Question

This function is in a Class file in App_Code folder

 Public Shared Function CRUD(ByVal _sql As String, ByVal _parameterNames() As String, ByVal _parameterVals() As String) As Integer
        Dim _noOfRowsAffected As Integer
        Dim _connection As SqlConnection = Global.Connection.GetDbConnection()
        Dim _command As New SqlCommand(_sql, _connection)

        Try
            If _parameterNames IsNot Nothing Then
                For i = 0 To _parameterNames.Length - 1
                    _command.Parameters.AddWithValue(_parameterNames(i), _parameterVals(i))
                Next
            End If

            _noOfRowsAffected = _command.ExecuteNonQuery()
        Catch ex As Exception
            'MsgBox(ex.Message)
            _noOfRowsAffected = -1
        Finally
            If _connection.State = ConnectionState.Open Then
                _connection.Close()
                _connection.Dispose()
                _command.Dispose()
            End If
        End Try

        Return _noOfRowsAffected
    End Function

This code is in aspx.vb page

Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSave.Click
        Dim _parameterNames(6), _parameterVals(6) As String
        _parameterNames(0) = "@Name"
        _parameterVals(0) = txtCoachingName.Text
        _parameterNames(1) = "@Address"
        _parameterVals(1) = txtCoachingAddress.Text
        _parameterNames(2) = "@Mob1"
        _parameterVals(2) = txtCoachingMob1.Text
        _parameterNames(3) = "@Mob2"
        _parameterVals(3) = txtCoachingMob2.Text
        _parameterNames(4) = "@LLine"
        _parameterVals(4) = txtCoachingLLine.Text
        _parameterNames(5) = "@Established"
        _parameterVals(5) = ddlCoachingEstablished.SelectedValue
        _parameterNames(6) = "@DemoVideo"
        _parameterVals(6) = txtCoachingDemoVideo.Text
        _parameterNames(7) = "@Password"
        _parameterVals(7) = txtCoachingPassword.Text
         Try
        DataAccess.CRUD("UPDATE CoachingDetails SET Name=@Name,Address=@Address,Mob1=@Mob1,Mob2=@Mob2,L_Line=@LLine,Established=@Established,Demo_Video=@DemoVideo,Password=@Password,Step_Completed='True',Time_Stamp='" & Date.Now & "'", _parameterNames, _parameterVals)
    Catch ex As Exception

    End Try

Now i want to catch the Primary Key Violation exception in my aspx.vb page..but i do not get the exception in the aspx.vb page as the error is caught by the class function.So, how do i get the exception from the class file to the aspx.vb file??
End Sub

Answer 1

Rethrow. (http://www.selfelected.com/rethrow/)

Try
    ....
Catch ex As Exception 
    do some stuff with ex
    Throw    ' important to not use ex as parameter as that would start a new exception stack.
Finally
    do some other stuff
End Try

Since you don’t do anything in the catch just skip it.

Try
    ....
Finally
    do some other stuff
End Try

To make the code nicer read up on Using. With Using you can have the compiler insert the Try/Finally implicitly for you. The code will be something like:

Using connection As SqlConnection = Global.Connection.GetDbConnection()
    Using command As New SqlCommand(sql, connection)
        If parameterNames IsNot Nothing Then
            For i = 0 To parameterNames.Length - 1
                command.Parameters.AddWithValue(parameterNames(i), parameterVals(i))
            Next
        End If
        noOfRowsAffected = _command.ExecuteNonQuery()
    End Using
End Using

Please note that I made all your variables local. This might not be possible for you since you know a lot more about your code than I do… (but the code suggested that your variables where class variables but you treated them as local anyway.)

Also check out Dapper. Dapper is what Stack overflow runs on. It is a nice small lib for making writing sql calls easier to write and read.