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Posted 24 May 2011


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BitmaskCtrl - Display and edit a number as a bitmask

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4.93/5 (14 votes)
24 May 2011CPOL3 min read
A Windows Forms user control to display and edit numbers as a bitmask.



Configuring hardware often requires to display and edit bitmasks. Modifying a graphical binary representation is usually easier as modifying a hex value in a textbox. A corresponding tooltip could explain the meaning of each single bit and the user gets a much more better feedback to what he is doing.

I was wondering that I didn't find any control around doing this job. Here is my result as a Windows Forms user control.

1. What the BitmaskCtrl demo does

The demo basically displays two BitmaskCtrl instances:

  • A readonly one on the left simply incrementing its own value.
  • A user editable one to the right including a corresponding PropertyGrid intended to play with the BitMaskCtrl properties.

2. BitmaskCtrl readonly mode

  • The BitmaskCtrl displays the bits in a very simple way. Each bit is displayed as a numbered rectangle. Depending on the control's size, the bits get arranged in rows and columns. The colors used for a set/not set bit are configurable.
  • The bits always get laid out in big endian order (in my opinion, a layout in little endian order is not really useful).
  • The control is sizable. It includes an automatic layout function; resize the demo application to explore this. This enables the control to display the value in a vertical orientation.
  • As the Value property is of type UInt64, the maximum bits supported is 64.

3. BitmaskCtrl edit mode

  • The control supports a focus rectangle controlled by mouse moves and by the left/right keys.
  • The focused bit is toggled by a mouse click or the space key.
  • Toggling more than one bit in a single operation is done by dragging over the control with the mouse. The same is possible by keyboard (use the Ctrl/Shift keys and the left/right keys).

Using the code

Reference the BitmaskCtrl like any other control in your own form (as shown in the BitmaskDemo files).

Here is a list of the public BitmaskCtrl properties:

  • public UInt64 Value: Gets or sets the value displayed
  • public int BitCount: Specifies the count of bits to display (usually this depends on the value's datatype)
  • public bool BitMSBFirst: Set to true, if the most significant bit should be displayed first
  • public bool BitStartValue: Set to any offset the least significant bit index should be displayed with (usually 0 or 1)
  • public bool AutoLayout: Set to false to disable the auto layout feature (all bits will be arranged in one single line)
  • public bool ReadOnly: Set to true if the user will not be able to change the displayed value
  • public bool ShowNumbering: Set to false if the bit indices shouldn't be displayed; some of us may use this control as a clavilux :-)
  • public Color BackColor: Specifies the control's back color
  • public Color ForeColor: Specifies the numbering text color to display
  • public Color BitSetColor: Specifies the color used to display a set bit
  • public Color BitNotSetColor: Specifies the color used to display a not set bit
  • public int SelectedIndex: Supplies the currently selected bit index (readonly)

Here is a list of the public BitmaskCtrl events:

  • public event EventHandler SelectedIndexChanged: Selected index changed event, useful to create corresponding tooltips. For example:
  • C#
    void BitmaskCtrl_SelectedIndexChanged(object sender, EventArgs e)
        Console.WriteLine(string.Format("Bit index is {0}"
          , ((BitmaskCtrl)sender).SelectedIndex
  • public event EventHandler ValueChanged: Value changed event. For example:
  • C#
    void BitmaskCtrl_ValueChanged(object sender, EventArgs e)
        Console.WriteLine(string.Format("Value is {0}"
          , ((BitmaskCtrl)sender).Value

Possible extensions to do on the BitmaskCtrl:

  • Replacing the UInt64 value with the BigInteger class from .NET 4.0 may extend the control to support any size of values.

Points of interest

The OnPaint method in a user control is responsible for drawing the complete state of the control. Currently, a LinearGradientBrush is used to do the coloring on the bit rectangles.

To get the best performance in the OnPaint method, the LinearGradientbrush is re-created only if the layout changes.

Maybe you want to modify the drawing code, so do this in BitmaskCtrl.OnPaint(...).


  • 05/24/2011: Initial release.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Joe Nachbaur
Software Developer (Senior) JNnachbaur technical software development
Germany Germany
No Biography provided

Comments and Discussions

GeneralMy vote of 5 Pin
_Vitor Garcia_16-Jul-13 4:45
Member_Vitor Garcia_16-Jul-13 4:45 
GeneralMy vote of 5 Pin
Manoj Kumar Choubey20-Feb-12 21:50
professionalManoj Kumar Choubey20-Feb-12 21:50 
GeneralMy vote of 5 Pin
Filip D'haene24-May-11 5:29
MemberFilip D'haene24-May-11 5:29 

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