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Hi C# masters,
While I continue my investigation on C#, I'm currently testing some techniques I was used to use in MFC.
I have done the following things:
I derived a UserControl to write my own control. In the OnPaint overridable method, I want to do my drawings. As C# uses GDI+, it's cool, I also use GDI+ in C++.
In MFC I was doing the following thing:
- Instanciate a Bitmap object with the width, height, and color depth
- Link a Graphics object to this bitmap
- Work with this graphic object to generate my bitmap
- When the bitmap was generated, I displayed it on the drawing context.
Therefore, it looks like this
in MFC:
<br />
<br />
...<br />
class CMyWnd : public CWnd<br />
{<br />
...<br />
afx_msg void OnPaint();<br />
...<br />
}<br />
<br />
...<br />
<br />
void CMyWnd::OnPaint()<br />
{<br />
CPaintDC dc(this);<br />
Rect rect;<br />
<br />
GetClientRect((LPRECT) &rect);<br />
<br />
Bitmap bmp(rect.Width, rect.Height, PixelFormat32Bpp);<br />
Graphics memGraphics(&bmp);<br />
Color clr;<br />
<br />
clr.SetFromCOLORREF(::GetSysColor(COLOR_3DFACE));<br />
<br />
SolidBrush brush(clr);<br />
Pen pen(Color::Red);<br />
<br />
memGraphics.FillRectangle(brush, rect);
memGraphics.DrawLine(&pen, rect.X, rect.Y, rect.Width, rect.Height)
<br />
Graphics graphics(&dc);<br />
graphics.DrawImage(&bmp, rect);<br />
}<br />
And there were no flickering while resizing on the fly the derived window 
So, I applied this technique to C#
<br />
protected override void OnPaint(PaintEventArgs e)<br />
{<br />
Bitmap bmp=new Bitmap(ClientRectangle.Width, ClientRectangle.Height);<br />
Graphics memGraphics=Graphics.FromImage(bmp);<br />
Pen pen=new Pen(Color.Red);<br />
Brush brush=new SolidBrush(SystemColors.Control);<br />
<br />
memGraphics.FillRectangle(brush, ClientRectangle);<br />
memGraphics.DrawLine(pen, ClientRectangle.X, ClientRectangle.Y, ClientRectangle.Width, ClientRectangle.Height);<br />
<br />
e.graphics.DrawImage(bmp, ClientRectangle);<br />
}<br />
I remind that the Bitmap object is instancied on both languages to work on a bitmap in memory and once finished, I display the result.
But, in C#, when I resize the control on the fly, there is still flickering 
Can any C# master explain me why???
Thanks.
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First of all, when overriding an event handler like OnPaint, always call the method on the base class (ex, base.OnPaint) unless you have a VERY good reason not too. The base class might have things it needs to do as well, and if you don't the Paint event won't be fired for other, outside classes to handle. Also, whenever you're done with a Bitmap, call Dispose on it or memory consumption increases rapidly. This could be one reason for the flickering. The GC will clean it up eventually, but not in a timely enough manner - especially when the app is busy doing a lot of repainting that occurs when you resize.
Also, for things that don't change - like your Pen, you can store these as fields if time is a big issue, but you should normally dispose those as well.
Finally, you can call SetStyle with ControlStyles.AllPaintingInWmPaint, ControlStyles.DoubleBuffer, and ControlStyles.UserPaint in order to tell the Framework (or rather the underlying system resources) to use double-buffering when painting. This works in most cases.
Microsoft MVP, Visual C#
My Articles
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Hi there,
How can I link a Bitmap object to a Graphics object in C#?
In C++ we can do this:
Bitmap bmp(100, 100, PixelFormat32Bpp);
Graphics memGraphics(&bmp);
How to do the same in C#?
This does not work in C# 
Bitmap bmp(100, 100);
Graphics memGraphics(bmp);
Best regards.
Thanks.
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Graphics.DrawImage()
Mazy
"Art is life, life is life, but to lead life artistically is the art of life." - Peter Altenberg
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yes, but I have do draw lines etc from graphics, in my bitmap....
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Graphics.FromImage(bitmapobject);
Mazy
"Art is life, life is life, but to lead life artistically is the art of life." - Peter Altenberg
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Ok. it works
Thanks.
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hey,
im coding a system in c#...i have got four buttons that link to four diff departments
in the system. these buttons when clicked, opens up the same dialog box which requires a username and
password to access to the respective parts of the system(according to the buttons).
the user name and password is different for each department is it possible for me to use "if else" statements to check
the passwords from the database(SQL).
i've coded in plain english just to check if its logic and possible
private void btnOK_Click(object sender, System.EventArgs e) //ok button on the password dialog box
{
if (btnReg was clicked)
{
check for user name and password in the REG table
if (username and password is correct)
{
allow access
}
else
{
messagebox saying incorrect password
}
}
if (btnDiag was clicked)
{
check for user name and password in the DIAG table
if (username and password is correct)
{
allow access
}
else
{
messagebox saying incorrect password
}
}
}
and so on for the rest of the buttons....
if this is not possible...then is there anyway i can do this...or do i have to code four different password dialog boxes for
each of the buttons which will not be very good for the system, design wise and also extra coding....arrrgghh!! HELP!!
ArvinderGill
Arvinder Singh Gill
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I take it all of the buttons are wired up to the same event?
If so the 'sender' variable is the textbox 'sending' the 'on_click' event. You can then cast the sender variable to a control of type 'textbox'
[code]
TetxtBox txt = (TextBox)s;
[/code]
and evaluate the id etc with either a switch/case statement as below...
[code]
switch(txt.ID)
{
case "ID1":
//Function to check password 1
break;
case "ID2":
//Function to check password 2
break;
case "ID3":
//Function to check password 3
break;
case "ID4":
//Function to check password 4
break;
default:
//Default password failure?
break;
}
[/code]
...or with an If Else statement, that would be up to you. Of course you're password checking could be all nicely wrapped up in it's own class etc.
Hope this is in any way helpful...
Rhys Gravell
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Before showing the dialog, set a property you'd add to the Form that dictates which button was clicked, like an enumeration for example (provides easy value checking to make sure an invalid enumeration wasn't passed in - see Enum.IsDefined).
You could also use a generic prompt Form that has a username and password property that gets the text from their respective TextBox controls in the Form and, if ShowDialog returned DialogResult.OK handle the code in each one of the Click event handlers for the departmental Buttons. If you put this in a terminating loop (for which you can always use break to break out of it if the credentials were authenticated successfully), the dialog could be shown multiple times - even using the same instance. Just don't forget to call Dispose when you're finally done with the Form to free system resources, which is necessary for modal dialogs (i.e., when calling Form.ShowDialog, which has to do with the underlying native resources used by the Form).
There's many other ways you can do this. Personally, I would've invoked the call on some sort of broker since your code to check the database is most likely the same except for, perhaps, the connection string and the query string. If you passed an instance of an object configured with the write departmental connection and query strings, the prompt could simply call a single method and know whether or not the credentials are valid without even knowing which department is authenticating the credentials. After all, it's just a generic prompt dialog - why should it care about how to authenticate credentials. Just use the power of polymorphism. For instance, if you have an interface like so:
public interface IAuthenticator
{
bool Authenticate(string username, string password);
}...and had a property that takes an instance of this interface (by declaring a property of Type IAuthenticator), then when the user tries clicks OK (or Login, or whatever) you make sure this property isn't null and call Authenticate on the instance. Any code that wants to authenticate credentials merely implements this interface and provides a specific implementation of Authenticate. This is a good abstract design.
Microsoft MVP, Visual C#
My Articles
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Hi there,
I’m a long time programmer of C++ and a great fan of the Standard Template Library (STL). I’ve recently started working on C# and find that my beloved vector template doesn’t exist.
To get round the problem of creating a container of class objects I have to implement a whole new class that derives from System.Collections.CollectionBase for the container and then another class to deal with enumeration.
I realise that C# is strongly typed and that is the reason for creating your own containers but does anyone know how I could get round this to create a template class.
Cheers.
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Wait for the next version of C# which includes generics (C# equiv. of templates)... I can hardly contain myself. That is one of the things I miss from C++.
--Colin Mackay--
EuroCPian Spring 2004 Get Together[^]
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
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Thanks for the quick response.
Any idea when C#2.0 is due to be released?
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Colin Angus Mackay wrote:
Wait for the next version of C# which includes generics (C# equiv. of templates)... I can hardly contain myself. That is one of the things I miss from C++.
Yeah me too. Actually, C# generics should be an improvement over our C++ templates; templates are nothing but "exalted macros" as I once read, with the compiler swapping values in at compile time. C# generics will have a JIT'd version of the actual generic code you write, and reuse that JIT'd code across all the types of that generic class.
Fun fun fun stuff. I just hope it will be released in the spring or summer this year.
The graveyards are filled with indispensible men.
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Judah H. wrote:
Actually, C# generics should be an improvement over our C++ templates; templates are nothing but "exalted macros"
Not really.[^]
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You can always use a generic collection or list class like ArrayList. It won't give you strongly-typed params (also, C# isn't strongly-typed, .NET is), but .NET is a true object-oriented framework and adding, for example, a Control to an ArrayList (which accepts Objects) is still a Control in the list. GetType (inheritted from Object) will always return the right Type.
I realize this is probably not what you want and as Colin said, .NET 2.0 (due to release in late 2004 I would imagine, since the end of the year was the release date for 1.0 and 1.1) will include generics. I just wanted to point out that you don't need to worry about using appropriately Typed parameters. After all, when you extend the CollectionBase class and use either List or InnerList (and if you don't, then don't waste time by deriving from CollectionBase), both of those are an instance of the same ArrayList.
Microsoft MVP, Visual C#
My Articles
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You can also use Chris Sells' excellent CollectionGen in the meantime.
http://www.sellsbrothers.com/tools/#collectiongen
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Hi,
my question is how I can make DataGrid whit Button in his title.
for example I want DataGrid whit print button.
I'm ready whit printing part but only a button misсing
thank's.
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You can create a windows control and put a button+datagrid in it or subclass datagrid or datagridcolumn and start from there.
Mazy
"Art is life, life is life, but to lead life artistically is the art of life." Peter Altenberg
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I dont want make DataGridColumnStyle whit buttons.
I want insert button in Caption on DataGrid.
Or mayby I have to make mine control DataGrid+Button //but I dont prefer it.
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Is there any build in functionality to parse standard query string like this:
string1=hello+dear+friend%21&string2=otherdata+here+%25%26
Anything in the framework?
If not I'll write it, should I put it here as an article?
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If you're trying to parse the query string from an ASP.NET page (like an .aspx file), you can use Request.QueryString or Request.Params (combination of POST and GET variables). When getting the value from the parameter dictionary, the values are automatically decoded.
Otherwise, there is many ways this can be parsed, like using String.Split with the &, the doing the same to split the key/value pairs using the = character. The HttpUtility class has both a UrlDecode and UrlEncode method, both overloaded.
Microsoft MVP, Visual C#
My Articles
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