Re: How to swap primary key values in a DataTable? - C# Discussion Boards

How to swap primary key values in a DataTable?

24-Jul-03 5:31

Also I'm assuming you're using System.Diagnostics.Process.Start instead of ShellExecute, right?

Cheers,
Tom Archer
Inside C#,
Extending MFC Applications with the .NET Framework
It's better to listen to others than to speak, because I already know what I'm going to say anyway. - friend of Jörgen Sigvardsson

Re: launch & run cmd.exe

nam2324-Jul-03 6:19

nam23

24-Jul-03 6:19

This is my code:

-----------------------------------------
Process commandPrompt = new Process();
commandPrompt.StartInfo.FileName = "C:\\Windows\\System32\\cmd.exe";

//commandPrompt.StartInfo.Arguments = command;
commandPrompt.StartInfo.UseShellExecute = false;
commandPrompt.StartInfo.RedirectStandardInput = true;

commandPrompt.Start();
commandPrompt.StandardInput.WriteLine(command);
-----------------------------------------

I am trying your suggestions - thanks Big Grin | :-D

Radoslav Bielik24-Jul-03 4:35

Radoslav Bielik

24-Jul-03 4:35

Hello,

Is it possible to easily swap values of primary key column between two rows of one DataTable object? I've been trying it like this;

<br />
DataRow dr1=dt.Rows.Find(5); //dt being a DataTable instance<br />
DataRow dr2=dt.Rows.Find(10);<br />
dr1.BeginEdit();<br />
dr2.BeginEdit();<br />
dr1["item_Id"]=10;<br />
dr2["item_Id"]=5;<br />
dr1.EndEdit(); //this will throw an exception, <br />
               //because dr2's PK still has a value of 10<br />
dr2.EndEdit();<br />

Same thing happens with dt.AcceptChanges();
Is there a way how to achieve this? Any clues are highly appreciated!

Rado

Tom Archer24-Jul-03 7:21

24-Jul-03 7:21

DataRow dr1=dt.Rows.Find(5); //dt being a DataTable instance
DataRow dr2=dt.Rows.Find(10);

dr1.BeginEdit();
dr1["item_Id"]=-1; // or any unused value
dr1.EndEdit();


dr2.BeginEdit();
dr2["item_Id"]=5;
dr2.EndEdit();

dr1.BeginEdit();
dr1["item_Id"]=10;
dr2.EndEdit();

dt.AcceptChanges();

Cheers,
Tom Archer
Inside C#,
Extending MFC Applications with the .NET Framework
It's better to listen to others than to speak, because I already know what I'm going to say anyway. - friend of Jörgen Sigvardsson

Radoslav Bielik24-Jul-03 7:33

Radoslav Bielik

24-Jul-03 7:33

Oh thanks a lot! How come this didn't come to my mind Smile | :)

Rado

Tom Archer24-Jul-03 7:37

24-Jul-03 7:37

Because it's common sometimes to overlook the easy stuff in search of the more complex solution. We all do it Wink | ;)

Tom Archer5-Aug-03 12:39

5-Aug-03 12:39

(Repeated from our private email so that others searching for this answer will find it.)

Hi Rado,

Ever have one of those problem that just eats at you? Well your situation has bugged me for some time because I just knew there had to be an easier, more elegant way. There is......

The problem was that BeginEdit calls for the two DataRow objects were disabling the constraints for the respective rows, but once you called EndEdit for one DataRow, the primary key value for that first row conflicted with the (not yet committed) second DataRow object. Therefore, I had to assume that there was a higher level way of turning off constraints - either the DataRowCollection or the DataTable. Finally, I found the DataTable::BeginLoadData and DataTable::EndLoadData method, which turn off and on, respectively, constraint checking and index maintenance for the entire table.

<br />
table.BeginLoadData();<br />
<font color=green>// switch the primary keys for your two DataRow objects</font><br />
table.EndLoadData();<br />

Note: You mentioned the fact that someone suggested turning constraints off for the entire DataSet. As this technicall will work, using BeginLoadData and EndLoadData will affect only one table instead of all the tables for a given DataSet.

Cheers,
Tom Archer
Inside C#,
Extending MFC Applications with the .NET Framework
It's better to listen to others than to speak, because I already know what I'm going to say anyway. - friend of Jörgen Sigvardsson

StealthyMark26-Jul-03 14:50

StealthyMark

26-Jul-03 14:50

Before editing your DataRows, set DataSet.EnforceConstraints to false.

try
{
    dt.DataSet.EnforceConstraints = false;
    // Edit your Rows
    // EndEdit
}
finally
{
    // If you violated any constraints, like PKs,
    // this statement will throw an exception.
    dt.DataSet.EnforceConstraints = true;
}

Generic / Text Only print

Radoslav Bielik27-Jul-03 11:49

Radoslav Bielik

27-Jul-03 11:49

Thanks for the tip!

Rado

MadsJ24-Jul-03 3:13

MadsJ

24-Jul-03 3:13

Hi
We would like to be able to use the different hardware fonts that exists on most printers, when we use the windows driver "Generic / Text Only" *.

We have written some code that enables us to write text to a "Generic / Text Only" (GTO) printer, but despite many attempts we haven't been able to change the font.

For writing text we use the importer legacy function WritePrinter().

Any ideas?

*) We have to use this driver since we also want to use our code for POS printers etc.

Mads

Ista24-Jul-03 6:52

Ista

24-Jul-03 6:52

use the printing events. I cant remember the name but an event rises before it starts a print. you can then query for the selected fonts like a font-family in html

MadsJ24-Jul-03 19:41

MadsJ

24-Jul-03 19:41

Since .NET print any stuff as graphics, the standard .NET printing mechanism doesn't work with a "generic / text only" printer.

Having tried it anyway, we found out that it didn't raise the event (and the code was ok - the event was raised if we choose any other printer).

Personally, I think we have to use some escape sequences - but I haven't been able to find out how to write them.

Thanks for your reply.

Mads

J. Dunlap24-Jul-03 20:13

J. Dunlap

24-Jul-03 20:13

Perhaps you'll have to use the Windows printer API.

"Blessed are the peacemakers, for they shall be called sons of God." - Jesus

"You must be the change you wish to see in the world." - Mahatma Gandhi

Ista25-Jul-03 4:15

Ista

25-Jul-03 4:15

Have you tried crystal reports. I had the same issue with off brand printers. Crystal prints as graphics yes but it can be switched to character printing

Process Monitoring

vikramlinux24-Jul-03 1:56

vikramlinux

24-Jul-03 1:56

Is there any Method/utlity/Class which can help me in process Monitoring? Startup/Exit/busy etc status..

VikramS

Re: Process Monitoring

Tom Archer24-Jul-03 2:18

Create Bitmap and LockBits

24-Jul-03 2:18

Take a look at the System::Diagnostics.Process class:

Exit Notification -> Process.EnableRaisingEvents
Enumerating running processes -> Process.GetProcesses
Finding processes - > Process.GetProcessByName
Alive? -> Process.Responding

That should get you started in the right direction.

Cheers,
Tom Archer
Inside C#,
Extending MFC Applications with the .NET Framework
It's better to listen to others than to speak, because I already know what I'm going to say anyway. - friend of Jörgen Sigvardsson

novachen24-Jul-03 0:51

novachen

24-Jul-03 0:51

Hi! I try to create a target bitmap alike the source bitmap ( in size, in pallete). I hope the target bitmap will be created black(or 0) on every pixel. And then program generate the content of target according to the source one, if some pixel isn't be filled it will be still black.

first trial:

dst = (Bitmap)src.Clone();
BitmapData bmSrcData = src.LockBits(new Rectangle(0, 0, src.Width, src.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
BitmapData bmDstData = dst.LockBits(new Rectangle(0, 0, dst.Width, dst.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
//do some processing on BitmapData

This one work! but it seems clone waste much on copying the content. i wanna it be black, so i have to fill it 0 myself. copy and fill are useless duplicate work.

Second trial:
dst = new Bitmap(src.Width, src.Height, src.PixelFormat);
BitmapData bmSrcData = src.LockBits(new Rectangle(0, 0, src.Width, src.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
BitmapData bmDstData = dst.LockBits(new Rectangle(0, 0, dst.Width, dst.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);

dst will not has the same palette as src. After the process, dst will be a color image even src is a formerly gray one.

Third one:
dst = new Bitmap(src);
BitmapData bmSrcData = src.LockBits(new Rectangle(0, 0, src.Width, src.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
BitmapData bmDstData = dst.LockBits(new Rectangle(0, 0, dst.Width, dst.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);

can't execute! the second LockBits will raise error. anybody know why?

I really puzzled by these methods! any guru can explain what's on earth are these create functions doing? and what's the best way to get my aim?

Re: Create Bitmap and LockBits

leppie24-Jul-03 7:26

leppie

24-Jul-03 7:26

novachen wrote:
can't execute! the second LockBits will raise error. anybody know why?

It appears that dst and src might be the same instance, and thus cannot be locked twice. My guess Poke tongue | ;-P

Unfortunately I cant help you with the others...

leppie ::AllocCPArticle(Generic DFA State Machine for .NET);

how to add component????

don7cry24-Jul-03 0:46

don7cry

24-Jul-03 0:46

How to add my componet in to VS.NET (like that Visual Assist)??
Someone can help me, please!!!
Thanks

function parameter with default value

zecodela23-Jul-03 23:17

zecodela

23-Jul-03 23:17

hi,
i want to know how to make a function including a parameter with default value?
somethings like this...

public void functionA(int A, int B = NULL)
{
// ...
}

any help?

thanks,
jim

monrobot1324-Jul-03 2:37

monrobot13

24-Jul-03 2:37

zecodela wrote:
i want to know how to make a function including a parameter with default value?

As far as I know you can't have default parameters in managed functions.

- monrobot13

Frank Olorin Rizzi24-Jul-03 3:26

Frank Olorin Rizzi

24-Jul-03 3:26

Indeed,
the word I've read everywhere in this regard is that you should use multiple
versions of the member. For ex:
instead of

<br />
public void myFunction(int myInt = 3)<br />
{...}<br />

you should have

<br />
public void myFunction(int myInt)<br />
{<br />
//use myInt as needed<br />
}<br />

AND

<br />
public void myFunction()<br />
{<br />
//use 3 (the default value) as needed<br />
}<br />

Also, you could have one overload call the other:

<br />
public void myFunction(int myInt)<br />
{<br />
//use myInt as needed<br />
}<br />

AND

<br />
public void myFunction()<br />
{<br />
  myFunction(3);<br />
}<br />

HTH,
FOR

Tom Archer24-Jul-03 7:13

24-Jul-03 7:13

Frank is almost correct. You can have functions/methods with default values in some managed languages, but not in C#. His advice on how to circumvent (what I personally see as a) shortcoming in the C# language is correct: Have overloaded versions of the method as follows:

public void foo (int a); // call third foo with default values
public void foo (int a, int b); // call third foo with default values
public void foo (int a, int b, int c);

Cheers,
Tom Archer
Inside C#,
Extending MFC Applications with the .NET Framework
It's better to listen to others than to speak, because I already know what I'm going to say anyway. - friend of Jörgen Sigvardsson