Creating Active X DLL

CoolEJ · November 28th, 2007, 11:15 PM

Hi, I currently have a database with multiple tables.
I need to create an Active X (VB6) to update fields with data from fields on another table.

Example:
Field 1 from Table 1 is updated with data from Field3 Table 2.

Please help me to create this one.

Thanks,
Eric

EJC

gbianchi · November 29th, 2007, 08:32 AM

well.. you can execute a query to do this:

UPDATE table1 SET field1 = (SELECT field3 FROM table2 WHERE (something that return only 1 row of data))

HTH

Gonzalo

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CoolEJ · November 29th, 2007, 08:44 AM

Hi,

Thanks for the reply. That's SQL statement and I can handle that.

My problem is more on how to use VB6 ActiveX DLL to connect to the database and execute that SQL statement.

Please help me out.

Thanks

EJC

gbianchi · November 29th, 2007, 08:58 AM

A activeX DLL could be an exe that run alone.. or you have to call it from another program???

HTH

Gonzalo

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woodyz · November 29th, 2007, 02:54 PM

It would be helpful if you could be specific about what problems you are having.

Are you familiar with making ActiveX dlls in VB6? As you are probably aware, VB6 makes this very simple. Let us know if this is where you need guidance, and what exactly you are having trouble with.

The basics of creating a dll are as follows:
- Start up a new project, and select the ActiveX dll icon to create a project.
- Put your code into the class provided - but give the class a name that has meaning to your project.
- Yoo have to have public properties and methods (functions or subs) for the class to be useful (or to even compile if I remember correctly).

To test this new dll, you can add a standard exe project to the project group (using the main menu > add project dialog) and set it as the start-up project. You will then need to add a reference to the dll in project > references, and write some code to use the dll.

Once everything is done, you will need to provide an installer that your users will use to install the dll on their computer.

That is pretty much the basics - I left out all the details.

If this is your first project devloping COM dlls, you are in for a lot of fun. And I am using the word fun to mean "headaches". Of course, for most of us the issues with COM dlls are slowly fading into history since a new mechanism for RPC is used in the .NET world. We still have dlls, but now the are "managed" and do not use the registry for locating them (as well as a lot of other changes).

Woody Z
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CoolEJ · November 29th, 2007, 10:24 PM

Hi,
I'm calling this from another program. This program only works with VB6.0 DLLs.

I'm using a SQL database and it's my first time dealing with VB 6.0.
My SQL database has two tables. Let's name it table 1 and table 2. When a record is created in Table 2, I want a DLL to update a field(Let's say field1) in Table 1 with the data(Let's say field999) from the new record added in Table 2.

I can execute it in stored procedure but the program is presently limited to VB6.0 ActiveX DLL.

To do this (I think):
1. the DLL must connect to the database
2. Execute the SQL Statement (Update etc...)

I need help for no.1 and I haven't seen an actual ActiveX with SQL statements in it before. Maybe an example too?

I'd highly appreciate this.

EJC

gbianchi · November 29th, 2007, 10:27 PM

well.. conecting a dll is the same as conecting any exe file.. you should google about how to connect to a database in vb6...

HTH

Gonzalo

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================================================== =========
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woodyz · November 30th, 2007, 02:29 PM

Here is a very minimal example.
Get this to work, and then let us know what you are having trouble with.

Note that this example uses a database named wroxtest.mdb, which has a table named Vocabulary with 3 columns:
1 - Id (autonumber0
2 - Name (a text field)
3 - Description (a text field)

Your dll project must have a reference to the ADODB dll.

Code:

Public Function DoDataWork(ByVal name As String, ByVal description As String) As Integer
    ' Your connection object
    Dim cn As ADODB.Connection    
    ' You can get back the number of records affected, so we will put it into a variable named result.
    Dim result As Integer

    ' Instantiate the connection
    Set cn = New ADODB.Connection
    ' Assign the connection string
    cn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & App.Path & "\wroxtest.mdb;"
    ' And, guess what?  Open the connectino
    cn.Open
 
    ' A simple insert statement
    cn.Execute "Insert Into vocabulary (Name, Description) Values ('" & name & "', '" & description & "')", result

    ' Always close your connection - this is imoprtant
    cn.Close

    ' Result will always contain one in our little example
    DoDataWork = result
End Function

Of course, you now need some code to instantiate and use your new dll.

Woody Z
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