Re: Advice about Open Database Connection - C# Discussion Boards

Nagy Vilmos13-Mar-09 4:59

Nagy Vilmos

13-Mar-09 4:59

Nice answer today:

- create one session and use it for all your updates.
- use transations to ensure atomic units.

Panic, Chaos, Destruction.
My work here is done.

soulidentities13-Mar-09 5:06

soulidentities

13-Mar-09 5:06

I forget to mention that im using for Windows application.
Does windows application support session?

Can you tell me a lil detail
Thanks

Nagy Vilmos13-Mar-09 5:12

Nagy Vilmos

13-Mar-09 5:12

Can you tell me how to use google?

Panic, Chaos, Destruction.
My work here is done.

soulidentities13-Mar-09 5:17

soulidentities

13-Mar-09 5:17

im sorry but i didnt expect anything ques like that.
I understand what u mean...
Np thanks

Yes i can tell you...google it

Dave Kreskowiak13-Mar-09 5:31

Dave Kreskowiak

13-Mar-09 5:31

It's bad practice to open a connection to the database and leave it sit idle. SQL Server connection licenses are quit expensive.

Normally, you'd get all of your data from the forms, open the connection, start a transaction, do all of your queries to update the database, commit the trasaction, and close the connection.

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Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007, 2008

Nagy Vilmos13-Mar-09 10:30

Nagy Vilmos

13-Mar-09 10:30

Not sure I agree there. There is normally an expense to continuously opening and closing connections. In most systems there is no need for a connection per user, but often it is beter to maintain a pool of sesions and when a client needs to access the database it will take the next available session.
Unless of course we're talking about single user, single connection, single cell. Then the connect and drop might be excusable, but generally keep sessions open for the life of the system, but not always one per client.

Panic, Chaos, Destruction.
My work here is done.

Dave Kreskowiak13-Mar-09 12:23

Dave Kreskowiak

13-Mar-09 12:23

Well, there's a different perspective. ADO.NET caches connection client-side. You can open and close them all you want without suffering a huge performance hit by going back to the SQL Server to establish the connection. In you're code's eyes, the connection is closed, but ADO.NET maintains the open connection with the server, keeping it cached in a connection pool. When you code opens the connection again, it's already open by ADO.NET and it just executes the query.

Where I work, there are SQL Servers with only 1,000 seats, but supporting about 2,000 users because the application's data use is pretty sparse, even though the apps are open all day long...

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007, 2008

Luc Pattyn13-Mar-09 6:28

Luc Pattyn

13-Mar-09 6:28

williamnw wrote:
Can you tell me how to use google?

That is easy.
Take the content of your subject line, and paste it into google's editbox
without all the "hi", "doubt", "urgent" and "plz" of course (hoping that leaves something to search for)

Smile | :)

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- before you ask a question here, search CodeProject, then Google
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get
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Read lines on exel file

abbd13-Mar-09 4:05

Re: Read lines on exel file

13-Mar-09 4:05

Hello,

I would read all lines of my excel file, can you help me? thank you verry mutch.

Eddy Vluggen13-Mar-09 4:19

Exception de HRESULT : 0x800401A8

13-Mar-09 4:19

Read the previous post, that's about writing Excel. Reading is done in roughly the same way.

You can Google for examples if you like Smile | :)

I are troll Smile | :)

abbd13-Mar-09 4:50

13-Mar-09 4:50

Hello ,

I try for :

<br />
Microsoft.Office.Interop.Excel.Application excelApplication = null;<br />
            Microsoft.Office.Interop.Excel.Workbook workbook = null;<br />
            Microsoft.Office.Interop.Excel.Worksheet worksheet = null;<br />
<br />
            excelApplication = new Microsoft.Office.Interop.Excel.Application();<br />
            excelApplication.Visible = false;<br />
<br />
            workbook = excelApplication.Workbooks.Open(@"D:\Après\mailing_RA_20090219.xls", 0, false, 5, "", "", false, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "", true, false, 0, true, false, false);<br />
            worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Worksheets[2];<br />
<br />
<br />
<br />
<br />
            excelApplication.Quit();<br />
            excelApplication = null;<br />
<br />
            string cellValue = "";<br />
            object cellObject = null;<br />
            Microsoft.Office.Interop.Excel.Range range = null;<br />
<br />
<br />
            range = (Microsoft.Office.Interop.Excel.Range)worksheet.Cells[3,2];<br />
<br />
            cellObject = range.get_Value(null);<br />
            cellValue = (cellObject == null ? "" : cellObject.ToString().Trim());<br />
<br />
<br />
            Console.WriteLine(cellValue);<br />

i have the exception on : range = (Microsoft.Office.Interop.Excel.Range)worksheet.Cells[3,2];, thank you verry mutch.

Eddy Vluggen13-Mar-09 5:03

13-Mar-09 5:03

Is there a chart in that range of cells?

I are troll Smile | :)

abbd13-Mar-09 5:07

13-Mar-09 5:07

Yes, I have 1506 rows and 10 collumns, thank you verry mutch.

Eddy Vluggen13-Mar-09 5:28

13-Mar-09 5:28

If there's a graphic or a chart at cell 3,2 then you won't be able to convert this to a string. That's seems to be the main problem when you Google for the error-code.

Furthermore, you're closing the Excel-application before you're reading, on these lines;

excelApplication.Quit();
excelApplication = null;

Is that as it was intended?

I are troll Smile | :)

abbd13-Mar-09 5:57

13-Mar-09 5:57

Thank you,

i try :

<br />
Microsoft.Office.Interop.Excel.Application excelApplication = null;<br />
            Microsoft.Office.Interop.Excel.Workbook workbook = null;<br />
            Microsoft.Office.Interop.Excel.Worksheet worksheet = null;<br />
<br />
            excelApplication = new Microsoft.Office.Interop.Excel.Application();<br />
            excelApplication.Visible = false;<br />
            try<br />
            {<br />
                workbook = excelApplication.Workbooks.Open(@"D:\Après\mailing_RA_20090219.xls", 0, false, 5, "", "", false, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "", true, false, 0, true, false, false);<br />
                worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Worksheets[2];<br />
<br />
<br />
<br />
<br />
                <br />
<br />
                string cellValue = "";<br />
                object cellObject = null;<br />
                Microsoft.Office.Interop.Excel.Range range = null;<br />
<br />
<br />
                range = (Microsoft.Office.Interop.Excel.Range)worksheet.Cells[4,7];<br />
<br />
                cellObject = range.get_Value(null);<br />
                cellValue = (cellObject == null ? "" : cellObject.ToString().Trim());<br />
<br />
                Console.WriteLine(cellValue);<br />
<br />
                excelApplication.Quit();<br />
                excelApplication = null;<br />
<br />
                Console.Read();<br />
<br />
               <br />
                <br />
<br />
            }<br />
            catch (Exception ex)<br />
            {<br />
                Console.WriteLine(ex.ToString());<br />
                Console.Read();<br />
            }<br />

But i have an empty output, thank you verry mutch.

Luc Pattyn13-Mar-09 6:30

Luc Pattyn

13-Mar-09 6:30

Sounds like two monologues intertwined...

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

abbd13-Mar-09 6:54

13-Mar-09 6:54

I don't find any thing.please help me thank you verry mutch.

Eddy Vluggen13-Mar-09 8:40

13-Mar-09 8:40

I'm sorry, but I got no clue how Frown | :(

I are troll Smile | :)

How to create a excel file by C# in Window application

v_130-Sep-11 21:05

v_1

30-Sep-11 21:05

/*excelApplication.Quit();
excelApplication = null;

string cellValue = "";
object cellObject = null;
Microsoft.Office.Interop.Excel.Range range = null;*/

remove this code Bro Smile | :)

ArunUtkarshaRana13-Mar-09 3:38

ArunUtkarshaRana

13-Mar-09 3:38

I am trying to convert xml data to Excel. But, I am not able to figure out how to create a excel by C#. Pls help me.

Re: How to create a excel file by C# in Window application

Xmen Real 13-Mar-09 3:44

Xmen Real

13-Mar-09 3:44

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Re: How to create a excel file by C# in Window application

ArunUtkarshaRana13-Mar-09 3:55

ArunUtkarshaRana

13-Mar-09 3:55

Not sure what it is.

Re: How to create a excel file by C# in Window application

Eddy Vluggen13-Mar-09 4:01