ASPxTabControlBase.ActiveTabChanged Event

Fires on the server side after the active tab has been changed within a tab control.

Namespace: DevExpress.Web

Assembly: DevExpress.Web.v20.2.dll

NuGet Package: DevExpress.Web

Declaration

C#

public event TabControlEventHandler ActiveTabChanged

VB.NET

Public Event ActiveTabChanged As TabControlEventHandler

Event Data

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

Property	Description
Tab	Gets a tab object related to the event.

Remarks

Write an ActiveTabChanged event handler to perform actions on the server side each time the selected tab is changed. You can use the event parameter’s Tab property to identify the new active tab.

When a user changes the active tab, a control (ASPxTabControl or ASPxPageControl) might raise the following events:

• On the server side:
  • ASPxTabControlBase.ActiveTabChanged
  • ASPxTabControlBase.ActiveTabChanging
• On the client side:
  • ASPxClientTabControlBase.ActiveTabChanged
  • ASPxClientTabControlBase.ActiveTabChanging

The following two properties control which events to generate:

• the AutoPostBack property of a control
• the processOnServer property of the client-side ActiveTabChanging event argument

Note

The processOnServer property’s default value is equal to a control’s AutoPostBack property setting.

The value of the AutoPostBack property affects the event generation logic as follows:

• true: Only the server-side ActiveTabChanging and ActiveTabChanged events are raised. Their client-side equivalents (ActiveTabChanging and ActiveTabChanged) are not invoked.

• false: The default behavior is that the client-side ActiveTabChanging and ActiveTabChanged events are raised to handle an active tab change only on the client. Optionally, you can pass event processing to handlers of the server-side event equivalents (ActiveTabChanging and ActiveTabChanged). To do this, enable the processOnServer property in a client-side ActiveTabChanging event handler. Note that the client-side ActiveTabChanged event is not fired in this case.

Example: Use AutoPostBack to Handle Events on the Server

This example enables the AutoPostBack property to make a control process ActiveTabChanging and ActiveTabChanged events on the server.

ASPX

<dx:ASPxLabel ID="ActiveTabLabel" runat="server"/>
<dx:ASPxCheckBox ID="AllowTabChange" runat="server" Text="Allow Tab Change" Checked="True" CheckState="Checked"/>
<dx:ASPxTabControl ID="TabControl" runat="server" 
                   AutoPostBack="True"
                   OnActiveTabChanging="TabControl_ActiveTabChanging"
                   OnActiveTabChanged="TabControl_ActiveTabChanged">
  <Tabs>
    <dx:Tab Text="Tab1"/>
    <dx:Tab Text="Tab2"/>
    <dx:Tab Text="Tab3"/>
  </Tabs>
</dx:ASPxTabControl>

C#

protected void TabControl_ActiveTabChanging(object source, DevExpress.Web.TabControlCancelEventArgs e){
    //Based on the checkbox state, specify whether to cancel the tab change.
    e.Cancel = !AllowTabChange.Checked;
}

protected void TabControl_ActiveTabChanged(object source, DevExpress.WebTabControlEventArgs e){
    //Display the name of the active tab.
    ActiveTabLabel.Text = $"Active Tab: {e.Tab.Text}";
}

Example: Use processOnServer to Pass Event Handling to the Server

This example shows how to make a control with the disabled AutoPostBack property generate the server-side ActiveTabChanging and ActiveTabChanged events. Enable the processOnServer property in a client-side ActiveTabChanging event handler to pass event processing to the server.

ASPX

<dx:ASPxLabel ID="ActiveTabLabel" runat="server"/>
<dx:ASPxCheckBox ID="AllowTabChange" runat="server" Text="Allow Tab Change" Checked="True" CheckState="Checked"/>
<dx:ASPxTabControl ID="TabControl" runat="server"  
    OnActiveTabChanging="TabControl_ActiveTabChanging" 
    OnActiveTabChanged="TabControl_ActiveTabChanged"
    AutoPostBack="False">
    <Tabs>
        <dx:Tab Text="Tab 1"/>
        <dx:Tab Text="Tab 2"/>
        <dx:Tab Text="Tab 3"/>
    </Tabs>
    <ClientSideEvents ActiveTabChanging="function(s, e) {
        //Pass tab change processing to the server.
        e.processOnServer = true;
    }" />
</dx:ASPxTabControl>

C#

protected void TabControl_ActiveTabChanging(object source, DevExpress.Web.TabControlCancelEventArgs e){
    //Based on the checkbox state, specify whether to cancel the tab change.
    e.Cancel = !AllowTabChange.Checked;
}

protected void TabControl_ActiveTabChanged(object source, DevExpress.Web.TabControlEventArgs e){
    //Display the name of the active tab.
    ActiveTabLabel.Text = $"Active Tab: {e.ActiveTab.Text}";
}