EntityInstantFeedbackSource Class

The data source for the GridControl and SearchLookUpEdit that binds these controls to Entity Framework 4+ model classes in Instant Feedback Mode.

Namespace: DevExpress.Data.Linq

Assembly: DevExpress.Data.v18.2.dll

Declaration

C#

[ToolboxBitmap(typeof(ResFinder), "Bitmaps256.EntityInstantFeedbackSource.bmp")]
[ToolboxTabName("DX.18.2: Data & Analytics")]
public class EntityInstantFeedbackSource :
    Component,
    IListSource,
    IDXCloneable

VB.NET

<ToolboxBitmap(GetType(ResFinder), "Bitmaps256.EntityInstantFeedbackSource.bmp")>
<ToolboxTabName("DX.18.2: Data & Analytics")>
Public Class EntityInstantFeedbackSource
    Inherits Component
    Implements IListSource,
               IDXCloneable

Remarks

Instant Feedback binding mode is an improvement over regular server mode. In server mode, the Grid Control loads data in small portions and delegates all data operations (sorting, grouping, filtering and calculating summaries) to the data server. This is the key to the server mode’s high efficiency when working with large volumes of data. The only drawback to using server mode involves data operations when the connection to the server is slow. In this instance, the bound control freezes until the data server completes operations and retrieves results. With Instant Feedback binding mode, data operations are performed asynchronously in a background thread, and both the bound control and the application remain highly responsive. Currently, this mode is supported by the GridControl and SearchLookUpEdit controls.

For additional information on Instant Feedback mode, refer to the Large Data Sources: Server and Instant Feedback Modes section.

Note

The EntityInstantFeedbackSource is a read-only data source.

C#

public partial class Form1 : Form {
    private void Form1_Load(object sender, EventArgs e) {
        efInstantFeedbackSource1.KeyExpression = "EmployeeID";
        efInstantFeedbackSource1.GetQueryable += efInstantFeedbackSource1_GetQueryable;
        efInstantFeedbackSource1.DismissQueryable += efInstantFeedbackSource1_DismissQueryable;
        gridControl1.DataSource = efInstantFeedbackSource1;
    }
    void efInstantFeedbackSource1_GetQueryable(object sender, GetQueryableEventArgs e) {
        NorthwindEntities objectContext = new NorthwindEntities();
        e.QueryableSource = objectContext.Employees;
        e.Tag = objectContext;            
    }
    void efInstantFeedbackSource1_DismissQueryable(object sender, GetQueryableEventArgs e) {
        ((NorthwindEntities)e.Tag).Dispose();         
    }
}

VB.NET

Partial Public Class Form1
    Inherits Form
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs)
        efInstantFeedbackSource1.KeyExpression = "EmployeeID"
        AddHandler efInstantFeedbackSource1.GetQueryable, AddressOf efInstantFeedbackSource1_GetQueryable
        AddHandler efInstantFeedbackSource1.DismissQueryable, AddressOf efInstantFeedbackSource1_DismissQueryable
        gridControl1.DataSource = efInstantFeedbackSource1
    End Sub
    Private Sub efInstantFeedbackSource1_GetQueryable(ByVal sender As Object, ByVal e As GetQueryableEventArgs)
        Dim objectContext As New NorthwindEntities()
        e.QueryableSource = objectContext.Employees
        e.Tag = objectContext
    End Sub
    Private Sub efInstantFeedbackSource1_DismissQueryable(ByVal sender As Object, ByVal e As GetQueryableEventArgs)
        CType(e.Tag, NorthwindEntities).Dispose()
    End Sub
End Class

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the EntityInstantFeedbackSource class.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

mvvmexpenses-sample-application-t254492/CS/MVVMExpenses/Common/DataModel/EntityFramework/InstantFeedbackSource.cs#L20

where TEntity : class {
readonly EntityInstantFeedbackSource source;
readonly PropertyDescriptorCollection threadSafeProperties;

VB.NET

mvvmexpenses-sample-application-t254492/VB/MVVMExpenses/Common/DataModel/EntityFramework/InstantFeedbackSource.vb#L18

Implements IInstantFeedbackSource(Of TEntity)
Private ReadOnly _source As EntityInstantFeedbackSource
Private ReadOnly _threadSafeProperties As PropertyDescriptorCollection

Inheritance

Object

MarshalByRefObject

Component

EntityInstantFeedbackSource