vb.net 2003 simple access mdb example? Anywhere?

vb.net 2003 simple access mdb example? Anywhere?

• mr_c

  How is this,

  VB.NET: An unhandled exception of type 'System.Data.OleDb.OleDbException' occurred in system.data.dll
  

  superior to this:

  VB6: Runtime error '-2147217865 (80040e37)'; Table 'account' doesn't exist

  In the VB.net case, I'm left scratching my head with only the vaguest idea where to look. In the VB6 case, I'm told exactly what silly mistake I just made. Its the difference between hours of missing the painfully obvious and 10 seconds to switch to the right database. I don't see how devolving the error reporting feature can be considered progress.

  This disagreement aside, thank you for the example as it is exactly what I needed to get me started! Too often examples are so fleshed out with all sorts of bells and whistlles that its difficult to see the basic idea inside all the code.

  
  

• ferlinco

  Ok, I went back to VB6 and coded the same basic program (open the DB and stuff a combobox. VB6 told me immediately what the problem was - table does not exist in database. Dummy me, the connection as to a different mdb file than what I thought.

  So why is it that ancient old vb6 could just pop up and tell me whats wrong when vb.net could only tell me an exception occured This is what MS considers progress

  I remember upgrading from VB4( ) to VB6. Sure, things were hard to figure out at first but everything was actually *better*. Going from VB6 to vb.net feels like the exact opposite.

  
  

• soanfu

  do you mean getting the data from MS Access and putting it into a combobox if so this almost has it with some modifications to be made for you...

  http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=868748&SiteID=1

  use OleDb instead of Sql classes so a conversion for you would be this pretty much...import the System.Data.OleDb namespace then...

  
  
  Dim theOleDbCommand as new OleDbCommand("SELECT [fieldName] FROM [TableName]", new OleDbConnection(connectionString))
  Dim theDataSet as new DataSet()
  Dim theDataAdapter as new OleDbDataAdapter(theOleDbCommand)
  theDataAdapter.Fill(theDataSet)
  
  
  Me.cmbNames.DataSource = theDataSet.Tables(0).DefaultView
  Me.cmbNames.DisplayMember = "FieldName"

  And thats it! You could also do it this way, which would be better in a sense if you are not going to be re-using the dataset for other operations/look ups.

  
  

  Dim theOleDbCommand as new OleDbCommand("SELECT [fieldName] FROM [TableName]", new OleDbConnection(connectionString))
  

  theOleDbCommand.Connection.Open()

  Dim theReader as OleDbDataReader = theOleDbCommand.ExecuteReader(CommandBehavior.CloseConnection)

  while theReader.Read() = true

  Me.theComboBox.Items.Add(theReader(0).ToString())

  end while
  

  this will read data line by line and add items retrieves from the first column into the combobox.
  

  
  
  

• R.Tutus

  What's the inner exception my code was just a snippet example but you should always put try catch blocks around the code to catch any errors and handle them. What is the inner exception thrown I would also suggest placing the square brackets around the fieldname and table name to "escape" from any special meaning the words may have, as I have done in my example
  
  

• PQSIK

  :-) not at all, its good talking about it and sharing views. The platform changes and so does the lifecycle, decisions are made for one reason or another etc.... At least in the .NET, you know exactly where the problem is appearing from in that if its a database problem (oledb) however you should be catching exceptions (or on error goto statements in VB for example). usually you would recieve a JIT giving you the error details on where its coming from, at what line of code, what the specific exception was (inner exception), stack trace etc....
  
  

• gfmajchrzak

  exceptions are pretty much generally runtime errors giving you the specific error that occurs, its better than just having "runtime error 5 type mismatch" errors in VB6
  
  

• bjquinniii

  in what way it will throw a runtime error yes with errors but it would be very unfriendly and unprofessional therefore the try catch blocks are used to handle them, deal with it in your own way and perhaps show the user a more friendly error message in the catch block
  
  

• Penicillin

  Fails a the Dim theRead line with "An unhandled exception of type 'System.Data.OleDb.OleDbException' occurred in system.data.dll"

  I'm looking at the error messages and cannot make heads not tails of what is supposed to be wrong other than that it says the oledbcommand = nothing (expected since the dim failed).

  I used the server explorer to create an oledbconnection to an existing access database then copied the connection string from it into the new oledbconnection below, I figure that would be a foolproof way to get the connection string (included password too).

  Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

  Dim theOleDbCommand As New OleDb.OleDbCommand("SELECT name FROM account", New OleDb.OleDbConnection("see above"))

  theOleDbCommand.Connection.Open()

  Dim theReader As OleDb.OleDbDataReader = theOleDbCommand.ExecuteReader(CommandBehavior.CloseConnection) '<< Fails

  While theReader.Read() = True

  Me.thecombobox.Items.Add(theReader(0).ToString())

  End While

  'this will read data line by line and add items retrieves from the first column into the combobox.

  End Sub

  
  

• TigerPhoenix

  I found it easier in VB6 to leave the On Error stuff until after I'd gotten something working as VB6 typically told me enough on its own to let me find and fix the problem. I added the On Error stuff later to prevent ungraceful and/or unnecessary exits.

  Is vb.net not capable of describing errors without user's coding everything in themselves

  
  
• vb.net 2003 simple access mdb example? Anywhere?