Strange Behavior With BackColor In Inherited Control

[senfo]

I developed a Windows control in VS 2005 that inherits from the
PictureBox Control that adds the ability to select images in a Windows
application. It is, however, experiencing a strange issue that I can't
explain. One of the desired affects was to provide the ability to
change the background color on images that were selected, as well as
setting the background color back to its original color after the image
had been deselected.

To accomplish this task, I added a private member variable
(_originalBackC olor) to remember the background color of the control in
its original, unselected state. The idea was that I could expose a
public property named SelectedBackCol or that I could set BackColor to in
its selected state, then switch back to the unselected color by
assigning the value of _originalBackCo lor back to BackColor for when the
image is unselected.

Sounds simple enough! I determined, however, that the value of
BackColor at the time the constructor is run (which is where I assign
the value of BackColor to _originalBackCo lor), is not the value I
expected. For example, in the designer, I have the background color of
the SelectablePictu reBox set to ControlLightLig ht, which is the same
color I use for the FlowLayoutPanel that hosts the SelectablePictu reBox
control. However, when the constructor is executed, I have determined
that the value of BackColor is *not* ControlLightLig ht, so my
_originalBackCo lor variable is set incorrectly. The visual *appearance*
when the form first loads, however, would lead you to believe that the
SelectablePictu reBox's BackColor were in fact set to ControlLightLig ht,
because it is displayed as white when the form first loads.

The behavior I am experiencing is as follows:

1) Form loads and SelectablePictu reBox appears with desired color
2) Clicking SelectablePictu reBox to select it causes desired selected
background color affect to be applied.
3) Clicking SelectablePictu reBox to unselect it causes the background
color to turn a dark gray instead of the white color that
ControlLightLig ht implies.

The Click event handler is extremely simple:

void pic_Click(objec t sender, EventArgs e)
{
SelectablePictu reBox pic = (SelectablePict ureBox)sender;

if (!pic.IsSelecte d)
{
pic.SelectImage ();
}
else
{
pic.UnSelectIma ge();
}
}

The code for the control is also pretty simple:

using System;
using System.Windows. Forms;
using System.Drawing;

namespace Foo
{
class SelectablePictu reBox : PictureBox
{
private bool _isSelected;
private BorderStyle _selectedBorder Style;
private BorderStyle _originalBorder Style; // Original border
private Color _selectedBackCo lor;
private Color _originalBackCo lor; // Original background color
public delegate void SelectedChanged (object sender, EventArgs e);
public event SelectedChanged OnSelectedChang ed;

/// <summary>
/// Gets or sets a value indicating whether control is selected
/// </summary>
public bool IsSelected
{
get
{
return _isSelected;
}
set
{
_isSelected = value;

// Fire OnSelectedChang ed event
if (OnSelectedChan ged != null)
OnSelectedChang ed(this, new EventArgs());
}
}

/// <summary>
/// Indicates border style for the control when it is selected
/// </summary>
public BorderStyle SelectedBorderS tyle
{
get { return _selectedBorder Style; }
set { _selectedBorder Style = value; }
}

/// <summary>
/// Gets or sets the background color for control when selected
/// </summary>
public Color SelectedBackCol or
{
get { return _selectedBackCo lor; }
set { _selectedBackCo lor = value; }
}

/// <summary>
/// Creates an instance of a SelectablePictu reBox
/// </summary>
public SelectablePictu reBox()
{
this._originalB ackColor = BackColor;
this._originalB orderStyle = BorderStyle;
}

/// <summary>
/// Selects the SelectablePictu reBox
/// </summary>
public void SelectImage()
{
IsSelected = true;
BackColor = SelectedBackCol or;
BorderStyle = SelectedBorderS tyle;
}

/// <summary>
/// Unselects the SelectablePictu reBox
/// </summary>
public void UnSelectImage()
{
IsSelected = false;
BackColor = _originalBackCo lor;
BorderStyle = _originalBorder Style;
}
}
}
Any ideas why I'm experiencing this behavior?

Thank you in advance,

--
Sean

[Peter Ritchie [C# MVP]]

All Designer-configured properties are set in the control's
InitializeCompo nent method. Make sure you save the background colour *after*
the call to InitializeCompo nent.

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"senfo" wrote:

I developed a Windows control in VS 2005 that inherits from the
PictureBox Control that adds the ability to select images in a Windows
application. It is, however, experiencing a strange issue that I can't
explain. One of the desired affects was to provide the ability to
change the background color on images that were selected, as well as
setting the background color back to its original color after the image
had been deselected.

To accomplish this task, I added a private member variable
(_originalBackC olor) to remember the background color of the control in
its original, unselected state. The idea was that I could expose a
public property named SelectedBackCol or that I could set BackColor to in
its selected state, then switch back to the unselected color by
assigning the value of _originalBackCo lor back to BackColor for when the
image is unselected.

Sounds simple enough! I determined, however, that the value of
BackColor at the time the constructor is run (which is where I assign
the value of BackColor to _originalBackCo lor), is not the value I
expected. For example, in the designer, I have the background color of
the SelectablePictu reBox set to ControlLightLig ht, which is the same
color I use for the FlowLayoutPanel that hosts the SelectablePictu reBox
control. However, when the constructor is executed, I have determined
that the value of BackColor is *not* ControlLightLig ht, so my
_originalBackCo lor variable is set incorrectly. The visual *appearance*
when the form first loads, however, would lead you to believe that the
SelectablePictu reBox's BackColor were in fact set to ControlLightLig ht,
because it is displayed as white when the form first loads.

The behavior I am experiencing is as follows:

1) Form loads and SelectablePictu reBox appears with desired color
2) Clicking SelectablePictu reBox to select it causes desired selected
background color affect to be applied.
3) Clicking SelectablePictu reBox to unselect it causes the background
color to turn a dark gray instead of the white color that
ControlLightLig ht implies.

The Click event handler is extremely simple:

void pic_Click(objec t sender, EventArgs e)
{
SelectablePictu reBox pic = (SelectablePict ureBox)sender;

if (!pic.IsSelecte d)
{
pic.SelectImage ();
}
else
{
pic.UnSelectIma ge();
}
}

The code for the control is also pretty simple:

using System;
using System.Windows. Forms;
using System.Drawing;

namespace Foo
{
class SelectablePictu reBox : PictureBox
{
private bool _isSelected;
private BorderStyle _selectedBorder Style;
private BorderStyle _originalBorder Style; // Original border
private Color _selectedBackCo lor;
private Color _originalBackCo lor; // Original background color
public delegate void SelectedChanged (object sender, EventArgs e);
public event SelectedChanged OnSelectedChang ed;

/// <summary>
/// Gets or sets a value indicating whether control is selected
/// </summary>
public bool IsSelected
{
get
{
return _isSelected;
}
set
{
_isSelected = value;

// Fire OnSelectedChang ed event
if (OnSelectedChan ged != null)
OnSelectedChang ed(this, new EventArgs());
}
}

/// <summary>
/// Indicates border style for the control when it is selected
/// </summary>
public BorderStyle SelectedBorderS tyle
{
get { return _selectedBorder Style; }
set { _selectedBorder Style = value; }
}

/// <summary>
/// Gets or sets the background color for control when selected
/// </summary>
public Color SelectedBackCol or
{
get { return _selectedBackCo lor; }
set { _selectedBackCo lor = value; }
}

/// <summary>
/// Creates an instance of a SelectablePictu reBox
/// </summary>
public SelectablePictu reBox()
{
this._originalB ackColor = BackColor;
this._originalB orderStyle = BorderStyle;
}

/// <summary>
/// Selects the SelectablePictu reBox
/// </summary>
public void SelectImage()
{
IsSelected = true;
BackColor = SelectedBackCol or;
BorderStyle = SelectedBorderS tyle;
}

/// <summary>
/// Unselects the SelectablePictu reBox
/// </summary>
public void UnSelectImage()
{
IsSelected = false;
BackColor = _originalBackCo lor;
BorderStyle = _originalBorder Style;
}
}
}
Any ideas why I'm experiencing this behavior?

Thank you in advance,

--
Sean

[Bruce Wood]

You might consider capturing the original background colour in the
OnLoad method, rather in the constructor. I've found that some things
about controls don't quite "settle down" until the control is loaded
and gets a window handle.

That said, you would then have to figure out how to handle the case in
which the caller calls "Select" or "UnSelect" before the control is
first loaded....

senfo wrote:

I developed a Windows control in VS 2005 that inherits from the
PictureBox Control that adds the ability to select images in a Windows
application. It is, however, experiencing a strange issue that I can't
explain. One of the desired affects was to provide the ability to
change the background color on images that were selected, as well as
setting the background color back to its original color after the image
had been deselected.

To accomplish this task, I added a private member variable
(_originalBackC olor) to remember the background color of the control in
its original, unselected state. The idea was that I could expose a
public property named SelectedBackCol or that I could set BackColor to in
its selected state, then switch back to the unselected color by
assigning the value of _originalBackCo lor back to BackColor for when the
image is unselected.

Sounds simple enough! I determined, however, that the value of
BackColor at the time the constructor is run (which is where I assign
the value of BackColor to _originalBackCo lor), is not the value I
expected. For example, in the designer, I have the background color of
the SelectablePictu reBox set to ControlLightLig ht, which is the same
color I use for the FlowLayoutPanel that hosts the SelectablePictu reBox
control. However, when the constructor is executed, I have determined
that the value of BackColor is *not* ControlLightLig ht, so my
_originalBackCo lor variable is set incorrectly. The visual *appearance*
when the form first loads, however, would lead you to believe that the
SelectablePictu reBox's BackColor were in fact set to ControlLightLig ht,
because it is displayed as white when the form first loads.

The behavior I am experiencing is as follows:

1) Form loads and SelectablePictu reBox appears with desired color
2) Clicking SelectablePictu reBox to select it causes desired selected
background color affect to be applied.
3) Clicking SelectablePictu reBox to unselect it causes the background
color to turn a dark gray instead of the white color that
ControlLightLig ht implies.

The Click event handler is extremely simple:

void pic_Click(objec t sender, EventArgs e)
{
SelectablePictu reBox pic = (SelectablePict ureBox)sender;

if (!pic.IsSelecte d)
{
pic.SelectImage ();
}
else
{
pic.UnSelectIma ge();
}
}

The code for the control is also pretty simple:

using System;
using System.Windows. Forms;
using System.Drawing;

namespace Foo
{
class SelectablePictu reBox : PictureBox
{
private bool _isSelected;
private BorderStyle _selectedBorder Style;
private BorderStyle _originalBorder Style; // Original border
private Color _selectedBackCo lor;
private Color _originalBackCo lor; // Original background color
public delegate void SelectedChanged (object sender, EventArgs e);
public event SelectedChanged OnSelectedChang ed;

/// <summary>
/// Gets or sets a value indicating whether control is selected
/// </summary>
public bool IsSelected
{
get
{
return _isSelected;
}
set
{
_isSelected = value;

// Fire OnSelectedChang ed event
if (OnSelectedChan ged != null)
OnSelectedChang ed(this, new EventArgs());
}
}

/// <summary>
/// Indicates border style for the control when it is selected
/// </summary>
public BorderStyle SelectedBorderS tyle
{
get { return _selectedBorder Style; }
set { _selectedBorder Style = value; }
}

/// <summary>
/// Gets or sets the background color for control when selected
/// </summary>
public Color SelectedBackCol or
{
get { return _selectedBackCo lor; }
set { _selectedBackCo lor = value; }
}

/// <summary>
/// Creates an instance of a SelectablePictu reBox
/// </summary>
public SelectablePictu reBox()
{
this._originalB ackColor = BackColor;
this._originalB orderStyle = BorderStyle;
}

/// <summary>
/// Selects the SelectablePictu reBox
/// </summary>
public void SelectImage()
{
IsSelected = true;
BackColor = SelectedBackCol or;
BorderStyle = SelectedBorderS tyle;
}

/// <summary>
/// Unselects the SelectablePictu reBox
/// </summary>
public void UnSelectImage()
{
IsSelected = false;
BackColor = _originalBackCo lor;
BorderStyle = _originalBorder Style;
}
}
}
Any ideas why I'm experiencing this behavior?

Thank you in advance,

--
Sean

[senfo]

Bruce Wood wrote:

You might consider capturing the original background colour in the
OnLoad method, rather in the constructor. I've found that some things
about controls don't quite "settle down" until the control is loaded
and gets a window handle.

That said, you would then have to figure out how to handle the case in
which the caller calls "Select" or "UnSelect" before the control is
first loaded....

That was it, exactly. Thank you very much!

--
Sean