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DockLayoutManager.MDIMergeStyle Property

Gets or sets if and when the merge mechanism is invoked by the DockLayoutManager.

Namespace: DevExpress.Xpf.Docking

Assembly: DevExpress.Xpf.Docking.v23.2.dll

NuGet Package: DevExpress.Wpf.Docking


public MDIMergeStyle MDIMergeStyle { get; set; }

Property Value

Type Description

An MDIMergeStyle enumerator value that specifies if and when the merge mechanism is invoked.

Available values:

Name Description

Identical to the MDIMergeStyle.Always value.


Bars/ribbons are merged in the following cases:

  • When you activate a maximized MDI child panel (MDI UI).
  • When you select a tab (tabbed UI).

Bars/ribbons are unmerged in the following cases:

  • When you restore a maximized MDI child panel from the maximized to the normal state or deactivate it (MDI UI).
  • When you deactivate a selected tab or select another tab (tabbed UI).

The panel’s bar/ribbon is merged with the parent bar/ribbon in the following cases:

  • When you maximize a DocumentGroup‘s MDI child panel (MDI UI).
  • When you select the DocumentGroup‘s panel in the tab (tabbed UI).

If your layout contains multiple DocumentGroups, the merging mechanism is invoked for all DocumentGroups simultaneously. In this case, all of them are merged to the parent at the same time.

Bars/ribbons are unmerged in the following cases:

  • When you restore an MDI child panel from the maximized state to the normal state (MDI UI).
  • When you select another tab (Tabbed UI).

Prevents all child tabbed and MDI panels from being merged.


Similar to WhenChildActivated mode, but additionally merges MDI panels and tabs that are initially maximized (docked), but not yet selected (for example, on application start).


A DockLayoutManager supports merging Bars, RibbonControls and RibbonStatusBarControls of child panels with the main panel’s Bars, RibbonControls and RibbonStatusBarControls. In regular MDI mode, by default, these controls are merged when a child MDI panel is maximized. In tabbed MDI mode, (when the host group’s DocumentGroup.MDIStyle property is set to Tabbed), the merging is performed when a tab is activated. Selecting another tab unmerges the previous tab and merges the newly selected one.

The MDIMergeStyle property allows you to specify when the merging/unmerging mechanism is invoked. This property is applied to all child panels within the current DockLayoutManager. Use the DocumentPanel.MDIMergeStyle property to override this setting for individual panels.

It is also possible to prevent Bars, RibbonControls or RibbonStatusBars from being merged by setting the BarManager.MDIMergeStyle, RibbonControl.MDIMergeStyle or RibbonStatusBarControl.MDIMergeStyle property to MDIMergeStyle.Never.

The following code shows how to restrict merging for one specified panel and allow it for all the others:


<dxdo:DockLayoutManager x:Name="dockManager" MDIMergeStyle="Always">
        <dxdo:DocumentGroup Name="mdiContainer" MDIStyle="MDI">
            <dxdo:DocumentPanel Name="unmergedPanel"
                                Caption="This Panel Never Invokes The Merging Mechanism"
                                MDISize="500,300" />
            <dxdo:DocumentPanel Name="mergedPanel"
                                Caption="This Panel Is Merged When Maximized"
                                MDISize="500,300" />
See Also