Visual Basic

Re: Database -- What am i not understanding.

17-Dec-04 12:21

I have an ms access db with many 'views' (queries) within the database that I want to use with ADO.NET but it seems I'm having to reinvent the wheel to use them the way i want.

Simplified example:

Lets say i have a query within Access

"Select FirstName, LastName, FirstName + ' ' + LastName as FullName FROM Customers"

Now I use that in a DataTable bound to a DataGrid -- When i enter (or edit) the FirstName and LastName and move to the next row it doesn't update the 'calculated field' FullName.

I know I can make a 'Calculated Column' and make it work but im trying not to have to write so much dang code and use what already works. Am I just missing somthing obvious? Is there a way to tell ADO that the field should calculate 'LIVE' using the sql, or do I have to insert into code every calculation done with the data as a calculated column?

Dave Kreskowiak17-Dec-04 14:14

Re: Database -- What am i not understanding.

17-Dec-04 14:14

OICU812 wrote:
When i enter (or edit) the FirstName and LastName and move to the next row it doesn't update the 'calculated field' FullName.

That's because it's not a calculated column. It's a 3rd column, called FullName, in a table returned by the Jet Engine, which did the "calculation." In order to see the changes with the code you've written, you'll have to write the FirstName and LastName fields back to the database and then refresh the dataset, thereby returning a new FullName column.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

OICU81217-Dec-04 18:57

custom sorting datatables

17-Dec-04 18:57

Thanks for replying. Thats what I thought I would have to do. I just wanted to be sure there wasn't something more efficent that did that automatically.

Bitmaps and GDI+

Michael Parkin17-Dec-04 10:10

Michael Parkin

17-Dec-04 10:10

I have written a routine to manipulate a large bitmap (actually it is a raster image of a map).
After loading the bitmap into memory I have used DrawImage() to zoom in and out and scroll the map in a picturebox.
However, the quality of the same bitmap in the picturebox is OK, but no where nere as good as the image displayed in the windows Picture and Fax viewer. Can anyone explain why? Does the windows viewer use GDI+ or perhaps DirectX. Is there a way of tweaking drawimage to get better results.

thanks in anticipation.

regards,

MP

mfriedenthal17-Dec-04 8:07

mfriedenthal

17-Dec-04 8:07

Please note that I am a beginner VB.net programmer. Any help you can offer would be appreciated.

I am trying to sort a datatable loaded from an SQL db table. There are 2 sort keys, both ascending, and 9 other columns. The primary key, "PurchaseOrderID", can contain nulls, although it is usually a string of format "999999_999". After loading the ds, I use the following code to try to sort the records:

Dim myDataView As DataView
myDataView = ds.Tables("tPIA").DefaultView
myDataView.Sort = ("PurchaseOrderID, TimeNeeded")

The problem is I need the rows with null values in PurchaseOrderID to all sort to the high end. I know one can write a custom comparer to modify sort order but I haven't seen the syntax of how one can use a comparer with a dataview.

Can this be done? If so, what's the syntax?

If not, do you have any other suggestions? I originally loaded the SQL table into a Collection but there didn't seem to be a sort method available there. So I loaded the Collection into an array and wrote a custom comparer, but then I couldn't seem to sort on the 2 fields, as required.

Thank you,
mif

mif

OICU81217-Dec-04 11:23

17-Dec-04 11:23

Try this

MyDataView.Sort = "PurchaseOrderID, TimeNeeded ASC"

-or-

MyDataView.Sort = "PurchaseOrderID ASC, TimeNeeded ASC"

Use DESC for Descending

*EDIT*

I just tried it with a dataview containing null values and it sorts the null values to the top of list in my datagrid. I really don't see a problem with your code. I thought maybe the parentheses in your .sort code was the problem but it works either way.

LadyReader20-Dec-04 4:41

LadyReader

20-Dec-04 4:41

Thank you for the help - however I am not getting the results expected. Although ASC is the deafult, I did add ASC to both sort keys:
myDataView.Sort = ("PurchaseOrderID ASC, TimeNeeded ASC")

Here is a sample of the output, where PurchaseOrderID is column(2) and TimeNeeded is column(9) on a 0 to 11 basis:

Row: 119
34028_1_1, 7/25/2005 12:00:00 AM, {unspecified}, , 12345-0003, 1, xxx, 0, , 7/25/2005 12:00:00 AM, M,
------------------------
Row: 120
33734_1_1, 9/11/2005 12:00:00 AM, {unspecified}, , 12346-0002, 1, xxx, 0, , 9/11/2005 12:00:00 AM, M,
------------------------
Row: 121
33597_1_1, 12/12/2012 12:00:00 AM, {unspecified}, , 12345-0001, 1, xxx, 0, , 12/12/2012 12:00:00 AM, M,
------------------------
Row: 122
33596_1_1, 12/12/2012 12:00:00 AM, {unspecified}, , 12345-0001, 1, xxx, 0, , 12/12/2012 12:00:00 AM, M,
------------------------
Row: 123
33596_1_2, 12/12/2012 12:00:00 AM, {unspecified}, , 12345-0001, 2, xxx, 0, , 12/12/2012 12:00:00 AM, M,
------------------------
Row: 124
33597_1_2, 12/12/2012 12:00:00 AM, {unspecified}, , 12344-0001, 2, xxx, 0, , 12/12/2012 12:00:00 AM, M,
------------------------
Row: 125
32798_1_1, 12/31/2029 12:00:00 AM, {unspecified}, , 1234-0003, 2, xxx, 0, , 12/31/2029 12:00:00 AM, M,
------------------------
Row: 126
32412_1_5, 12/31/2029 12:00:00 AM, {unspecified}, , 12345-0002, 3, xxx, 0, , 12/31/2029 12:00:00 AM, M,
------------------------
Row: 127
118121-000, 1/28/2005 12:00:00 AM, {unspecified}, 25, 12345-005, 9, xxx, 0, , 1/28/2005 12:00:00 AM, M,
------------------------
Row: 128
117604-101, 1/13/2005 12:00:00 AM, 147347_020, 540, 12345-1234-006, 1, {unspecified}, 0, 12/22/04, 1/18/2005 12:00:00 AM, P,
------------------------
Row: 129
117749-101, 2/3/2005 12:00:00 AM, 147347_021, 540, 12345-1234-006, 1, {unspecified}, 0, 12/22/04, 2/8/2005 12:00:00 AM, P,
------------------------
Row: 130
117941-101, 3/9/2005 12:00:00 AM, 150236_005, 105, 12345-001, 10500, {unspecified}, 0, 03/07/05, 1/19/2005 12:00:00 AM, M,
------------------------
Row: 131
118122-000, 1/26/2005 12:00:00 AM, {unspecified}, 20, 12345-004, 12, xxxx, 0, , 1/26/2005 12:00:00 AM, M,
------------------------
Row: 132
118110-000, 12/20/2004 12:00:00 AM, {unspecified}, 20, 12345-003, 5, xxxx, 0, , 12/9/2004 12:00:00 AM, M,
------------------------

Take a look at rows 126 and 127 - although PurchaseOrderID has been {unspecified} through this point, TimeNeeded has jumped backwards from 12/31/2029 to 1/28/2005. The watch has these colums delimited by "#"s so I have reason to believe that .net is indeed seeing the fields as dates and not strings.
Can you offer any other suggestions?
Thanks!
m

OICU81221-Dec-04 21:13

21-Dec-04 21:13

mfriedenthal wrote:
The watch has these colums delimited by "#"s so I have reason to believe that .net is indeed seeing the fields as dates and not strings.

Are you sure the data isn't being handled as a string? I made a quick table in ms access and it sorted it fine with the "TimeNeeded" column as a DATE/TIME but when i changed it to a string it basically returned results like you show. Double check the column data type:

Debug.WriteLine(MyDataSet.Tables("MyTable").Columns("TimeNeeded").DataType.ToString)

Do the same for your PurchaseOrderID column. Other than being the wrong datatype I can't understand why it doesn't work for you.

Check the file os open or not in vb

LadyReader22-Dec-04 4:16

LadyReader

22-Dec-04 4:16

Thanks for the advice, but I did as you suggested and I got back:

System.DateTime
System.String

for TimeNeeded and PurchaseOrderID, respectively. Which is what I expected.

Still researching...
Any help would be appreciated.

Thanks!

Member 158672017-Dec-04 3:18

Member 1586720

17-Dec-04 3:18

I want to check wether the file is being used by some other application or software i want to do some task if that file is being used by some other application.

for ex. if a slideshow player is opening some jpg files and playing slide show
there is a file names kkk.jpg in sequence of the slideshow i want to check weather the file is accessed or not i will check before the slideshow begins

We are presenting a slideshow of our teachers at one photograph we want to play a specified music i want to use vb for this..

I will be thankful if any body helps me.....

Re: Check the file os open or not in vb

Dave Kreskowiak17-Dec-04 6:13

17-Dec-04 6:13

Uhhh, why? PowerPoint can already play the music when a specific slide is shown. All you have to do is tell it which file to play...

Without writing a specific file system extension, you can't reliably monitor the file to see if it was opened by some other process. In order to get this to PARTIALLY work, you would have to constantly try and open the file exclusively, denying any shared access, just to see if the file was opened by some other process. If the file opens, no other process has it open. If it doesn't open, something else has it open. But, there are multiple problems with doing this:

1) You must try to open file, repeatedly, fast enough so that you don't miss the file being opened, read, and closed, in between your attempts to open the file. This will have the effect of degrading system performance and slowing down all other applications.

2) As explained in 1, you could easily miss a file being open, then closed.

3) If your monitor manages to open the file, you will automatically prevent any other app from opening that file. This will cause your presentation to stop or possibly crash altogether.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Making Monitor Black

Member 158672017-Dec-04 2:50

Member 1586720

17-Dec-04 2:50

How to make Display Blank Screen for a Specified Period in VB is there any function.

Dave Kreskowiak17-Dec-04 6:00

17-Dec-04 6:00

Why would you want to do this, considering your app has to play nice with others on a SHARED system?

If I was using your app and it blanked the entire screen, preventing me from using my other apps, I'd click close on your app then, promptly, uninstall it...

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Member 158672017-Dec-04 14:23

Member 1586720

17-Dec-04 14:23

i want to do some background process which should not display

kindly help me

OICU81217-Dec-04 19:29

17-Dec-04 19:29

Ramesh Yadavalli wrote:
i want to do some background process which should not display

There are all kind of thing you can do with a background process without anyone seeing it. But making the whole screen black sound like you're trying to make a prank or get fired from your job!

But it's really easy

<br />
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load<br />
        Me.BackColor = Color.Black<br />
        Me.FormBorderStyle = FormBorderStyle.None<br />
        Me.WindowState = FormWindowState.Maximized<br />
    End Sub<br />

Dave Kreskowiak18-Dec-04 4:37