Can VB.NET catch exceptions without defining a local exception variable? - vb.net

In C# you can do this:
try
{
// some code here
}
catch (MyCustomException)
{
// exception code here
}
catch (Exception)
{
// catches all other exceptions
}
Notice the catch (Type) instead of catch (Type myVariable). Is this possible with VB.NET, or do you always have to declare a variable when you catch exception types, like so:
Try
...
Catch var As NullReferenceException
...
Catch var As Exception
...
End Try

Gotta be declared in vb.net.
In fact when you type in try your ide should put in the exception type and format it.
like so:
Try
Catch e As Exception
End Try

In case a search engine brings anybody else here...
C# also has a syntax where you don't have to specify the type:
try { }
catch { }
I believe that will also catch unmanaged exceptions that do not derive from System.Exception. VB.NET can do the same:
Try
Catch
End Try

Related

MVEL2 Handle a try/catch block

I need to handle a try catch block in a mvel compiled expression called from Java, something like this
try {
func1()
} catch (Exception e) {
...do something
}
func2()
From my understandings of http://mvel.documentnode.com/ it's not possible. Am I correct?
Any idea to achieve this inside the expression? Sadly I can't split the expression to handle the exception in Java or modify functions.
Thanks

How to skip particular WebElement process when locator is not found?

prinBalAgencyComm.sendKeys(testData.get("agencyCommissionPB"));
prinBalClientRem.sendKeys(Keys.TAB);
prinBalFrom2.sendKeys(testData.get("fromFB2")); //Locator not found
prinBalAgencyCommLast.sendKeys(testData.get("agencyCommissionLastPB")); //how to execute this line without fail
You can handle this by using try catch finally.
try{
//code that can result in an exception
prinBalAgencyComm.sendKeys(testData.get("agencyCommissionPB"));
prinBalClientRem.sendKeys(Keys.TAB);
prinBalFrom2.sendKeys(testData.get("fromFB2"));
}catch(Exception e)
{
//actions you want to take in case your locator isnt found or another exception occurs
System.out.println("Exception occured" + e.getMessage());
}finally
{ //the line to be executed without fail
prinBalAgencyCommLast.sendKeys(testData.get("agencyCommissionLastPB"));
}
you would have to implement a try/catch block
try {
element action
} catch (Exception e) {
//whatever you want to happen when it fails
}`
But I would ask myself why is the test not consistent with every run? Why should this step not pass every time?
One pattern you can use is:
try {}
catch {}
Place your offending code in the try block and any error code in the catch block.
If an exception is raised in the try, the catch block will be called instead of proceeding to the next line in the try

How do I catch a query exception in laravel to see if it fails?

All I'm trying to do is verify a query.
'SELECT * from table_that_does_not_exist'
Without that erroring out, I'd like to know it failed so I can return a response that states "Error: table does not exist" or the generic error.
The simplest way to catch any sql syntax or query errors is to catch an Illuminate\Database\QueryException after providing closure to your query:
try {
$results = \DB::connection("example")
->select(\DB::raw("SELECT * FROM unknown_table"))
->first();
// Closures include ->first(), ->get(), ->pluck(), etc.
} catch(\Illuminate\Database\QueryException $ex){
dd($ex->getMessage());
// Note any method of class PDOException can be called on $ex.
}
If there are any errors, the program will die(var_dump(...)) whatever it needs to.
Note: For namespacing, you need to first \ if the class is not included as a use statement.
Also for reference:
Laravel 5.5 API - Query Exception
Laravel 8.x API - Query Exception
Wrap the lines of code you wish to catch an exception on using try-catch statements
try
{
//write your codes here
}
catch(Exception $e)
{
dd($e->getMessage());
}
Do not forget to include the Exception class at the top of your controller by saying
Use Exception;
If you want to catch all types of database exceptions you can catch it on laravel Exception Handler
if ($exception instanceof \PDOException) {
# render a custom error
}
for more details about how to use laravel Exception Handler check https://laravel.com/docs/7.x/errors
Laravel 8.x
try {
$model->save(); // Use Eloquent: https://laravel.com/docs/8.x/eloquent
} catch (\Throwable $e) {
return 'My error message';
}
Note* Need to specify \Throwable $e no Throwable $e.

is there a way to handle all antlr exception types in a rule catch[...] block

I'm using ANTLR3 with the C runtime.
I'd like to do some custom error handling. What I'm really after is that if there is an antlr matching exception of any kind in a sub rule I'd like to tell ANTLR to skip trying to handle it and let it percolate up to a more global rule.
At that rule I'll log it and then try to resume.
I've set the rule catch method like so, so that all rules won't try to recover.
#rulecatch
{
if (HASEXCEPTION())
{
PREPORTERROR();
}
}
This allows me to insert catch handlers on the rules that i want.
At my rule of interest i can then use the catch syntax like so:
catch [ANTLR3_RECOGNITION_EXCEPTION]
{
PREPORTERROR();
RECOGNIZER->consumeUntil(RECOGNIZER,RCURLY);
CONSUME();
PSRSTATE->error = ANTLR3_FALSE;
PSRSTATE->failed = ANTLR3_FALSE;
}
The problem is that this syntax seems to only allow me to catch one type of exception. I'd like to be able to catch all exception types.
Is there a way to do this?
I thought I could overload all the recovery functions but then some code generates exceptions like so:
CONSTRUCTEX();
EXCEPTION->type = ANTLR3_NO_VIABLE_ALT_EXCEPTION;
EXCEPTION->message = (void *)"";
EXCEPTION->decisionNum = 23;
EXCEPTION->state = 0;
goto rulewhenEx;
which means I'll need to catch all possible exceptions.
Any thoughts??
I've ended up trying two solutions for this.
Approach 1)
Overloading the rulecatch setting to set the exception type to one specific type
#rulecatch
{
if (HASEXCEPTION())
{
// This is ugly. We set the exception type to ANTLR3_RECOGNITION_EXCEPTION so we can always
// catch them.
PREPORTERROR();
EXCEPTION->type = ANTLR3_RECOGNITION_EXCEPTION;
}
}
This allows me to use one catch block as all exceptions will be of that type.
Approach 2)
I just use multiple catch blocks and they all dispatch to a common function to handle the error
catch [ANTLR3_RECOGNITION_EXCEPTION]
{
handleException();
}
catch [ANTLR3_MISMATCHED_TOKEN_EXCEPTION]
{
handleException();
}
....

Try Catch block

I have the following code
Try
'Some code that causes exception
Catch ex as ExceptionType1
'Handle Section - 1
Catch ex as ExceptionType2
'Handle section - 2
Catch ex as ExceptionType3
'Handle section - 3
Finally
' Clean up
End Try
Suppose ExceptionType1 is thrown by the code which is handled by section - 1. After handling that in section-1, can I have control passed to section-2/section-3? Is that possible?
Change the code to catch all the exceptions in one block and determine the type and execution path from there.
You could call functions in the exception handlers.
Try
'Some code that causes exception'
Catch ex as ExceptionType1
handler_1()
handler_2()
handler_3()
Catch ex as ExceptionType2
handler_2()
handler_3()
Catch ex as ExceptionType3
handler_3()
Finally
handler_4()
End Try
You haven't specified a language, and i don't know the language, so i answer generally.
You can't do that. If you want to have common code, put that either into finally, or if it only needs to be executed for some catching cases, you can copy that code into the respective cases. If the code is bigger and you want to avoid redundancy, you can put it into a function of its own. If that would reduce the readability of your code, you can nest your try/catch blocks (at least in Java and C++. I don't know about your language). Here is an example in Java:
class ThrowingException {
public static void main(String... args) {
try {
try {
throw new RuntimeException();
} catch(RuntimeException e) {
System.out.println("Hi 1, handling RuntimeException..");
throw e;
} finally {
System.out.println("finally 1");
}
} catch(Exception e) {
System.out.println("Hi 2, handling Exception..");
} finally {
System.out.println("finally 2");
}
}
}
This will print out:
Hi 1, handling RuntimeException..
finally 1
Hi 2, handling Exception..
finally 2
put your common code into the outer catch block. Doing it using the nested version also handles cases where an exception occurs without you explicitly re-throwing the old in a catch block. It may fit to what you want even better, but it may also not.
I think you could get the behavior you want if you do nested try blocks. Once an exception is thrown, execution goes to the catch block. If nothing is rethrown, it moves on to finally.