Question

i am trying to write an mdb to CVS converter with vb.net.
i want to get the columns header names using the oledbdata reader and here is my code so far

 Public Cheadernames As Array
    Public firstRead As Boolean = False
    Public columnCount

    Dim connectionstring = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & strfilename
    Dim queryString = "SELECT * FROM products"
    Dim connection As New OleDbConnection(connectionstring)
    Dim command As New OleDbCommand(queryString, connection)
    connection.Open()
    Dim reader As OleDbDataReader = command.ExecuteReader()
    While reader.Read
        If firstRead Then
            columnCount = reader.FieldCount()
            firstRead = False
            For i = 0 To columnCount - 1
                Cheadernames(i) = reader.GetName(i) ' i am getting an error with this line
                Console.WriteLine(Cheadernames(i))
            Next
        End If

so i am trying to put all column headers names in an array but the commented line gives me this error “Object variable or With block variable not set”

Answer 1

Your Cheadernames variable is an empty array, with no elements and no type. That’s just wrong: you should almost never declare a variable or method parameter “As Array”. Instead, you want something like this:

Private HeaderHames() As String
Private firstRead As Boolean = True
Private columnCount As Integer

Dim connectionstring = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & strfilename
Dim queryString = "SELECT * FROM products"
Using connection As New OleDbConnection(connectionstring), _ 
      command As New OleDbCommand(queryString, connection)

    connection.Open()
    Using reader As OleDbDataReader = command.ExecuteReader()
        While reader.Read
            If firstRead Then
                columnCount = reader.FieldCount()
                HeaderNames = New String(columnCount-1)
                firstRead = False
                For i = 0 To columnCount - 1
                    HeaderNames(i) = reader.GetName(i) 
                    Console.WriteLine(HeaderNames(i))
                Next
            End If
            '...
         End While
     End Using
 End Using