Visual Basic

22-Feb-07 4:12

Im unsure where I should place the code for closing, flushing, and disposing of the various readers and writers.

Currently I place the .Flush and .Close inside the try block right before the Catches and then I place the .Dispose calls inside the Finally.

Cleako

Dave Kreskowiak22-Feb-07 6:05

22-Feb-07 6:05

Normally, you'd place the .Flush/.Close and .Dispose in the Finally block. You'd first check to see that the stream is indeed open before you called Close on it, then Dispose it.

Why? Because your code could throw an exception before or during the file open, so it's possible that the file never gets opened. Also, it's possible that your code could throw an exception during the manipulation of the file, leaving the file hung open in the Catch/Finally handlers. Finally gets executed no matter what happens in the Try block, so checking and closing the file in the Finally block is the best place to do it.

Dim sw As StreamWriter
Try
    sw = New StreamWriter(filePath)
    For x As Integer = 1 to 100
        sw.WriteLine(x)
    Next
Catch ex As Exception
    ' used a 'catch all' Exception which is not really good practice!!
Finally
    ' You'll only get a StreamWriter object if the file was successfully opened!
    If Not sw Is Nothing Then
        sw.Close()
        sw.Dispose()
    End If
End Try

Now in place of that, with VB.NET 2005, you can instead use the Using keyword to do the same thing. When the code execution leaves the Using block for any reason the object created on the Using line is automatically closed Disposed.

Try
    Using sw As StreamWriter = New StreamWriter(filePath)
        For x As Integer = 1 to 100
            sw.WriteLine(x)
        Next
    End Using
Catch ex As Exception
    ...
End Try

Dave Kreskowiak
Microsoft MVP - Visual Basic

Marcus J. Smith22-Feb-07 6:21

22-Feb-07 6:21

Does that take care of the flush and everything? If I have multiple writers would it make a difference to have all of those nested?

Cleako

Dave Kreskowiak22-Feb-07 6:25

22-Feb-07 6:25

cleako wrote:
Does that take care of the flush and everything?

Disposing a StreamWriter, or any file stream for that matter, automatically calls Flush and Close.

Dave Kreskowiak
Microsoft MVP - Visual Basic

Marcus J. Smith22-Feb-07 6:28

22-Feb-07 6:28

If I have, say 5 writers, to write to 5 files depending on a condition, if I use the keyword Using and I create all 5 is there a way to avoid that indenting?

Cleako

Dave Kreskowiak22-Feb-07 6:56

22-Feb-07 6:56

If you're writing to all 5 files for each record you write, no there isn't unless you turn off the automatic formatting in Tools/Options. But do that also turns off the formatting for every file in every project you open from then on.

If your picking which file you are going to write to for each record, then create a StreamWriter when you need to write to that particulare file. Don't open the file(s) unless you need to write to it. But, there is a performance penality for doing this, so you might want to test it before you nail it down as production code. But, if you sacrifice performance just to make the code "look pretty", I'll frown up you if you ever end up on my team...

Basically, no there isn't. It's not so bad. I've seen C++ and C# code indented 20-30 levels deep because of nested IF's and loops. It happens...

Dave Kreskowiak
Microsoft MVP - Visual Basic

Marcus J. Smith22-Feb-07 7:13

22-Feb-07 7:13

You're saying there is a performance hit to open the file everytime you need to write to it or to open 5 and write if you need to when you need to until you are done and then closing them all?

Also, checking for nothing establishes if it is ok to Flush and Close?

One more, Smile | :)

, are you saying I could simply call .Dispose and it would take care of the Flush/Close instead of me calling those 2 in addition to the .Dispose?

Cleako

Dave Kreskowiak22-Feb-07 7:28

22-Feb-07 7:28

cleako wrote:
You're saying there is a performance hit to open the file everytime you need to write to it or to open 5 and write if you need to when you need to until you are done and then closing them all?

Yes, there is a performance penalty for opening and closing a file. Try it. Write a little app that opens a file, writes 10,000 lines of text to it, then closes it. Then rewrite that loop so it opens the file, writes a line to it, then closes it, 10,000 times. See which one runs faster.

cleako wrote:
checking for nothing establishes if it is ok to Flush and Close?

You're checking to see if it is safe to call Flush and Close, and even Dispose, on that object. If that object is Nothing, then any call you make on it will result in a Null Reference Exception.

cleako wrote:
are you saying I could simply call .Dispose and it would take care of the Flush/Close instead of me calling those 2 in addition to the .Dispose?

Yep.

Dave Kreskowiak
Microsoft MVP - Visual Basic

RAR

Navneet Hegde22-Feb-07 2:22

Navneet Hegde

22-Feb-07 2:22

Dear All,

I have a file which is archived with RAR and Password protected now I simply can't get it way. Is there any way to get its data as it's really required.

Develop2Program & Program2Develop

Re: RAR

Dave Kreskowiak22-Feb-07 4:17

Setup Project won't build/re-build

22-Feb-07 4:17

What does this have to do with VB.NET???

You have to have the password to open the RAR since the data is encoded with it. You can probably try Googling for some cracking tools, but don't get your hopes up.

Dave Kreskowiak
Microsoft MVP - Visual Basic

HamCoder22-Feb-07 1:52

HamCoder

22-Feb-07 1:52

I am running VB.NEt(2003). I have a solution with 2 projects - the True project and the Setup project. User documentation is in a Help directory which contains 29 htm, bmp, and ico files. A year ago, both projects were fine and Setup project successfully deployed to several computers. I've completed some maintenance to the True project, which compiles and tests OK in Debug mode.

When I change to Release mode, the Setup project will not compile. It seems to make no difference whether I click Build or Rebuild for either the Setup project or the Solution.

Sometimes I get this error message

C:\Development\VBN\VAQSO\VAQSO_Setup\VAQSO_Setup.vdproj Could not find file 'C:\Program Files\Microsoft Visual Studio .NET 2003\Common7\Tools\Deployment\.\MsiRedist\1033\MsiLoadr.Bin' 'Interface not registered'

Note the \.\ in the middle. The file & path (without the period) exist.

Usually I get this error message

C:\Development\VBN\VAQSO\VAQSO_Setup\VAQSO_Setup.vdproj Could not find file 'C:\Development\VBN\VAQSO\VAQSO\bin\Help\Clear.ico' 'Interface not registered'

This file and path also exist. This file is in the Setup project in a directory under the Application Folder. I can make this error go away in three steps. 1-Delete the entry from the Setup project. 2-Rename the file on my hard drive. 3-Add the renamed file back into the Setup project. Usually this works on this file, but another file in the same folder will come up missing the next build.

I figure I've busted a setting someplace, but I have no idea which one. This is the only VB project I maintain so I'm on thin ice here. Any ideas why the compiler is behaving this way?

Thanks
--HamCoder

Re: Setup Project won't build/re-build

Johan Hakkesteegt22-Feb-07 22:07

Johan Hakkesteegt

22-Feb-07 22:07

Hi,

Although not the exact same problem, I have experienced similar things. You could probably investigate and experiment until you're ready to chuck your PC out of the window WTF | :WTF:

, but I recommend trying any of the following slightly more radical solutions:
1. delete the installer project, and add a new one to the solution.
2. start a new empty solution, add the main project (add existing project), and create a new installer project
3. uninstall and reinstall .NET Studio, and then solution 2.
I have spend about a week trying to solve my own problem, before I solved it in 15 minutes with solution 2.

Good luck,

Johan

My advice is free, and you may get what you paid for.

PInvoke Imbalance Stack function

sundar_mca22-Feb-07 1:39

sundar_mca

22-Feb-07 1:39

A call to PInvoke function 'Project1!Project1.Module1::NGIMAPBR_AutoDetectAndDecode2DBarcode' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

Cry | :((

Re: PInvoke Imbalance Stack function

Guffa22-Feb-07 1:54

Guffa

22-Feb-07 1:54

Have you tried what it says?

---
single minded; short sighted; long gone;

Re: PInvoke Imbalance Stack function

sundar_mca22-Feb-07 2:24

sundar_mca

22-Feb-07 2:24

Public Declare Function NGIMAPBR_AutoDetectAndDecode2DBarcode Lib "imgap32.dll" Alias "_NGIMAPBR_AutoDetectAndDecode2DBarcode@28" (ByVal hInputDIB As Long, ByVal rectSearchLocation As rect, ByVal lSearchOption As Long, ByRef lNoofBarcodes As Long, ByVal lphBarcodeInformation As Long, ByVal lphreserved1 As Long, ByVal lphreserved2 As Long) As Long

i used the above function it says thet the struct Rect must be used as the marshall attribute to be passed as argument

Re: PInvoke Imbalance Stack function

Dave Kreskowiak22-Feb-07 4:16

Export DatagridView to Excel

22-Feb-07 4:16

Apparently, you're trying to use a VB6 signature in VB.NET code. That won't work without some conversion.

For example, a Long in VB6 is a 32-bit signed integer, while in VB.NET the same Long keyword is a 64-bit signed integer. If you want to translate the code, you have to replace the VB6 Long's with VB.NET Integer's. This is the biggest reason why people get this error message when using code they don't understand.

Also, any structures must be passed as an actual structure, not a Long or Integer.

Dave Kreskowiak
Microsoft MVP - Visual Basic

Socheat.Net21-Feb-07 23:40

Socheat.Net

21-Feb-07 23:40

How can i export datagridview to excel in vb.net 2005? Please give me a example.

Thanks

................

Re: Export DatagridView to Excel

Dave Kreskowiak22-Feb-07 5:44