ASPxPivotGrid.CustomLoadCallbackState Event

Allows you to load the ASPxPivotGrid’s callback state, which was previously saved by handling the ASPxPivotGrid.CustomSaveCallbackState event.

Namespace: DevExpress.Web.ASPxPivotGrid

Assembly: DevExpress.Web.ASPxPivotGrid.v24.1.dll

NuGet Package: DevExpress.Web

Declaration

C#

public event PivotGridCallbackStateEventHandler CustomLoadCallbackState

VB.NET

Public Event CustomLoadCallbackState As PivotGridCallbackStateEventHandler

Event Data

The CustomLoadCallbackState event's data class is PivotGridCallbackStateEventArgs. The following properties provide information specific to this event:

Property	Description
CallbackState	Gets or sets the ASPxPivotGrid’s callback state.
Handled	Gets or sets whether a callback state saving/loading operation is handled manually, so no default processing is required.

Remarks

By default, the ASPxPivotGrid stores its intermediate state (callback state) in a specific hidden CallbackState field within a web page. In some cases, especially when the ASPxPivotGrid is connected to a huge OLAP cube, this state can be rather large, thereby affecting your web application performance. To reduce the web page size, you can store the ASPxPivotGrid’s callback state in a custom manner, for instance, in the Session object or a static variable. For this purpose, you should handle the ASPxPivotGrid.CustomSaveCallbackState and CustomLoadCallbackState events.

Handling the CustomLoadCallbackState event, you can manually load the previously saved callback state (by assigning it to the PivotGridCallbackStateEventArgs.CallbackState property). Set the PivotGridCallbackStateEventArgs.Handled property to true within the event’s handler to use a custom saving / loading mechanism instead of the default.

Note

Note that if you do not handle the ASPxPivotGrid.CustomSaveCallbackState and CustomLoadCallbackState events, the ASPxPivotGrid’s callback state depends on the System.Web.UIControl.UniqueID property value.

Example

This example demonstrates how the ASPxPivotGrid.CustomSaveCallbackState and ASPxPivotGrid.CustomLoadCallbackState events can be handled to preserve the ASPxPivotGrid’s callback state within a Session.

Default.aspx

<dxwpg:ASPxPivotGrid ID="ASPxPivotGrid1" runat="server" 
OLAPConnectionString="provider=MSOLAP;
                        data source=https://demos.devexpress.com/Services/OLAP/msmdpump.dll; 
                        initial catalog=Adventure Works DW Standard Edition;
                        cube name=Adventure Works;" 
OnCustomLoadCallbackState="ASPxPivotGrid1_CustomLoadCallbackState" 
OnCustomSaveCallbackState="ASPxPivotGrid1_CustomSaveCallbackState">
    <Fields>
        <dxwpg:PivotGridField ID="fieldCountry1" Area="RowArea" AreaIndex="0" 
            Caption="Country"
            FieldName="[Customer].[Country].[Country]">
        </dxwpg:PivotGridField>
        <dxwpg:PivotGridField ID="fieldCity1" Area="RowArea" AreaIndex="1" 
            Caption="City"
            FieldName="[Customer].[City].[City]">
        </dxwpg:PivotGridField>
        <dxwpg:PivotGridField ID="fieldCustomerCount" Area="DataArea" AreaIndex="0" 
            Caption="Customer Count"
            FieldName="[Measures].[Customer Count]">
        </dxwpg:PivotGridField>
    </Fields>
</dxwpg:ASPxPivotGrid>

Default.aspx.cs

using System;
using DevExpress.Web.ASPxPivotGrid;

public partial class _Default : System.Web.UI.Page {
    protected void Page_Load(object sender, EventArgs e) {

    }
    string GetPivotStateID(ASPxPivotGrid pivotGrid) {
        return GetType().FullName + "_" + pivotGrid.ID;
    }
    protected void ASPxPivotGrid1_CustomSaveCallbackState(object sender, 
                                  PivotGridCallbackStateEventArgs e) {
        Session[GetPivotStateID((ASPxPivotGrid)sender)] = e.CallbackState;
        e.CallbackState = null;
        e.Handled = true;
    }
    protected void ASPxPivotGrid1_CustomLoadCallbackState(object sender, 
                                  PivotGridCallbackStateEventArgs e) {
        e.CallbackState = (string)Session[GetPivotStateID((ASPxPivotGrid)sender)];
        e.Handled = true;
    }
}

Default.aspx.vb

Imports System
Imports DevExpress.Web.ASPxPivotGrid

Partial Public Class _Default
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    End Sub
    Private Function GetPivotStateID(ByVal pivotGrid As ASPxPivotGrid) As String
        Return Me.GetType().FullName & "_" & pivotGrid.ID
    End Function
    Protected Sub ASPxPivotGrid1_CustomSaveCallbackState(ByVal sender As Object, ByVal e As PivotGridCallbackStateEventArgs)
        Session(GetPivotStateID(DirectCast(sender, ASPxPivotGrid))) = e.CallbackState
        e.CallbackState = Nothing
        e.Handled = True
    End Sub
    Protected Sub ASPxPivotGrid1_CustomLoadCallbackState(ByVal sender As Object, ByVal e As PivotGridCallbackStateEventArgs)
        e.CallbackState = CStr(Session(GetPivotStateID(DirectCast(sender, ASPxPivotGrid))))
        e.Handled = True
    End Sub
End Class