using DevExpress.XtraGrid.Views.Grid;
//...
private void buttonDiscount_Click(object sender, System.EventArgs e) {
    GridView view = gridView1;
    int rowHandle = view.FocusedRowHandle;
    ArrayList rowsToDiscount = new ArrayList();
    //Get related data rows
    if(view.IsGroupRow(rowHandle))
        getChildRows(view, rowHandle, rowsToDiscount);
    else
        rowsToDiscount.Add(view.GetRow(rowHandle));
    //Change the values of the rows
    view.BeginUpdate();
    discount(rowsToDiscount);
    view.EndUpdate();
}

//Returns the child data rows for the given group row
public void getChildRows(GridView view, int groupRowHandle, ArrayList childRows) {
    if(!view.IsGroupRow(groupRowHandle)) return;
    //Get the number of immediate children
    int childCount = view.GetChildRowCount(groupRowHandle);
    for(int i=0; i<childCount; i++){
        //Get the handle of a child row with the required index
        int childHandle = view.GetChildRowHandle(groupRowHandle, i);
        //If the child is a group row, then add its children to the list
        if(view.IsGroupRow(childHandle))
            getChildRows(view, childHandle, childRows);
        else {                    
            // The child is a data row. 
            // Add it to the childRows as long as the row wasn't added before
            object row = view.GetRow(childHandle);
            if(!childRows.Contains(row))
                childRows.Add(row);
        }       
    }
}

//Changes the values of the Price column for the specified rows
public void discount(ArrayList rows) {
    for(int i = 0; i < rows.Count; i++) {
        DataRow row = (rows[i] as DataRowView).Row;    
        decimal oldValue = (decimal)row["Price"];
        row["Price"] = oldValue * 0.95m;               
    }
}

Imports DevExpress.XtraGrid.Views.Grid
'...
Private Sub ButtonDiscount_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles ButtonDiscount.Click
    Dim View As GridView = GridView1
    Dim rowHandle As Integer = View.FocusedRowHandle
    Dim rowsToDiscount As ArrayList = New ArrayList
    'Get related data rows
    If View.IsGroupRow(rowHandle) Then
        getChildRows(View, rowHandle, rowsToDiscount)
    Else
        rowsToDiscount.Add(View.GetRow(rowHandle))
    End If
    'Change the values of the rows
    View.BeginUpdate()
    discount(rowsToDiscount)
    View.EndUpdate()
End Sub

'Returns the child data rows for the given group row
Public Sub getChildRows(ByVal View As GridView, ByVal groupRowHandle As Integer, _
ByVal childRows As ArrayList)
    If Not View.IsGroupRow(groupRowHandle) Then Return
    'Get the number of immediate children
    Dim childCount As Integer = View.GetChildRowCount(groupRowHandle)
    Dim i As Integer
    For i = 0 To childCount - 1
        'Get the handle of a child row with the required index
        Dim childHandle As Integer = View.GetChildRowHandle(groupRowHandle, i)
        'If the child is a group row, then add its children to the list
        If View.IsGroupRow(childHandle) Then
            getChildRows(View, childHandle, childRows)
        Else
            ' The child is a data row. 
            ' Add it to the childRows as long as the row was not added before
            Dim row As Object = View.GetRow(childHandle)
            If Not childRows.Contains(row) Then childRows.Add(row)
        End If
    Next
End Sub

'Changes the values of the Price column for the specified rows
Public Sub discount(ByVal rows As ArrayList)
    Dim i As Integer
    For i = 0 To rows.Count - 1
        Dim row As DataRow = CType(rows(i), DataRowView).Row
        Dim oldValue As Decimal = row("Price")
        row("Price") = oldValue * 0.95
    Next
End Sub

using DevExpress.XtraGrid.Views.Grid;
//...
GridView View = gridView1;
bool expanded = View.GetRowExpanded(view.FocusedRowHandle);
view.SetRowExpanded(view.FocusedRowHandle, !expanded);

Imports DevExpress.XtraGrid.Views.Grid
'...
Dim View As GridView = GridView1
Dim expanded As Boolean = View.GetRowExpanded(view.FocusedRowHandle)
view.SetRowExpanded(view.FocusedRowHandle, Not expanded)

using DevExpress.XtraGrid.Views.Grid;
//...
GridView View = gridView1;
int rowHandle = -1;
do {
    rowHandle = View.LocateByValue(rowHandle+1, View.Columns["Is In Stock"], false);
    View.MakeRowVisible(rowHandle, false);
} while(rowHandle != GridControl.InvalidRowHandle);

Imports DevExpress.XtraGrid.Views.Grid
'...
Dim View As GridView = GridView1
Dim rowHandle As Integer = -1
Do
    rowHandle = View.LocateByValue(rowHandle + 1, View.Columns("Is In Stock"), False)
    View.MakeRowVisible(rowHandle, False)
Loop Until rowHandle = GridControl.InvalidRowHandle