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ListView.VirtualMode Property

Gets or sets a value indicating whether you have provided your own data-management operations for the ListView control.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

member VirtualMode : bool with get, set

Property Value

Type: System.Boolean
true if ListView uses data-management operations that you provide; otherwise, false. The default is false.

ExceptionCondition
InvalidOperationException

VirtualMode is set to true and one of the following conditions exist:

Setting the VirtualMode property to true puts the ListView into virtual mode. In Virtual mode, the normal Items collection is unused. Instead, ListViewItem objects are created dynamically as the ListView requires them.

Virtual mode can be useful under many circumstances. If a ListView object must be populated from a very large collection already in memory, creating a ListViewItem object for each entry can be wasteful. In virtual mode, only the items required are created. In other cases, the values of the ListViewItem objects may need to be recalculated frequently, and doing this for the whole collection would produce unacceptable performance. In virtual mode, only the required items are calculated.

In order to use virtual mode, you must handle the RetrieveVirtualItem event, which is raised every time the ListView requires an item. This event handler should create the ListViewItem object that belongs at the specified index. In addition, the VirtualListSize property must be set to the size of the virtual list.

Handling the SearchForVirtualItem event enables searching in virtual mode. If this event is not handled, the FindItemWithText and FindNearestItem methods will return a null reference (Nothing in Visual Basic).

You can handle the CacheVirtualItems event in order to maintain a cache of ListViewItem objects. If the calculation or lookup to create a ListViewItem object is expensive, maintaining a cache can improve performance.

If the View property is set to Tile, the value will automatically be changed to LargeIcon when VirtualMode is set to true.

In virtual mode, the Items collection is disabled. Attempting to access it results in an InvalidOperationException. The same is true of the CheckedItems collection and the SelectedItems collection. If you want to retrieve the selected or checked items, use the SelectedIndices and CheckedIndices collections instead.

This example illustrates a simple ListView whose contents are the first ten thousand squares. It handles searching and uses a cache for increased performance.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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