CODEWITHSUNDEEP
vb.netfunctionerror-handling
genespos
genespos

Reputation: 3311

VB.net logic to catch errors in functions

I'm not a pro and I learn by myself a few of coding rules. I started with vba and now I'm approaching to vb.net but my knowledge is very poor.

I wrote this function to extract a column from a recordset (query on DB) and put it into an Hashset of string.

Trying to handle errors on wrong number of column, I used these criteria:

1) declare "mErr" as boolean in code that calls the function;

2) send "mErr" byRef to the function;

3) when error occur: change mErr to true and insert into mHash an empty string.

Public Function RSCol(ByVal mRS As Object, ByVal mCol As Byte, ByRef mErr As Boolean)
    Dim i As Long
    Dim mHash As New HashSet(Of String)
    If mRS.GetUpperBound(0) < mCol Then
        mErr = True
        mHash.Add("")
        Return mHash
        Exit Function
    End If
    For i = 0 To mRS.GetUpperBound(1)
        mHash.Add(mRS(mCol, i))
    Next
    Return mHash
End Function

It seems to work but I think isn't a good coding and I would like to improve my coding skill.

Every suggest is appreciated.

Upvotes: 2

Views: 1968

Answers (4)

user4376581
user4376581

Reputation:

In your code :

Exit Function is unreachable since the Return statement above the Exit Function function will transfer the control out to the function.

More over a function should return a value otherwise you will get a warning. in such cases you can use Sub.

You code can be 

 Public Function RSCol(ByVal mRS As Object, ByVal mCol As Byte, ByRef mErr As Boolean) As HashSet(Of String)
        Dim loopCounter As Long
        Dim mHash As New HashSet(Of String)
        Try
            If mRS.GetUpperBound(0) < mCol Then
                Throw New Exception("")
            End If
            For loopCounter = 0 To mRS.GetUpperBound(1)
                mHash.Add(mRS(mCol, loopCounter))
            Next
        Catch ex As Exception
            mHash.Add(ex.ToString())
        End Try
        Return mHash
    End Function

You can refer Try..Catch mechanism in detail Click Here For more about Exceptions

Since i notice that your naming conventions are so poor i suggest you to go through this article by Microsoft

Upvotes: 1

Tharif
Tharif

Reputation: 13971

Before answering your question let me make clear about two things:

  1. Error
  2. Exception

Exceptions are those which can be handled at the run time whereas errors cannot be handled.

It is always a good practice to handle exception/errors effectively.

Here comes Try-Catch-Throw for our rescue.

Basic Syntax :

Try
    ' Do something in here that
    ' might raise an error.
  Catch
    ' Handle exceptions that occur within
    ' the Try block, here.
  Finally
    ' Perform cleanup code in here.
  End Try

Try: A Try block identifies a block of code for which particular exceptions will be activated. It's followed by one or more Catch blocks.

Catch: A program catches an exception with an exception handler at the place in a program where you want to handle the problem. The Catch keyword indicates the catching of an exception.

Finally: The Finally block is used to execute a given set of statements, whether an exception is thrown or not thrown. For example, if you open a file, it must be closed whether an exception is raised or not.

Throw: A program throws an exception when a problem shows up. This is done using a Throw keyword.

If you are not getting any exception in program also it is recommended to use the try catch blocks

Upvotes: 0

Btc Sources
Btc Sources

Reputation: 2061

You could use exceptions to control error on functions. When you detect something is going wrong within your function, you throw it:

if ( something ) then 'check if something bad happened
  Throw New Exception("X has occurred")
end if

Then, when this function which throw this exception, you should catch it like:

try
    ' Code with the call to the function which throws the exception
catch excp as Exception
    'Your control code for this situation, as example just show it
    MessageBox.show(excp.Message)
end

Upvotes: 0

Clijsters
Clijsters

Reputation: 4256

You should throw and handle Exceptions. Have a look at this.

Upvotes: 0

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