List View Data Access Modes

• Feb 09, 2023
• 4 minutes to read

Choose Data Access Mode

Client is the default mode in all XAF applications. In ASP.NET Core Blazor Lookup List Views, the default mode is Queryable. The Server, ServerView, DataView, InstantFeedback, and InstantFeedbackView modes optimize how a List View loads and processes data in different scenarios.

• If you have a large number of objects to display in a List View, use Server or InstantFeedback mode.
• If objects you want to display in a List View have a complicated structure (for example, many reference properties), use DataView mode.
• If you have a large number of objects to display in a List View and these objects have a complicated structure, use ServerView or InstantFeedbackView mode.

The following table explains the different modes:

Criteria	Client	Queryable	Server	ServerView	DataView	InstantFeedback	InstantFeedbackView
Supported Platforms	WinForms Web Forms Blazor	Blazor	WinForms Web Forms Blazor	WinForms	WinForms Web Forms	WinForms	WinForms
Supported ORM	EF Core XPO	EF Core XPO	EF Core XPO	XPO	EF Core XPO	EF Core XPO	XPO
Supported ListEditors	all	LookupPropertyEditor	GridListEditor ASPxGridListEditor DxGridListEditor	GridListEditor	GridListEditor SchedulerListEditor PivotGridListEditor ASPxGridListEditor ASPxSchedulerListEditor ASPxPivotGridListEditor	GridListEditor	GridListEditor
Processed object	original object	original object	original object	ObjectRecord	XafDataViewRecord	ObjectRecord	ObjectRecord
Columns available for processing	displayed columns and columns from the Model	displayed columns	displayed columns and columns from the Model	displayed columns and displayable properties from an original collection	displayed columns	displayed columns and displayable properties from an original collection	displayed columns and displayable properties from an original collection
Initially loaded objects	all	displayed	displayed	displayed	all	displayed	displayed
Asynchronous loading	not supported	not supported	not supported	not supported	not supported	supported	supported
Non-persistent properties	supported	supported with limitations	supported with limitations	supported with limitations	supported with limitations	supported with limitations	supported with limitations
In-place editing	supported	not supported	supported (XPO only)	not supported	not supported	not supported	not supported

Once you select the mode, navigate to its topic for more information.

The following video explains the best ways to access and manipulate data in XAF, and how to build high-performance apps.

Non-Persistent Properties Support Limitations

Non-persistent properties are properties that return a value calculated at runtime or store a temporary value in memory. The following list describes their limitations in specific data access modes:

• In ServerView, DataView, and InstantFeedbackView modes, List Editors do not display non-persistent property values.
• In Server, InstantFeedbackView, and Queryable modes, List Editors display non-persistent properties but do not allow you to filter, sort, or group them.

To use non-persistent properties in these modes, decorate them with the PersistentAlias (XPO) or Calculated (EF Core for DataView) attribute. For more information, refer to the following KB article: Is it possible to avoid the “Cannot query a data store using criterion (…)” error and be able to filter, sort and group by non-persistent fields in server mode?.

Specify Data Access Mode

To specify a List View’s data access mode, invoke the Model Editor, navigate to the Views | <ListView> node, and set the IModelListView.DataAccessMode property to one of CollectionSourceDataAccessMode‘s values.

DataAccessMode‘s combo box displays only modes that are compatible with the selected List Editor (a node’s EditorType property). If you use a custom List Editor, specify its supported modes in the static DataAccessModeHelper.RegisterEditorSupportedModes method. Call this method from code executed at design time before the Model Editor is loaded (for example, from a Module’s constructor). Pass the List Editor’s type and a list of supported modes to this method. Otherwise, the Model Editor shows all modes for this List Editor.

C#

using System.Collections.Generic;
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Utils;
// ...
public sealed partial class MySolutionWinModule : ModuleBase {
    public MySolutionWinModule() {
        // ...
        DataAccessModeHelper.RegisterEditorSupportedModes(typeof(CustomListEditor), 
        new List<CollectionSourceDataAccessMode> { CollectionSourceDataAccessMode.Client, CollectionSourceDataAccessMode.Server });
    }
    // ...
}

VB.NET

Imports System.Collections.Generic
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Utils
' ...
Public NotInheritable Partial Class MySolutionWinModule
    Inherits ModuleBase
    Public Sub New()
        ' ...
        DataAccessModeHelper.RegisterEditorSupportedModes(GetType(CustomListEditor), 
        New List(Of CollectionSourceDataAccessMode) _
        From {CollectionSourceDataAccessMode.Client, CollectionSourceDataAccessMode.Server})
    End Sub
    ' ...
End Class

To change data access mode for all List Views in an application (except for autogenerated nested List Views), invoke the Model Editor, navigate to the Options node, and specify its DataAccessMode property. To specify the data access mode for nested List Views, set the IModelListView.DataAccessMode property for each nested List View node as described above.

Note that you can use CollectionSource constructors with the dataAccessMode parameter when you create a List View’s collection source in code.