I like VB.Net, but there is something that is driving me nuts. Too many times when an exception occurs, it simply continues somewhere else, usually by exiting the sub or function, but otherwise keeps on rolling. As an example, I was using Asc() instead of AscW(). It didn't throw an exception, it just left the function as if a Return was executed. Meanwhile I'm leaving red dot stop points all over like it has chicken pox trying to figure out what is causing it.
Is there a setting that can be used to used to actually cause VB to stop and give a line number?
Try catch statements will help you out greatly.
Take a read here: https://msdn.microsoft.com/en-us/library/fk6t46tz.aspx
Have you tried using a Try..Catch..Finally statement. E.g. The ex.string will put the exception into a string in the message and tell you the vb line.
Try
'code here
Catch ex as Exception
MessageBox.Show("Something went wrong. " & ex.ToString, "Data Error ")
End Try
Related
I have been experiencing a problem with one of my vb applications where it is crashing at a certain time of day. In my code, there are only 4 places where that could be the cause of the crash. Three of them are from SQLDataSource queries and the other is in the code behind. I am pretty sure that I don't have a problem with the code behind as I have a using block in place. Further more, inside of that block I have a try catch finally where in the finally I am Disposing the command as well as the connection and Closing the connection. I have been reading some articles that tell me that I should use a SqlDataSource "selected" event to close the connection. I gave that a try but didn't have any success. This is the error that I am receiving:
SqlException (0x80131904): Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
This makes me feel like the "selected" event is not having a chance to get fired. So I thought I should try the "selecting" event. In it, I am trying to grab the connection string and close it. But I am not quite sure I am going down the correct path because I have been unable to catch exceptions inside of that event. Can someone out there please give me a hand with this issue I am facing?
Edit:
This is an example of how I am trying to use the selected event to close the connection
If Not IsNothing(e.Exception) Then
Debug.Print("Exeception encounted while selecting for sqlData")
End If
e.ExceptionHandled = True
And here is and example of how I am trying to use the selecting event (I cannot figure out if an exception has been thrown here).
Dim sqlDataConn As SqlConnection = New SqlConnection("MYConnectionString")
sqlDataConn.Dispose()
If you want to intercept SqlException you need to use explicit "using", i.e. try/catch. Then, you can determine specific issue by the Number property.
try
catch ex as SqlException
MessageBox.Show(ex.Number)
if ex.Number = xxx then
' do something
end if
catch ex as Exception
finally
end try
if the question about handling this
If Not IsNothing(e.Exception) Then
Debug.Print("Exeception encounted while selecting for sqlData")
End If
you can check the exception type
If e.Exception IsNot Nothing AndAlso TypeOf e.Exception Is SqlException Then
.....
It would help if you did a breakpoint and found the query that was having this issue. The timeout issue is when a long-running query kills itself because it ran past the default timeout period.
A quick and dirty solution could be to just use a larger timeout in the connection strings you use, but long running queries can usually be a bad sign of an unoptimized query and should be addressed before your database grows any larger.
Wondering if the following can be done in a simple way:
Try
Some Statements
Catch ex As ...
Error handling stuff
NotCatch
Code to handle *only* if there was no Catch
End Try
A Finally bloc will not do it, because it is executed even if the Catch was executed. Putting the code after the End Try doesn't work either, as it's always executed. I tried to place an Exit Try after the Error handling stuff, but then nothing is executed any more before the End Try.
Is there an clean and easy way to do this without variables to remember that the Catch was executed?
The normal way is like this:
Try
Some Statements
Code to handle *only* if there was no Catch
Catch ex As ...
Error handling stuff
End Try
This works because as soon as an exception is thrown, control jumps to the catch block and the rest of the try block is ignored. Or to put it another way: If a line in the "try" runs, then you know there hasn't been an exception yet.
If you have other requirements that means this wont work then you'll need to provide more information.
I'm working through a Hair Salon application in VB.NET. Basically the user is able to select the stylist, service(s), age category and enter the number of visits. I then have a Calculate button in order to calculate the total price. I'm required to use Try-Catch for exception handling but I'm not too familiar with it. I'm assuming it's used for error handling, in which case how would I check to see if client visits is greater than 0 and to check to see if the value entered is an integer? Here is what I've tried with the client visits:
Try
(intClientVists > 0)
Exit Try
Catch ex As Exception When
(intClientVists < 0)
Exit Try
End Try
Just hoping someone can steer me in the right direction because I'm not really sure what I'm doing for this particular aspect of the application. Thanks.
Yes, Try/Catch blocks are used for error handling. However, they're not really for this kind of error. Try/Catch blocks are more for errors made by the programmer or the computer (could not allocate memory, could not connect to database, could not open a file, tried to divide by zero, could not cast a value to the specified type) than for errors made by the user (entered a wrong number).
Instead, you want a simple If/Else block:
If intClientVists > 0 Then
'Do something
Else
'Do something else
End If
If you really want to use exception handling for this (again: not normally the best choice), here is how it might look:
Try
If intClientVists < 0 Then Throw New InvalidOperationException()
'Data is OK. Continue processing here
Catch Ex As InvalidOperationException When intClientVisits = 0
'Show one error message
Catch Ex As InvalidOperationException When intClientVisits < 0
'Show different error message
End Try
This MSDN article gives you a list of .NET exceptions that you can use in a Try-Catch. These are actual errors as opposed to input validation checking, like Joel explained.
Basically, you put some logic in the Try block, and if you want to do something in the case of a specific exception, then you catch that exception type and put your logic in that Catch block. Then as a "catch-all" just simply catch "Exception" to do something no matter what type the exception is.
In your particular case, it sounds like the most likely use of a Try-Catch would be if the user inputs the number of visits into a regular text box in which they could enter letters. Here is an example of what you could do for that:
Try
If CInt(txtNumVisits.Text) > 0 Then
'logic here
End If
Catch ex As Exception
'If user entered something other than an integer in that box then an InvalidCastException will be caught
'enter logic here for if that's the case. For example:
MessageBox.Show(Me, "Please enter a number >= 0", "Invalid Input")
txtNumVisits.Focus()
End Try
So in my vb.net application, i've got alot of try and catch blocks for error handling, especially whenever my app talks to the db.
i'm running through a series of if/elseif statements to see if
ex.tostring.contains("Unable to connect to any of the specified MySQL hosts")
and various bits like that.
At the minute, I wrote this out and copy and pasted it into each catch, but I know there will be a much more efficient way to do this whereby the code is just in one place and called as and when required.
I tried to implement it as a function, but I had trouble passing info to the function.
So i thought I'd ask and see how you guys go about doing this?
You don't need multipe try...catch statements for a program. One is enough.
If i understood you correctly, you want to print or show the error that occured inside the Try block.
Public Sub main()
Try
'Do something
Catch ex As Exception
End Try
Try
'Do something else
Catch ex As Exception
End Try
If ex.tostring.contains("something") than
End Sub
Instead you can do something like this:
Public Sub main()
Try
'Do all your code here.
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
In this part, the compiler will automaticlly print the error occured in the program.
You can perform some action based on the type of exception thrown. Checking the text if not recommended as this could change with a new version of .net or mysqldata
Try something like this:
Try
'
' Programming lines of code
'
Catch exError As MySqlException
' an error occurred with MySql
Catch e As Exception
' a General error occurred
Finally
' Cleanup custom and unmanaged resources if necessary
End Try
Have a look at the MySQL Documentation for their recommendations
I want the designer to catch the error when I am debugging and I want the user to see my friendly message if an error occurs for them. I know I can acomplish this with the following:
#If Debug=False Then
Try
#End If
'some code here
#If Debug=False Then
Catch ex as exception
Messagebox.Show("Errors suck")
End Try
#End If
I do not want to have to write all the #statements and having them cluttering up my code. It seems like this should be a common need and there has to be a better way. Does anyone know a better way?
In VS.NET you can say whether you want the debugger to break when an exception is thrown (not just when it's unhandled).
Look on the Debug | Exceptions... menu item (Ctl-Alt-E on my keyboard shortcuts). Pick the excepption you're interested in, then tick the "thrown" box for that exception.
You can tick that box at several levels (all CLR exceptions, all CLR exceptions in a given namespace, or very specific exceptions)
There is no good way to get it to ignore a try catch other than what you've done. But you can make the code a little bit cleaner and essentially get the same effect. You essentially are trying to prevent the action in the catch block from running. A better way to do that is a conditionally compiled method.
Try
...
Catch ex As Exception
DebugLog(ex)
Throw
End Try
<Condition("DEBUG)> _
Public Sub DebugLog(ByVal ex As Exception)
Messagebox.Show("errors suck")
End Sub
In the catch section of your Try..Catch you should write the exception message, stacktrace, and anything else you may want to a log file -- additionally you could write that data to the Windows Event log as well.
At worst, you could just put break-points in the Catch section of your Try..Catch blocks, since you shouldn't normally hit them it should'nt be a big deal once setup.
Here is how I do it:
Enabled:
Try ' : Catch: End Try
doSomething
andSomeMore
etcEtc
' Try
Catch ex As Exception
handleException
End Try
Disable the above by deleting the two comment characters:
Try : Catch : End Try
doSomething
andSomeMore
etcEtc
Try
Catch ex As Exception
handleException
End Try