ADO Data Control
Visual Basic 6 gives us the choice of technique when programming with database, or use DAO as in the previous two articles, or are using ADO (ActiveX Data Objects) .
The main difference between ADO and the ADO DAO allows us to work with any type of data sources (data sources), not necessarily the Access database or ODBC. Data sources can be a list of email addresses, or a text string, where each row is a record consisting of fields separated by commas ( comma separated values ).
If the DAO is used directly in the name of the Database MSAccess ADO us connected (connect) a database through a Connection by specifying a Connection String . In the Connection String Database Provider (such as Jet, ISAM, Oracle, SQLServer, etc. ..), Database name, username / password logon to a database. etc. Then we can retrieve (extract) the recordsets and update the records using the SQL command used on the tables or stored procedures inside the database.
Normally, when I booted a new VB6 project, Control Data ADO is not available in the IDE. Wanted it, use the Command Menu Project | Components ... , then select Microsoft ADO Data Control 6.0 (OLEDB) from Interface Components, as follows:
The main difference between ADO and the ADO DAO allows us to work with any type of data sources (data sources), not necessarily the Access database or ODBC. Data sources can be a list of email addresses, or a text string, where each row is a record consisting of fields separated by commas ( comma separated values ).
If the DAO is used directly in the name of the Database MSAccess ADO us connected (connect) a database through a Connection by specifying a Connection String . In the Connection String Database Provider (such as Jet, ISAM, Oracle, SQLServer, etc. ..), Database name, username / password logon to a database. etc. Then we can retrieve (extract) the recordsets and update the records using the SQL command used on the tables or stored procedures inside the database.
Normally, when I booted a new VB6 project, Control Data ADO is not available in the IDE. Wanted it, use the Command Menu Project | Components ... , then select Microsoft ADO Data Control 6.0 (OLEDB) from Interface Components, as follows:
Begin a new VB6 project, giving it the name ADODataControl by clicking project name in Project Explorer right then edit the Name property in the Properties Window. This form of the name of frmADO , and review questions DataControl Demo ADO in its Caption.
DoubleClick read Icon cua trong ADO Data Control Toolbox. ADO Data Control Mot has Adodc1 to train hyena ra Form. Muon nam and node to dưới Form, Nhu mot giong StatusBar there in September Align property node trong cua Thanh Properties Window 2 - vbAlignBottom .
Click on the right of property (Custom) , and then click on the browse button with three dots to communicate voice Property Pages appear. In the dialog, on the General tab select the Radio (Option) Button Use Connection String and click the button ... Build .
In the Data Link Properties dialog, Provider tab, select Microsoft Jet OLE DB Provider3:51, and then click the Next button>> or the Connection tab.
DoubleClick read Icon cua trong ADO Data Control Toolbox. ADO Data Control Mot has Adodc1 to train hyena ra Form. Muon nam and node to dưới Form, Nhu mot giong StatusBar there in September Align property node trong cua Thanh Properties Window 2 - vbAlignBottom .
Click on the right of property (Custom) , and then click on the browse button with three dots to communicate voice Property Pages appear. In the dialog, on the General tab select the Radio (Option) Button Use Connection String and click the button ... Build .
 | This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (842x574) |
In the Data Link Properties dialog, Provider tab, select Microsoft Jet OLE DB Provider3:51, and then click the Next button>> or the Connection tab.
In the Select or enter a place name database we choose E: \ Program Files \ MicrosoftVisual Studio \ VB98 \ BIBLIO.MDB, in your computer that you can file on disk C or D.Then, you can click the Test Connection button below to see connection is not well established.
Up connection is finished, we just want to get anything done Recordset by clicking on Recordsource property of Adodc1. In the Property Pages of it select 2-adCmdTable as Command Type , and then open the combo box for the Table or Stored Procedure Name to select the Titles table .
Depending on how you use the ADO Recordset, it has three types and is called the Cursor Type . Cursor is simply another name for the recordset:
| This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (907x468) |
Up connection is finished, we just want to get anything done Recordset by clicking on Recordsource property of Adodc1. In the Property Pages of it select 2-adCmdTable as Command Type , and then open the combo box for the Table or Stored Procedure Name to select the Titles table .
| This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (763x319) |
Depending on how you use the ADO Recordset, it has three types and is called the Cursor Type . Cursor is simply another name for the recordset:
- Static Cursor: Static Cursor give you a static copy (copies rigid) of the records. Static Cursor while you are using, if anyone else modify or add or subtract anything to the recordset you will not see.
- Keyset Cursor: Keysey Static Cursor Cursor over the place while you use it, if anyone has changed any record you'll know. If you delete one record, you will not see it anymore. But you will not know if anyone does add a record to the recordset.
- Dynamic Cursor: As the word alive (dynamic) implies that, while you are using a Dynamic Cursor, if anyone else modify or add or subtract anything to the recordset you will find out.
Now you put labels on Form 4 with Captions: Title, Year Published, ISBN, and PublisherID. Then add 4 textboxes and named them respectively as txtTitle, txtYearPublished,txtISBN vatxtPublisherID.
Data Binding to perform, select the textbox txtYearPublished (year of publication), then set the DataSource property in the Properties Window to its Adodc1 . When you click on the DataField property of the ComboBox txtYearPublished open and you will see listed the names of the Fields in the Titles table. That's because Adodc1 considered taking intermediate Titles table from the database. Here we will choose Year Published column.
Repeat this for the other three textboxes, and select the column title (title), ISBN (the number of international tourism in the library), and PubID (publisher of history) as the DataField for them.
Data Binding to perform, select the textbox txtYearPublished (year of publication), then set the DataSource property in the Properties Window to its Adodc1 . When you click on the DataField property of the ComboBox txtYearPublished open and you will see listed the names of the Fields in the Titles table. That's because Adodc1 considered taking intermediate Titles table from the database. Here we will choose Year Published column.
Repeat this for the other three textboxes, and select the column title (title), ISBN (the number of international tourism in the library), and PubID (publisher of history) as the DataField for them.
Here, although not written a line of code, you can run the program and it will show as below:
This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (704x392)
You can download the program uses ADO Data Control this from here ADODatacontrol.zip .
Now let's start a new standard VB6 project, named ADOClass MS Access file and copy BIBLIO.MDB, ie database, into the same folder of this new project.
Want to use the Data Form Wizard, we must add it to your development environment (IDE) for VB6. You use the Command Menu IDE Add-Ins | Add-In Manager ... . Choose the VB6 Data Form Wizard in the delivery device, and then click Checkbox Loaded / unloaded to loaded words right out of "VB6 Data Form Wizard" as shown in the image below:
Data Form Wizard
To help programmers design of data forms faster, for our VB6 Data Form Wizard to generate (produce) a form that supports Edit, Add and Delete records.Now let's start a new standard VB6 project, named ADOClass MS Access file and copy BIBLIO.MDB, ie database, into the same folder of this new project.
Want to use the Data Form Wizard, we must add it to your development environment (IDE) for VB6. You use the Command Menu IDE Add-Ins | Add-In Manager ... . Choose the VB6 Data Form Wizard in the delivery device, and then click Checkbox Loaded / unloaded to loaded words right out of "VB6 Data Form Wizard" as shown in the image below:
If you want every time you start VB6 IDE is available in the Data Form Wizard Add-Ins menu option, in addition Loaded, additional check box you click the Load on Startup .
An Add-In is a new menu item, which can be added to an application program is available. Usually, people use the Add-Ins to add functionality to a program, do as the program functions that are available from the beginning. Try to start the Data Form Wizard from the Command Menu new IDE Add-Ins | Data Form Wizard ...
An Add-In is a new menu item, which can be added to an application program is available. Usually, people use the Add-Ins to add functionality to a program, do as the program functions that are available from the beginning. Try to start the Data Form Wizard from the Command Menu new IDE Add-Ins | Data Form Wizard ...
When the Data Form Wizard page - Introduction appears, click Next
In the next page to select the Access Database Type.
In the Database page, click Browse to select an MS Access database file. Here weselect the file from the folder BIBLIO.MDB of this program. Paragraph click Next.
In the form, we choose the Single Record Form Layout and Binding Class for Type.ClickNext segment. If we choose the ADO Data Control, the result will look like when weuse the DAO Data Control as in a previous post.
In the Record Source I select the Titles table. Fields Available listbox displays the fieldsof the Titles table. After selecting a field by clicking on the Listbox field names that, if youclick the triangle to the right, the only field names that will be moved through the bottomof the right Listbox Selected Fields.
If you double click the triangle just to the right, then all fields will also be moved back to the left to the right.You can also arrange the location of the selected fields by clicking on the name field and click the arrow was pointing up or down to move it up field or down the list of fields.
Also, select Title to Column to Sort By a Combobox's in it for the records in the recordset are arranged in alphabetical order (Alphabetical order) of the title field (Title).
If you double click the triangle just to the right, then all fields will also be moved back to the left to the right.You can also arrange the location of the selected fields by clicking on the name field and click the arrow was pointing up or down to move it up field or down the list of fields.
Also, select Title to Column to Sort By a Combobox's in it for the records in the recordset are arranged in alphabetical order (Alphabetical order) of the title field (Title).
Control Selection page, we will for medical reasons to have all the buttons. Please click Next .
Upon termination of the Data Form Wizard, it will generate frmADODataForm form.Please remove Form1 Command Menu and use Project | Properties ...ADODataControl Change the Startup Object to frmADODataForm. The finish istemporary program to edit the records of the Titles table.
We look at the Form and the Data Form Wizard code is generated. InfrmADODataForm, an array of textboxes do txtFields name. All textboxes are setDataField property of the table field names Titles. For example txtFields (2) there areDataField ISBN. The main form is not used, but using an ADO Data Control Object ofclass clsTitles.
Initialisation of the class is part clsTitles Open a Connection and take on a datasetcalled DataMember laPrimary as follows:
The locations of the database, if you do not want it stuck in a folder, use App.Path to determine the relationship between the location of the database and the folder of the program is running, for example:
In Sub Form_Load , we can use For Each to go through all the textboxes in array txtFields. Because the DataSource property of a textbox so we use the keyword Object Set it to point to Object PrimaryCLS. Simultaneously, we also must specify the name of each textbox is DataMember Primary:
I want to handle the Event of clsTitles adoPrimaryRS declare recordset with WithEvents:
And we also have to declare in Form (object clsTitles) PrimaryCLS with WithEvents:
Initialisation of the class is part clsTitles Open a Connection and take on a datasetcalled DataMember laPrimary as follows:
Private Sub Class_Initialize()
Dim db As Connection
Set db = New Connection
db.CursorLocation = adUseClient
' Open connection
db.Open "PROVIDER=Microsoft.Jet.OLEDB.3.51;Data Source=E:\Websites\Vovisoft\VisualBasic\ADOForm\BIBLIO.MDB;"
' Instantiate ADO recordset
Set adoPrimaryRS = New Recordset
' Retrieve data for Recordset
adoPrimaryRS.Open "select Title,[Year Published],ISBN,Description,Notes,PubID from Titles Order by Title", _
db, adOpenStatic, adLockOptimistic
' Define the only data member, named Primary
DataMembers.Add "Primary"
End Sub |
db.Open "PROVIDER=Microsoft.Jet.OLEDB.3.51;Data Source=" & App.Path & "\BIBLIO.MDB;" |
When moving from record to record this other end, the Recordset can raise MoveComplete Event . Event was being handled (resolved) in the class by re-raise clsTitles Event MoveComplete so it is handled in the form.
Private Sub Form_Load() ' Instantiate an Object of class clsTitles Set PrimaryCLS = New clsTitles Dim oText As TextBox ' Iterate through each textbox in the array txtFields 'Bind the text boxes to the data source, i.e. PrimaryCLS For Each oText In Me.txtFields oText.DataMember = "Primary" ' Use Set because property Datasource is an Object Set oText.DataSource = PrimaryCLS Next End Sub
I want to handle the Event of clsTitles adoPrimaryRS declare recordset with WithEvents:
Dim WithEvents adoPrimaryRS As Recordset Private Sub adoPrimaryRS_MoveComplete(ByVal adReason As ADODB.EventReasonEnum, _ ByVal pError As ADODB.Error, adStatus As ADODB.EventStatusEnum, ByVal pRecordset As ADODB.Recordset) ' Raise event to be handled by main form RaiseEvent MoveComplete End Sub |
In Form, Event MoveComplete would show absolute position (Absolute Position) ofrecord with the code below:
Private WithEvents PrimaryCLS As clsTitles
When the user clicks Refresh , the textboxes will be displayed again with the latest details of the record from the recordset, when someone else missed the modified record. Requery Method of clsTitles calling Requery method of the recordset as follows:
You can download this program from here ADOClass.zip .
(Collected)
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