A Beginner's Guide to the DataSource Control

The DataSource control (new in ASP.net) is a real timesaver for programmers. Now, instead of writing all the code to populate a grid, it’s possible to use a DataSource control, a new ‘genre’ (if you will) of controls, which provide ‘declarative’ access to data. Though I won’t go into all of them (there are several – SQL, Access, XML, SiteMapDataSource and ObjectDataSource controls), I will cover the Database type DataControl (SQLDataSource and AccessDataSource). The properties are similar for both.

In general, at the basic level, what happens is that each DataSource control has many properties which the programmer populates, like the ConnectionString property and the SQL statement properties (SelectCommand, UpdateCommand, etc).

Once these properties have been provided, a presentation control (like a GridView, FormView or DetailsView control, all new in v2.0 of the Dotnet Framework) can point to the DataSource control, and without any coding at all – voila – a web page has been created that displays data from a data source. Naturally, it doesn’t do much except presentation, at this point, but like was said earlier, this is just the basic leve..

For the SelectCommand, one can choose a pure SQL Select statement (Select [field name list] from [Table name]), or a Stored Procedure. If a Stored Procedure is used, the ‘SelectCommandType’ property needs to be set thusly:

SelectCommandType="StoredProcedure"

Here, we might add that a new section has been added to the Web.Config file, specifically for Connection Strings. And, as you might figure, the section is called ‘ConnectionStrings’, and is placed inside the Configuration section of the Web.Config file, much like the AppSettings section was used earlier, for the connection strings. The main difference here, is, instead of ‘add key’, we use ‘add name’:

<connectionStrings>
<add name="Pubs" connectionString="Server=YourServerIP;uid=YourUID;pwd=YourPWD;database=YourDB"
    providerName="System.Data.SqlClient" />
</connectionStrings>

As you can also see (above), the providerName attribute is added. With this, the page never needs to bother Importing the Namespaces, which are specific to the particular data connection. Of course, for Access, you’d use OleDb, here, instead of SQLclient.

To address that ConnectionString, in your DataSource control, (notice the new tag definition) merely do something like this:

ConnectionString="<%$ ConnectionStrings:Pubs %>"

Of course, if you would rather do it manually, you can just code the connection string manually here, also.

Now – you are probably saying to yourself, “That’s easy enough, but what about Where clauses?”. That’s fairly easy also, at least easier than it was in the past. The DataSource controls have other attributes, especially for this. For the SelectCommand, there is a SelectParameters attribute (for UpdateCommand, UpateParameters, for the DeleteCommand, DeleteParameters, etc). Here’s an example:

<asp:SqlDataSource ID="SqlDataSource1" runat="server"
  ConnectionString="<%$ ConnectionStrings:Pubs %>"
  SelectCommand="SELECT [au_id], [au_lname], [au_fname], [state] FROM [authors] WHERE [state] = @state">
  <SelectParameters>
    <asp:ControlParameter Name="state" ControlID="ddlStates" PropertyName="SelectedValue" />
  </SelectParameters>
</asp:SqlDataSource>

Here, we set a SelectParameter, with the ControlID, point it to the control which the Where Clause will get it’s defining data, and assign the ‘SelectedValue’ (or ‘SelectedItem.Text’), to the Property name attribute of the SelectParamenter. That’s really all there is to it!

At this point, all that’s left to do is to assign this DataSource ID to the DataSource property of the presentation control of your choice, like so:

<asp:GridView id="MyGridView" RunAt="Server" DataSourceID="SQLDataSource1"/>

Also – one property of the DataSource Control is DataSourceMode. Here, you can assign ‘DataReader’ or ‘DataSet’, though, from what I can tell, the default is ‘DataSet’, so you really don’t need to assign the property at all, if that’s what you want. And, if you want paging and sorting, that IS what you will want.

Technically, no coding was placed on the page, even though, with just 2 controls, a DataSource Control, and a GridView, it’s easy to display the received data from your database!

As an additional note here, there are a number of other Parameter Classes which are able to be used here, like SessionParameters, QueryStringParameters, CookieParameters and FormParameters. Here, we only looked at the SelectParameters attribute, based on using the Selectcommand, due to the sample shown. However, there are also the following Commands, used in the DataSource Controls:
InsertCommand, UpdateCommand and Deletecommand
Each of those can use the different Parameter Classes mentioned here, depending on the use and needs for the individual DataSource needs.

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