C# Discussion Boards - CodeProject

Shell extensions with C#?

14-Apr-05 22:53

The second question is easy to solve. Handle mouse move and just do a check whether or not the cursor is in the subregion.

The first problem is kind of akward but there are serveral way of solving it. Probably the best way for you is to set up a timer and do frequent checks to see if the Cursor.Position is inside the region. Second is to use a globalhook and every time the mouse moves anywhere on the screen you check (not recommended, native code solution).

Alex Korchemniy

One Stone14-Apr-05 21:09

One Stone

14-Apr-05 21:09

Hello!

How can I write shell extensions with C#? (more specifically: context menu items in explorer)

I'm looking for a nice tutorial like Michael Dunn's excellent article for MFC/C++[^], but using C#. I want to do some real shell programming, not just registry hacks[^]...

Thanks in advance and best regards

Re: Shell extensions with C#?

Wraith215-Apr-05 2:07

Wraith2

15-Apr-05 2:07

It depends which parts of the shell you want to extend, icon handlers and overlays are fairly simple while context menu extensions are rather more tricky. It all requires a reasonable amount of com and win32api interop and some fairly defensive programming to prevent errors reaching and crashing the shell if they occur. Some things like property sheets really aren't possible in fully managed code though that may change when the 2.0 CLR is released.

Paint a region of a panel

sreejeshtr14-Apr-05 19:19

sreejeshtr

14-Apr-05 19:19

I use a panel draw images using graphics.DrawImage(image,x,y,imagewidth,imageheight). This method is called in a foreach loop so that i can fill the panel with different images.Each time panel is refreshed the entire loop executed so that more flickering on the panel.Is there any way to paint a region of a control?

please help!

Alex Korchemniy14-Apr-05 20:10

14-Apr-05 20:10

For a simpler fix consider using double buffering. In the contorl ctor or somewhere else add this:

SetStyle(ControlStyles.DoubleBuffer, true);

A few other options there that you can mess with.

Alex Korchemniy

sreejeshtr14-Apr-05 20:52

sreejeshtr

14-Apr-05 20:52

i 've used it, but itdoesn't make any big difference

thanx for ur reply

Alex Korchemniy14-Apr-05 22:41

14-Apr-05 22:41

Although I'm not exactly sure what you are tyring to do... you can try using your own buffer by using an Image.

Alex Korchemniy

Ashok Dhamija15-Apr-05 0:03

Ashok Dhamija

15-Apr-05 0:03

In case, you are using Invalidate method to refresh the Panel, then instead of using plain Invalidate method, use the following overload of this method, which will refresh a particular rectangular area only:

public void Invalidate(Rectangle rc);

Or, if possible, try to use some bool or other appropriate variable (defined outside the loop but used inside the loop) to somehow check as to in which circumstances and in what rectangular area, the Panel should be refreshed.

If you give details of the method or the manner in which you are refreshing the Panel, it may be possible to give some specific suggestion.

Anonymous15-Apr-05 1:35

Anonymous

15-Apr-05 1:35

private void Panel_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
Graphics g = e.Graphics;
if(myImageArray.Count > 0)
{
foreach (ImageClass myObject in myImageArray)
{
g.DrawImage((Bitmap)myObject.Image,myObject.TopX,myObject.TopY);
}
}
}

this is the code I used in Paint event of Panel
where "ImageClass" contain a bitmap object and its co codinates on the Panel.
"myImageArray" is an ArrayList of type "ImageClass".Each time I click on the panel,a constructor is created with image and Panel's (x,y) co ordinates and its added to myImageArray.
then refresh the Panel.

Control mustn't change it ForeColor to grey, when it is disabled

Mathew Hall14-Apr-05 23:57

Mathew Hall

14-Apr-05 23:57

You'll want to use the Control's Invalidate(Rectangle rc) method (see MSDN[^])

// this will only redraw a 100x100 rectange located <br />
// at the top left corner of the panel<br />
panel.Invalidate(new Rectangle(0, 0, 100, 100));

Then when you paint the panel you only paint an image if its bounding rectangle intersects with the clip rectangle

protected override void OnPaint(PaintEventArgs e)<br />
{<br />
// check if the image intersects with the clip rect<br />
Rectange imageRect = new Rectangle(imageX, imageY, imageWidth, imageHeight);<br />
<br />
if (imageRect.IntersectsWith(e.ClipRectangle))<br />
{<br />
e.Graphics.DrawImage(image, imageRect);<br />
}<br />
}

"I think I speak on behalf of everyone here when I say huh?" - Buffy

Ptmk14-Apr-05 19:17

Ptmk

14-Apr-05 19:17

I want that control (Label, TextBox) with property Enabled = false don't change it ForeColor to grey.
For example I have a UserControl with TextBox or Label on it. I can change TextBox property BackColor very easy:

private void UserControl1_EnabledChanged(object sender, System.EventArgs e)<br />
{<br />
    if(this.Enabled)<br />
    {<br />
    }<br />
    else<br />
    {<br />
        this.TextBox1.BackColor = System.Drawing.Color.White;<br />
    }<br />
}

But I can't change TextBox(Label) property ForeColor!

    private void UserControl1_EnabledChanged(object sender, System.EventArgs e)<br />
    {<br />
        if(this.Enabled)<br />
        {<br />
            this.BackColor = System.Drawing.Color.White;<br />
        }<br />
        else<br />
        {<br />
            this.textBox1.BackColor = System.Drawing.Color.White;<br />
            this.textBox1.ForeColor = System.Drawing.Color.Black;<br />
<br />
            this.Label1.ForeColor = System.Drawing.Color.Black;<br />
        }<br />
    }

This code can't do this!

If I make MyLabel by inheritance of Label and overide OnEnabledChanged(...), this will not help too:

protected override void OnEnabledChanged(EventArgs e)<br />
{<br />
    //base.OnEnabledChanged(e);<br />
}

If I put MyLabel on UserControl1 and then change Enable property of UserControl1 to false, the ForeColor property of MyLabel will not change!
But when I deactivate form with this control and then activate it, text of MyLabel will be grey.

Please, help!

Re: Control mustn't change it ForeColor to grey, when it is disabled

Alex Korchemniy14-Apr-05 20:20

Re: Control mustn't change it ForeColor to grey, when it is disabled

14-Apr-05 20:20

In my humble opinion it is not wise to change the way disabled controls appear to the user. It can confuse people.

If you look into the Label implementation you will see that the disabled appearance of is hardcoded in. You cannot do anything about how a disabled Label looks.

However, if you really need to change something... create your own label implementation.

Alex Korchemniy

spif200114-Apr-05 20:29

spif2001

14-Apr-05 20:29

Some people have problems with monocrome LCD screens, where the text in textBoxes are almost invisible when they have Enabled set to false.

So actually it would be nice to be able to change that color...

Just a point of view.

I'm in the high-fidelity first class traveling set.
And I think I need a Lear jet.

where

alexdg0414-Apr-05 19:15

alexdg04

14-Apr-05 19:15

where i can download the msdn in spanish

Re: where

Disrupted14-Apr-05 19:28

Disrupted

14-Apr-05 19:28

http://www.microsoft.com/spanish/msdn/default.asp[^]

A question on garbage collection

DisruptedSinner14-Apr-05 19:14

DisruptedSinner

14-Apr-05 19:14

Hello everyone,

I have a question on garbage collection that you guys will probably be able to answer in a snap. Here goes...

If I do this...

<br />
public void DoSomethingHere()<br />
{<br />
     MyCustomClass mcc = new MyCustomClass();<br />
     mcc.PerformFunction();<br />
<br />
     mcc = new MyCustomClass();<br />
     mcc.PerformAnotherFunction();<br />
}<br />

As you'll see above, mcc has performed a new twice. I'm just curious as to what happens to the memory from the first "new". Will the garbage collector know about it and clean it up later on, or is this considered a memory leak which will just sit in limbo?

Thanks,
~Brad

spif200114-Apr-05 19:51

spif2001

14-Apr-05 19:51

The garbage collector will pick it up - anything non-static that nobody has a reference to will be picked up.

Disrupted14-Apr-05 19:55

Disrupted

14-Apr-05 19:55

Thank you. Big Grin | :-D

Alex Korchemniy14-Apr-05 20:07

14-Apr-05 20:07

GC will handle it because the first object will no longer be referenced. However be careful with objects that have resources that need to be released.

This makes a big mess:

Bitmap b = new Bitmap(100, 100);<br />
for(int i = 0 ; i < 1000; i++)<br />
{<br />
	b = new Bitmap(100, 100);<br />
}

This is correct:

Bitmap b = new Bitmap(100, 100);<br />
for(int i = 0 ; i < 1000; i++)<br />
{<br />
	b.Dispose();<br />
	b = new Bitmap(100, 100);<br />
}

Alex Korchemniy