Using data source controls

• Using an Episerver data source control
• Element attribute versus query parameter
• Creating your own data source controls
• Mapping between control properties and data source parameters

Note: This topic is applicable for sites using Web Forms.

One of the more influential groups of controls included in Episerver CMS are the data source controls. One of the major benefits of using these controls is that they minimize the need of code-behind for day-to-day operations involving reading data and populating various lists, trees, and so on. The new controls supports all or a few of the select, insert, update and delete operations.

Some benefits of using the controls are:

• Minimized need of plumbing code in code-behind.
• Built-in support for select, insert, update and delete.
• A contract that fits many of the built-in .NET controls and third-party controls.

You can categorize the data source controls as Hierarchical, Tabular, or both depending on how they can deliver data.

• Hierarchical data source controls expose data in a hierarchical fashion (parent – child), which you can use for tree views such as the TreeView and Menu controls in ASP.NET.
• Most controls serve data in tabular fashion, which you can use to list controls such as the Repeater, DataList, GridView, and so on.

Note: An important difference between hierarchical and tabular data sources are that hierarchical data sources are read-only whereas the tabular data sources can support inserting, updating, and deleting.

The following controls implement the IHierarchicalDataSource interface and can generate data for tree view controls or menus:

• PageDataSource
• CategoryDataSource
• FileSystemDataSource

To create your own tabular data source controls, use the base class GenericDataSource.

Using an Episerver data source control

The data source classes are intended to be used in markup rather than coded against or inherited from, so you should have little need to add your own code-behind. If you do need additional functionality, you should inherit from the GenericDataSource control and create classes that suit your needs.

The data source controls work as any standard control in an .aspx page. See the templates and demo site packages available from EPiServer World for examples and information about implementing the controls shipped with Episerver CMS.

Element attribute versus query parameter

When you populate a data source you usually use a QueryStringParameter to read a selection of objects from the database.  You can define a value for a member of the object as an attribute in the asp element and as a parameter in the query string. In this case, the query string definition takes precedence over the asp attribute. Consider the following example:

<EPiServer:CategoryDataSource
    runat="server"
    ID="CategoryData"
    IncludeRootCategory="true">
    <SelectParameters>
        <asp:QueryStringParameter
            Name="ID"
            QueryStringField="ID"
            Type="Int32" />
        <asp:QueryStringParameter
            Name="IncludeRootCategory"
            QueryStringField="IncludeRootCategory"
            Type="Boolean"
            DefaultValue="false" />
    </SelectParameters>
</EPiServer:CategoryDataSource>

Because IncludeRootCategory is defined twice (being set to true in the tag definition and false in the QueryStringParameter), the value set in the query string parameter will be used. If no query string parameter named IncludeRootCategory is specified, it is default value will be used, in this case false. For information about using parameters with Data Source Controls, see Microsoft’s article Using Parameters with Data Source Controls.

Creating your own data source controls

Designing your own data source controls is a matter of inheriting from the GenericDataSource class. The following lines of code show how the TabDefinitionDataSource is defined. There is very little code involved to get access to the basic functionality.

public class TabDefinitionDataSource :
GenericDataSource<TabDefinition, TabDefinitionCollection, int>
{
    protected override TabDefinition CreateItem(List<TabDefinition> items)
    {
        return new TabDefinition();
    }

    protected override List<TabDefinition> ListItems()
    {
        return ToList(TabDefinition.List());
    }

    protected override TabDefinition LoadItem(int key)
    {
        return TabDefinition.Load(key);
    }

    protected override void SaveItem(TabDefinition item)
    {
        item.Save();
    }

    protected override void DeleteItem(TabDefinition item)
    {
        item.Delete();
    }
}

GenericDataSource<TObject, TCollection, TKey> has the following type parameters:

Business Objects
Before you can create your data source control type, you need to have a class, your business object, that handles the data that you want to present. In the sample above the class used for this is TabDefinition. This class is responsible for reading and saving data from the database.

If you do not need to implement a specialized behavior in your collection of business objects, you can use the generic List provided by the .NET Framework as described in the following short sample:

...
...
public class MyObjectDataSource :
GenericDataSource<MyObject, List<MyObject>, int>
{

...
...

Mapping between control properties and data source parameters

A common way to limit a result set of a data source control is to provide it parameters in the SelectParameters collection (see Parameter). This is supported by most of the Episerver data source controls by allowing certain control properties to be overridden by a parameter value. You can specify the following properties using Parameters for a given Episerver data source control. The parameter name must correspond to the property name.

• PageDataSource

  Property	Type
  AccessLevel	EPiServer.Security.AccessLevel
  PageLink	EPiServer.Core.PageReference
  PageLinkProperty	String
  IncludeRootPage	Bool

• SearchDataSource

  Property	Type
  AccessLevel	EPiServer.Security.AccessLevel
  PageLink	EPiServer.Core.PageReference
  PageLinkProperty	String
  IncludeRootPage	Bool
  OnlyWholeWords	Bool
  SearchQuery	String
  SearchFiles	Bool
  SearchLocations	String
  MainCatalog	String
  MainScope	String
  MaxAllowHits	Integer

• CategoryDataSource

  Property	Type
  IncludeRootCategory	Bool

• FileSystemDataSource

  Property	Type

• LanguageDataSource

  Property	Type

• PageDefinitionDataSource

  Property	Type
  Dynamic	Bool
  PageTypeID	Integer

• PageDefinitionTypeDataSource

  Property	Type
  ID	Integer

• PageVersionDataSource

  Property	Type
  PageLink	EPiServer.Core.PageReference
  LanguageBranch	String

• TabDefinitionDataSource

  Property	Type
  ID	Integer

• MembershipUserDataSource

  Property	Type
  UserName	string

• SoftLinkDataSource

  Property	Type
  PageLink	EPiServer.Core.PageReference
  ListReferencing	Bool

Related topics

• System.Web.UI.WebControls.Parameter
• QueryStringParameter
• Using Parameters with Data Source Controls