interaction with an existing ADO.NET Data Service.

These internal methods added by the AdoNetDataContext are essentially used in identity related operations. In other words, it extends the base DataContext class by introducing several methods which turn on identity support (btw, I’m talking about the stuff we’ve seen in several of the previous posts).

In this post, I’ll be reusing the sample ADO.NET Data Service which is included in MS AJAX preview 6. Here’s the model used internally by the ImageDataService.svc ADO.NET service:

In this case, and since this is just an intro post, we’ll build a simple page which shows all the images returned by this ADO.NET service:

<head runat="server">   
    <style type="text/css">
      .sys-template{
        display: none;
      }      
      img{
        width:320px;
        height:212px;
      }
    </style>
    <script type="text/javascript" 
      src="../Scripts/MicrosoftAjax/start.debug.js">
    </script>
    <script type="text/javascript">
      var _ctx = null;
      Sys.require([Sys.components.adoNetDataContext, 
                   Sys.components.dataView],
      function () {
        _ctx = Sys.create.adoNetDataContext({
            serviceUri: "../Services/ImagesDataService.svc",
            mergeOption: Sys.Data.MergeOption.appendOnly
        });        
    });
    </script>
</head>
<body xmlns:sys="BLOCKED SCRIPTSys"
      xmlns:dv="BLOCKED SCRIPTSys.UI.DataView">
    <div 
      id="myView"
      class="sys-template"
      sys:attach="dv"      
      dv:autofetch="true"
      dv:dataprovider="{{ _ctx }}"
      dv:fetchoperation="Images">
        <h2>{{Name}}</h2>
        <img sys:src="{{Uri}}" sys:alt="{{Name}}" />      
    </div>
</body>

By now, you shouldn’t really be surprised by anything that is shown in the previous snippet. As you can see, the AdoNetDataContext class protects us from all those nasty details associated with the communication with the ImageDataService.svc server side service. I’m not going to show you how to add, edit or remove items because the samples released with preview 6 already have code which shows how to do those things.

On the next post, we’ll see how to do more interesting operations by using the AdoNetQueryBuilder object. Stay tuned for more on MS AJAX.

by luisabreu