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DataGridView was not designed for data manipulation.
I would suggest you write an SQL query or Stored procedure that uses the MAX function and then call it with the Command.ExecuteScalar() method.
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Quote:
You'll have to teach it how.
Yes , You are Right ! 
in fact I shouldn't to use any database , otherwise , it was simple than i want to do this now !
in any case I should do it with help u !
Regards ! 
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Hi all! I am creating tab pages and adding them to a tab control. When setting the text for a tab page, the part of the tab page where the text is shown always stretches to show the full tab page title. But some of the titles are very long and would like to know how I can limit the width of the part of the control where the title is shown so that not all characters will be shown. I think this will enable the tab control to show more tab page titles at a time. Thanks in advance.
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In a TabControl the functionality of the tabs themselves is very limited.
You have basically two choices:
1. create your own TabControl, giving you lots of headaches and full control.
2. modify the TabPage texts in accordance to the page being selected or not (that is what I would do). You could store the long and short texts in two separate Dictionary<TabPage,string> collections, and use the SelectedIndexChanged event to apply them.
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Here's the way I would approach this: assuming this is WinForms: and, assuming that I wanted all the tabs to always maintain a certain short length
... of course Luc's excellent solution (above) would work great if you are willing to change the width of the TabPage Tab header text when each TabPage is selected ...
1. on the TabControl: set the 'ShowToolTips property to 'true
2. for each Tab:
a. define a short, hopefully mnemonic, name for the Tab
b. set the ToolTipText for that Tab to the longer name
3. fill each TabPage with a Panel with its 'Dock property set to 'Fill
Discussion: The Panel that fills each TabPage will not show a ToolTip, but mouse-over the Tab will show the "long name."
One step further using this suggestion: I suppose if I had a lot of Tabs ... or for future flexibility in revision/maintenance ... I might "automate" this by creating two matching Lists, or a Dictionary, and then, in the Form's 'Load EventHandler, doing the right thing to set each TabPage's 'Text and 'ToolTipText properties in a loop.
The Occam's Razor solution: Perhaps the simplest, idea of all, if you are willing to use the content area of the TabPage: put a label somewhere on each TabPage showing the full-name.
Thinking out-of-the-box: create a UserControl that joins a TabControl with a StatusStrip control, and show the full name, and whatever else, in the StatusStrip for each selected TabPage ?
"... Sturgeon's revelation. It came to him that Science Fiction is indeed ninety-percent crud, but that also—Eureka!—ninety-percent of everything is crud. All things—cars, books, cheeses, hairstyles, people and pins are, to the expert and discerning eye, crud, except for the acceptable tithe which we each happen to like." early 1950's quote from Venture Sci-Fi Magazine on the origin of Sturgeon's Law, by author Theodore Sturgeon: source Oxford English Dictionary on-line "Word-of-the-Day."
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Hi All !
Is it possible to Naming "Row" of A DataGridView as a Column "Header Text" .
Thanks a Lot !
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I'm not sure what you mean, but how about System.Windows.Forms.DataGridViewRowHeaderCell.Value ?
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yes , but Not For Rows , I don't think exist any property for Row to put a Text !
Thanks !
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Then explain more clearly what you want.
System.Data.DataTable dt = new System.Data.DataTable() ;
for ( int col = 0 ; col < 10 ; col++ )
{
dt.Columns.Add ( new System.Data.DataColumn ( col.ToString() ) ) ;
}
for ( int row = 0 ; row < 10 ; row++ )
{
System.Data.DataRow dr = dt.NewRow() ;
for ( int col = 0 ; col < dt.Columns.Count ; col++ )
{
dr [ col ] = row * col ;
}
dt.Rows.Add ( dr ) ;
}
this.dataGridView1.DataSource = dt ;
for ( int row = 0 ; row < dt.Rows.Count ; row++ )
{
this.dataGridView1.Rows [ row ].HeaderCell.Value = row.ToString() ;
}
This gives me a DataGridView showing a multiplication table with the row headers showing the row number.
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thanks for Ur Help , I wanted To give A Name for Each Row , that stored in a Combo Box !
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How about you adding a DataGridViewColumn which would then hold the names you choose?
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Hello all,
I am currently handling very large images, which are basically generated by stitching together many smaller images (e.g. panorama or photo mosaic software). In order to avoid out-of-memory exceptions (in memory are only "maps" of how to arrange the smaller images), I wrote some code saving these images line by line as bitmaps using BinaryWriter and LockBits. So far, so good.
The problem is now that I would like to save these images as Jpegs (or PNGs) as well. Since I am pretty new to c# I can only think of two ways for now:
1) Similar to the bitmap saving procedure. Generating some jpeg header and saving the big images line by line, compressing them somehow before. I have no idea how to perform the compression though.
2) Streaming the already saved bitmap into the memory and saving it as encoded jpeg.
Since the second approach seemed easier, I tried something like this:
FileStream fsr = new FileStream("input.bmp", FileMode.Open, FileAccess.Read);
FileStream fsw = new FileStream("output.jpg", FileMode.CreateNew, FileAccess.Write);
EncoderParameters encoderParameters = new EncoderParameters(1);
encoderParameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 80L);
Bitmap bmp = new Bitmap(fsr);
bmp.Save(fsw, GetEncoder(ImageFormat.Jpeg), encoderParameters);
bmp.Dispose();
The problem is now that the save-method tries to completely load the bitmap into memory first, causing an out-of-memory exception.
I would be more than happy for any suggestions on how to solve or circumvent this problem!
Cheers,
Max
Update: I now edited the code so that it saves bands of 8 lines as bmp. These bands I would now like to save to the same jpeg file - any ideas?
modified 24-Nov-11 8:04am.
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Well, that's what it does. A third party encoder may be worth looking into, or you can roll your own. PNG is pretty easy to encode in a streaming way (the Deflate step obviously requires a buffer, but a constant-size small one). JPG of course can't exactly be encoded line-by-line, but block by block isn't any worse.
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You can't get decent JPEG compression for images with insufficient height, the DCT step in the JPEG compression algorithm is using pixel blocks of 8 by 8 pixels. Any less will fail terribly.
Are you sure you are actually running out of memory? How many elementary images are there, and what is their size?
The reason I ask is GDI+ tends to be pretty confusing with its error messages, e.g. when Image.FromFile() says "out-of-memory" it really means "this is an image format I don't understand". See here[^].
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@darkDercane: Yes, I would like to compress it. The problem is that I do not know how to do this chunk by chunk.
@harold aptroot: Do you by chance know of any example on how to encode (and save) a picture block-by-block?
@Luc Pattyn: It would be no problem to hand the compression algorithm blocks of 8x8 pixels, I chose to do it linewise for no real reason. Assuming that I deliver chunks of 8x8 or bigger, how can I encode these chunks into one JPG (or PNG) file?
And yes, I am pretty sure, I am really running out of memory. The filesize of each elementary image is about 10k px (e.g. 100x100), there could be sth like10 to 100k of them in the final image. I recently tested the program by saving the resulting image on hdd and got a 1.7 GB (32bpp) bmp monster image file. I do not plan to exceed the 32kpx limit of bmp though.
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I have several small programs that scrap input and load it into a database. Since much of the code relies on external resources being ready, a lot of my code ends up being in try/catch blocks. Is there a lot of overhead associated with these? I have tried to consolidate interaction with external sites and db's so there are a minimal number.
Is there a better way to do this than having a block in each method?
Thx
Mark Jackson
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IMO if a condition can be expected and tested for then it is not an exception and you shouldn't rely on exception handling.
No comment
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Yes, but on some other hand somewhere... continually testing for a rare state wastes cycles.
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Agreed. There is a difference between rare, unexpected conditions and common, expected conditions.
PIEBALDconsult wrote: some other hand somewhere
Did you forget where your other hand went? Or are you using someone else's hand? 
No comment
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IMO you should stay away from religious arguments.
By the time you're finished checking all the conditions, I could have the deleted the file that you're reading.
Bastard Programmer from Hell 
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This.
Writing "bullet proof" code that handles every case from day one, I've learned is a waste of your time and CPU cycles and does nothing but piss off your boss who is wondering why it is taking you so long. Write your first pass with general case error handling and add the obscure corner cases as you come across them in testing.
However, structuring your code with the intention of handling these corner cases down the road would behoove you.
What I mean by that is... well, one of the projects I'm working on is a project that my boss implemented 100%, and he is "from the street" and doesn't believe in structure and design, so there is SQL code sprinkled pretty much every where. Had he packaged all his SQL code into a single DAL, it would have been much easier to debug and expand. The project that I wrote 100% from scratch, I did exactly that... yeah, it didn't handle every corner case from day one, but as I found the cases, I only had to change 1 or 2 places.
I'm mentioning this because it sounds like you have your external access stuff sprinkled everywhere throughout the GUI .
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Indeed, where it's appropriate, a simple check can often save time. Ultimately, as you progress, you end up building a handy set of utility methods that you can use, for instance here's a simplified version of a file create that you could use:
public static FileStream TryCreateFile(string fileToCreate)
{
string directoryName = Path.GetDirectoryName(fileToCreate);
if (!Directory.Exists(directoryName))
Directory.CreateDirectory(directoryName);
return File.Create(fileToCreate);
}
modified 23-Nov-11 15:33pm.
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How does that save time? Delete will check for the existence of the file a second time.
Edit: Or is that just a bad example?
"If the file to be deleted does not exist, no exception is thrown."
modified 23-Nov-11 15:20pm.
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