DataViewBase.FocusedRowHandleChanging Event

Occurs when the focused row handle is about to change.

Namespace: DevExpress.Xpf.Grid

Assembly: DevExpress.Xpf.Grid.v23.2.Core.dll

NuGet Package: DevExpress.Wpf.Grid.Core

Declaration

C#

public event FocusedRowHandleChangingEventHandler FocusedRowHandleChanging

VB.NET

Public Event FocusedRowHandleChanging As FocusedRowHandleChangingEventHandler

Event Data

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

Property	Description
Handled	Gets or sets a value that indicates the present state of the event handling for a routed event as it travels the route. Inherited from RoutedEventArgs.
NavigationType	Gets the user action that leads to focus change.
NewRowHandle	Gets or sets the handle of the row that gets focus.
OldRowHandle	Gets the handle of the previously focused row.
OriginalSource	Gets the original reporting source as determined by pure hit testing, before any possible Source adjustment by a parent class. Inherited from RoutedEventArgs.
RoutedEvent	Gets or sets the RoutedEvent associated with this RoutedEventArgs instance. Inherited from RoutedEventArgs.
Source	Gets the view that raised this event.

The event data class exposes the following methods:

Method	Description
InvokeEventHandler(Delegate, Object)	When overridden in a derived class, provides a way to invoke event handlers in a type-specific way, which can increase efficiency over the base implementation. Inherited from RoutedEventArgs.
OnSetSource(Object)	When overridden in a derived class, provides a notification callback entry point whenever the value of the Source property of an instance changes. Inherited from RoutedEventArgs.

Remarks

The following code sample does not allow users to focus rows if their CanFocus property is set to false:

C#

private void OnFocusedRowHandleChanging(object sender, FocusedRowHandleChangingEventArgs e) {
    var grid = (GridControl)e.Source.DataControl;
    switch (e.NavigationType) {
        case NavigationType.Prev:
        case NavigationType.Last:
            e.NewRowHandle = GetNextRowHandle(grid, e.NewRowHandle, x => e.Source.GetPrevRowHandle(x)) ?? e.OldRowHandle;
            break;
        case NavigationType.Next:
        case NavigationType.First:
            e.NewRowHandle = GetNextRowHandle(grid, e.NewRowHandle, x => e.Source.GetNextRowHandle(x)) ?? e.OldRowHandle;
            break;
        default:
            e.NewRowHandle = CanFocus(grid, e.NewRowHandle) ? e.NewRowHandle : e.OldRowHandle;
            break;
    }
}
static int? GetNextRowHandle(GridControl grid, int rowHandle, Func<int, int> getNextRowAction) {
    if (rowHandle == DataControlBase.AutoFilterRowHandle || rowHandle == DataControlBase.NewItemRowHandle)
        return rowHandle;
    int nextRowHandle = rowHandle;
    while (grid.IsValidRowHandle(nextRowHandle)) {
        if (CanFocus(grid, nextRowHandle))
            return nextRowHandle;
        nextRowHandle = getNextRowAction(nextRowHandle);
    }
    return null;
}
static bool CanFocus(GridControl grid, int rowHandle) {
    return rowHandle < 0 || ((Item)grid.GetRow(rowHandle)).CanFocus;
}

VB.NET

Private Sub OnFocusedRowHandleChanging(ByVal sender As Object, ByVal e As FocusedRowHandleChangingEventArgs)
    Dim grid = CType(e.Source.DataControl, GridControl)

    Select Case e.NavigationType
        Case NavigationType.Prev, NavigationType.Last
            e.NewRowHandle = If(GetNextRowHandle(grid, e.NewRowHandle, Function(x) e.Source.GetPrevRowHandle(x)), e.OldRowHandle)
        Case NavigationType.[Next], NavigationType.First
            e.NewRowHandle = If(GetNextRowHandle(grid, e.NewRowHandle, Function(x) e.Source.GetNextRowHandle(x)), e.OldRowHandle)
        Case Else
            e.NewRowHandle = If(CanFocus(grid, e.NewRowHandle), e.NewRowHandle, e.OldRowHandle)
    End Select
End Sub

Private Shared Function GetNextRowHandle(ByVal grid As GridControl, ByVal rowHandle As Integer, ByVal getNextRowAction As Func(Of Integer, Integer)) As Integer?
    If rowHandle = DataControlBase.AutoFilterRowHandle OrElse rowHandle = DataControlBase.NewItemRowHandle Then Return rowHandle
    Dim nextRowHandle As Integer = rowHandle

    While grid.IsValidRowHandle(nextRowHandle)
        If CanFocus(grid, nextRowHandle) Then Return nextRowHandle
        nextRowHandle = getNextRowAction(nextRowHandle)
    End While

    Return Nothing
End Function

Private Shared Function CanFocus(ByVal grid As GridControl, ByVal rowHandle As Integer) As Boolean
    Return rowHandle < 0 OrElse (CType(grid.GetRow(rowHandle), Item)).CanFocus
End Function

Refer to the following help topics for more information: Identify Rows and Cards, Iterate Through Rows and Cells in Code.