Re: Best approach to use try catch finally - C# Discussion Boards

Best approach to use try catch finally

5-Jul-09 22:17

Searching the articles before posting may help at times. Look I found something here[^].

Pankaj Saha5-Jul-09 21:03

Pankaj Saha

5-Jul-09 21:03

Hi, I created a class library and wrote a function with the try {} catch { throw ;} finally {} manner. However I am not doing anything in the catch block, only throwing the exception. I am handling the exception the UI layer which is using that class library. I want to know the best approach to write the try block. If I use only try {} finally {} without catch block, does it good ? Confused | :confused:

Pankaj

dan!sh 5-Jul-09 21:12

5-Jul-09 21:12

Are you even allowed to skip catch? I dont think so.

If the method calling the Class library method handles the exceptions(even for the class library methods), you can avoid try-catch block in the class library method.

Pankaj Saha5-Jul-09 21:36

Pankaj Saha

5-Jul-09 21:36

I can not avoid the try catch finally in my class library. Because I am doing file operation in the class library, that's why I have to open and working on the files and in the finally block I am closing the writer/reader/file.

Pankaj

Alan N5-Jul-09 21:43

Alan N

5-Jul-09 21:43

Hi,
From the C# 2.0 standard:

There are three possible forms of try statements:
• A try block followed by one or more catch blocks.
• A try block followed by a finally block.
• A try block followed by one or more catch blocks followed by a finally block.

Alan.

Pete O'Hanlon5-Jul-09 22:06

Pete O'Hanlon

5-Jul-09 22:06

You can use try/finally without the catch, but you have to think about why you are doing this. As you're not catching exceptions at the level that they are being thrown, you are storing up a lot of work for the higher levels. By this, I mean that you could catch the exception and do something meaningful with it, rather than relying on the UI reporting that there was an error.

For instance, we have a library that catches an error where the SqlConnection has become unavailable, and (in the appropriate catch), reconnects the SqlConnection before it attempts to process the SQL again.

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

My blog | My articles | MoXAML PowerToys | Onyx

Pankaj Saha5-Jul-09 22:38

Pankaj Saha

5-Jul-09 22:38

I do not want to use the try catch finally in the class library, however I am doing file operations in the class library. I open/read/write the file with the stream reader/writer object and have to close that reader/writer in the finally block. If any error occurs during the read/write operation then reader must be close, that's why I have to use the finally block to close the reader. Here is the code

public string ReadXmlNodeValue(string fileName, string xmlPath)
{
string retValue = "";

StreamReader sr = null;

XmlDocument doc = new XmlDocument();

try
{
sr = new StreamReader(fileName, Encoding.UTF8);

doc.Load(sr);

XmlNode element = doc.SelectSingleNode(xmlPath);

retValue = element.InnerText;

}
catch
{
throw;
}
finally
{
sr.Close();
sr = null;
doc = null;
}

return retValue;
}

Can I write the above code without try catch finally block and it will close the reader if any error is generated during the process ?

Pankaj

Pete O'Hanlon5-Jul-09 23:19

Pete O'Hanlon

5-Jul-09 23:19

Pankaj Saha wrote:
Can I write the above code without try catch finally block and it will close the reader if any error is generated during the process ?

If you mean, can you dispense with try/finally as well, then you should not. The finally portion will close the reader, regardless as to whether or not an exception is thrown. As StreamReader is a disposable object though, you could always rewrite this with:

using(StreamReader sr = new StreamReader(fileName, Encoding.UTF8))
{
  // Do the file stuff.
}

When StreamReader is disposed the stream is closed (if it is open).

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

My blog | My articles | MoXAML PowerToys | Onyx

Luc Pattyn6-Jul-09 0:23

Luc Pattyn

6-Jul-09 0:23

Hi,

a try block accepts one or more catch blocks and one or no finally blocks;
When there is a finally block, the catch blocks can be left out.

A catch block that only throws does not make any sense; just throw it out!

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

The quality and detail of your question reflects on the effectiveness of the help you are likely to get.
Show formatted code inside PRE tags, and give clear symptoms when describing a problem.

PIEBALDconsult6-Jul-09 4:31

PIEBALDconsult

6-Jul-09 4:31

Exactly.

Error after selecting text in richtextbox

Luc Pattyn6-Jul-09 5:23

Luc Pattyn

6-Jul-09 5:23

Luc Pattyn [Forum Guidelines] [My Articles]

The quality and detail of your question reflects on the effectiveness of the help you are likely to get.
Show formatted code inside PRE tags, and give clear symptoms when describing a problem.

Khawar Abbas15-Jul-09 20:50

Khawar Abbas1

5-Jul-09 20:50

I am developing an application in C# and using richtextbox. After formatting the text when i select all the text it gives exception given below:

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
at RichTextEditor.Editor.ucEditor.rtbDoc_SelectionChanged(Object sender, EventArgs e) in E:\MDCENTERWINAPP\Editor\ucEditor.cs:line 841
at System.Windows.Forms.RichTextBox.OnSelectionChanged(EventArgs e)
at System.Windows.Forms.RichTextBox.WmSelectionChange(SELCHANGE selChange)
at System.Windows.Forms.RichTextBox.WmReflectNotify(Message& m)
at System.Windows.Forms.RichTextBox.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Any Suggestion...............

Do good and have good.

Re: Error after selecting text in richtextbox

Alan N5-Jul-09 21:49

Alan N

5-Jul-09 21:49

Hi,
The message gives the location of the exception causing statement in the source code.

Silent Eagle wrote:
System.NullReferenceException: Object reference not set to an instance of an object.
at RichTextEditor.Editor.ucEditor.rtbDoc_SelectionChanged(Object sender, EventArgs e) in E:\MDCENTERWINAPP\Editor\ucEditor.cs:line 841

If the error on line 841 is not obvious, set a breakpoint there and investigate further with the debugger.

Alan.

Re: Error after selecting text in richtextbox

Luc Pattyn6-Jul-09 0:26

Luc Pattyn

6-Jul-09 0:26

Hi
as Alan said, look at line 841.

Read the Exception text, it is there to help you. Look in particular to the first line that mentions one of your filenames, and a line number.
And tell Visual Studio to always show line numbers in edit windows (menu Tools/Options/TextEditor/AllLanguages...).

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

The quality and detail of your question reflects on the effectiveness of the help you are likely to get.
Show formatted code inside PRE tags, and give clear symptoms when describing a problem.

Report Viewer Control -

devvvy5-Jul-09 20:25

devvvy

5-Jul-09 20:25

hello

In ASP.NET, we can use Report View control to access reports on a Reporting Service instance.

Now,
(1) if I want default PDF format - i.e. without having use to click that "Export to PDF" button in reporting viewer command bar...?
(2) What if some of my own .NET process (MyReportServer.exe) wants to call SQL/Reporting Service directly to export PDF? How do I do that?

Thanks

dev

how to get only time from datetime?

swetha_insoft5-Jul-09 20:22

swetha_insoft

5-Jul-09 20:22

how to get only time from this string
string strtime="Tue-07-Jul-2009 12:00 PM";

SeMartens5-Jul-09 20:26

SeMartens

5-Jul-09 20:26

Well try to parse the string with DateTime.Parse() and then access DateTime.Hour and DateTime.Minutes. Have a look at http://msdn.microsoft.com/en-us/library/system.datetime.aspx[^]

It's not a bug, it's a feature!

Check out my CodeProject article Permission-by-aspect.

Me in Softwareland.

Anubhava Dimri5-Jul-09 20:41

Anubhava Dimri

5-Jul-09 20:41

Set the format of time in which you want to get it.
strtime.format("dd/MM/yyyy");

If you can think then I Can.

himanshu25615-Jul-09 20:44

himanshu2561

5-Jul-09 20:44

Try like
(1)

string strtime = "Tue-07-Jul-2009 12:00 PM";
      strtime = strtime.Substring(strtime.IndexOf(" ")+1,strtime.Length-strtime.IndexOf(" ")-1);

(2)

DateTime dt3=DateTime.Parse(strtime);
        strtime= dt3.ToShortTimeString();

himanshu

how to write in excel cells using DataReader if a particular cell is “ReadOnly” using C#

stancrm5-Jul-09 20:56

stancrm

5-Jul-09 20:56

string strtime = "Tue-07-Jul-2009 12:00 PM";
string format = "ddd-dd-MMM-yyyy hh:mm tt";
CultureInfo formatProvider = new CultureInfo("en-US");
DateTime dt = DateTime.ParseExact(strtime, format, formatProvider);

Console.WriteLine(dt.ToString("hh:mm:ss tt"));

Krishna Aditya5-Jul-09 20:20

Krishna Aditya

5-Jul-09 20:20

Hi Guys,

I tried a lot to figure out how to skip writin onto a particular excel cell using C#, but couldnt get the proper logic.

my eg:
*Team Leader (required)     abcxyz     User1     user2
Customer Interface Focal     dfgidf     user23     user3*

each of the names above has to be in a particular cell... but in the excel template, first cell (Team Leader (required)) is readonly, so i cant write into that cell, so my final excel sheet should show

                                          abcxyz     User1     user2
Customer Interface Focal     dfgidf     user23     user3.....
.....

i tried various logics for this... please see the code below

1. Microsoft.Office.Interop.Excel.Workbook   SelWorkBook = excelappln1.Workbooks.Open(curfile,
      0, false, 5, "", "", false, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "", true, false, 0, false, false, false);

      Microsoft.Office.Interop.Excel.Sheets      excelSheets =      SelWorkBook.Worksheets;

      Microsoft.Office.Interop.Excel.Worksheet      excelworksheet =      (Microsoft.Office.Interop.Excel.Worksheet)excelSheets.get_Item(CurSheetName);

      Microsoft.Office.Interop.Excel.Range      excelRange =      excelworksheet.UsedRange;

if ((!excelworksheet.Cells[CurTaskNode.DATA_MIN_ROW + minRow, CurTaskNode.DATA_MIN_COL + minCol]).Locked)
   {

            // Assigning the Value from reader to the particular cell in excel sheet excelworksheet.Cells[CurTaskNode.DATA_MIN_ROW + minRow, CurTaskNode.DATA_MIN_COL +         minCol] = values[iValueIndex];
            iValueIndex++;
   }

but the error shows, in the if statement
Error     1     Operator '!' cannot be applied to operand of type 'object'

so, please say how to handle this case.

Thanks
Ramm

Re: how to write in excel cells using DataReader if a particular cell is “ReadOnly” using C#

dan!sh 5-Jul-09 20:51

Re: how to write in excel cells using DataReader if a particular cell is “ReadOnly” using C#

5-Jul-09 20:51

Krishna Aditya wrote:
if ((!excelworksheet.Cells[CurTaskNode.DATA_MIN_ROW + minRow, CurTaskNode.DATA_MIN_COL + minCol]).Locked)

Can you see some incorrect braces here?

Moreover, I cannot see any locked property for cells. However, you can use Microsoft.Office.Interop.Excel.Range.Locked for this.

Krishna Aditya5-Jul-09 20:57

Krishna Aditya

5-Jul-09 20:57

ya d@nish,

I used the same Microsoft.Office.Interop.Excel.Range.Locked for test...

if ((!Microsoft.Office.Interop.Excel.Range (excelworksheet.Cells[CurTaskNode.DATA_MIN_ROW + minRow, CurTaskNode.DATA_MIN_COL + minCol])).Locked)

{
/// stuff her
}

it shows error here
Error 1 'Microsoft.Office.Interop.Excel.Range' is a 'type', which is not valid in the given context

Am I using the property wrongly here??

Please help.

Thanks
Ramm

Re: how to write in excel cells using DataReader if a particular cell is “ReadOnly” using C#

dan!sh 5-Jul-09 21:10