NumericUpDown extended control
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If you have ever written a data-entry application, there's a big chance you used NumericUpDown control. This control is great to provide a field to enter numeric values, with advanced features like up-down buttons and accelerating auto-repeat.
The other side of the coin is that
NumericUpDown is not really mouse-aware. I experienced some bugs and bad behaviors:
- I need to select all the text when it gets focus (see below), but it misses some of the
AutoSelectproperty will be useful).
- Some of the standard events are not working properly (see below):
- Rotating the mouse wheel when the control is focused causes its value to change. A property to change this behavior, like
InterceptArrowsKeysfor up/down keys, will be useful.
That's why I decided to subclass it, fixing these points and adding missing features and properties.
Note: this control has been published on CodeProject.
Missing TextBox properties
I needed some missing
TextBox properties when I was asked to select all the text in the control when it got the focus.
NumericUpDown exposes a
Select(int Start, int Lenght) method you can call to select all text. At first try, I attached to the
GotFocus event to call
Select(0, x) but, hey, wait a moment... what should I use for x? It seems that any value is accepted, even if greater than the text length. OK, let's say x=100 and proceed. This works well with the keyboard focus keys (like TAB), but it's completely useless with the mouse: a mouse click raises the
GotFocus event (where I select all the text), but as soon as you release the button, a zero-selection is done, leaving the control with no selection. OK, I thought, let's add a
SelectAll on the
MouseUp event too, but this way, the user cannot perform a partial selection anymore; each time the mouse button is released, all the text is selected. I need to know if a partial selection exists; in a
TextBox, I can test it with
SelectionLength > 0, so I need to access the underlying
Now comes the tricky part:
NumericUpDown is a composite control, a
TextBox and a button box. Looking inside it through the Reflector, we can find the internal field which holds the textbox part:
Friend upDownEdit As UpDownEdit ' UpDownEdit inherits from TextBox
We'll obtain a reference to this field using Reflection; this is done in the control creator.
''' <summary> ''' object creator ''' </summary> Public Sub New() MyBase.New() ' extract a reference to the underlying TextBox field _textbox = GetPrivateField(Of TextBox)(Me, "upDownEdit") If _textbox Is Nothing Then Throw New ArgumentNullException(Me.GetType.FullName & ": Can't find internal TextBox field.") End If ' extract a reference to the underlying UpDownButtons field _upDownButtons = GetPrivateField(Of Control)(Me, "upDownButtons") If _upDownButtons Is Nothing Then Throw New ArgumentNullException(Me.GetType.FullName & ": Can't find internal UpDown buttons field.") End If ' add handlers (MouseEnter and MouseLeave events of NumericUpDown ' are not working properly) AddHandler _textbox.MouseEnter, AddressOf _mouseEnterLeave AddHandler _textbox.MouseLeave, AddressOf _mouseEnterLeave AddHandler _upDownButtons.MouseEnter, AddressOf _mouseEnterLeave AddHandler _upDownButtons.MouseLeave, AddressOf _mouseEnterLeave AddHandler MyBase.MouseEnter, AddressOf _mouseEnterLeave AddHandler MyBase.MouseLeave, AddressOf _mouseEnterLeave End Sub ''' <summary> ''' Extracts a reference to a private underlying field ''' </summary> Protected Friend Shared Function GetPrivateField(Of T As Control) _ (ByVal ctrl As NumericUpDownEx, ByVal fieldName As String) As T ' find internal TextBox Dim fi As Reflection.FieldInfo _ = GetType(NumericUpDown).GetField(fieldName, _ Reflection.BindingFlags.FlattenHierarchy _ Or Reflection.BindingFlags.NonPublic _ Or Reflection.BindingFlags.Instance) ' take some caution... they could change field name in the future! If fi Is Nothing Then Return Nothing Else Return TryCast(fi.GetValue(ctrl), T) End If End Function
Now that we have the underlying
TextBox, it is possible to export some missing properties:
<browsable(false)> _ <designerserializationvisibility( _=""> _ Public Property SelectionStart() As Integer Get Return _textbox.SelectionStart End Get Set(ByVal value As Integer) _textbox.SelectionStart = value End Set End Property</designerserializationvisibility(></browsable(false)>
And finally, we can have a perfectly working mouse management:
' MouseUp will kill the SelectAll made on GotFocus. ' Will restore it, but only if user have not made ' a partial text selection. Protected Overrides Sub OnMouseUp(ByVal mevent As MouseEventArgs) If _autoSelect AndAlso _textbox.SelectionLength = 0 Then _textbox.SelectAll() End If MyBase.OnMouseUp(mevent) End Sub
Mouse events not raised properly
MouseLeave events are raised in couples: a
MouseEnter immediately followed by a
MouseLeave. Maybe that's why, to discourage their use, they are marked with a
<browsable(false)> attribute. Since I need the
MouseEnter event to update my
StatusBar caption, I investigated a little on this "bug".
As said above,
NumericUpDown is a composite control (red rectangle in the following picture) containing a
TextBox (left green rectangle) and some other controls:
The "control" area is the one between the red and the green rectangles; when you fly over it with the mouse, you'll receive the
MouseEnter event while between the red and the green, then
MouseLeave when inside the green rectangle. The same happens when you leave.
The better way to raise these events, now that we can access the underlying
TextBox, is to re-raise the
MouseLeave events as raised from the
TextBox itself; this is what
NumericUpDown's management of the mouse wheel is, sometimes, really annoying. Suppose you have an application which displays some kind of chart, with a topmost dialog (toolbox) to let the user change some parameters of the graph. In this dialog, the only controls which can keep the focus are
After your user puts the focus inside one of them, the mouse wheel is captured by the
NumericUpDown. When the user wheels to, say, scroll the graph, the effect is that the focused field value is changed; this behavior is really annoying.
A fix could be to kill the
WM_MOUSEWHEEL message for the control, but this will kill even "legal" wheelings.
NumericUpDown has a property which allows
WM_MOUSEWHEEL messages to pass only if the mouse pointer is over the control, making sure that the user is wheeling to change the control value.
This is done by keeping track of the mouse state in the
MouseEnter-MouseLeave events, then killing
WM_MOUSEWHEEL messages accordingly.
Up-Down buttons visibility
You can hide Up and Down buttons box when the mouse is not over the control.
To achieve this, set the
ShowUpDownButtons property to
WhenMouseOver instead of
How to use the control
Simply compile sources and include NumericUpDownEx.vb in your project, using the control like you'll do with the standard
You could also directly include its source code into your project, avoiding the deployment of an additional DLL.
v1.4 - 2012-12-17
- New option to show up/down buttons when the control has focus (regardless of mouseover), thanks to Fred Kreppert for his suggestion.
v1.3 - 2010-03-15
- Added new property: when set, if Maximum is reached during an increment, Value will restart from Minimum (and vice versa)
(feature suggested by YosiHakel here)
- Cleaned up the C# version
v1.2 - 2010-02-10
- Added two new events BeforeValueDecrement and BeforeValueIncrement, as suggested by andrea@gmi.
This will allow to give different increment/decrement depending on current control value
- Added a C# version of the control to the ZIP
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