Author: Iqbal M. Khan
The .NET framework provides a very flexible and powerful approach to databinding that cuts down a lot of redundant code and simplifies the development process significantly. Unlike the earlier databinding models, which were limited to single data source, the .NET framework provides read/write (two ways) link to a large number of data sources such as DataSets, DataTables, Collections and also textboxes, checkboxes, radio buttons and so on.
In the following object binding example you'll see how easy it is to implement a record navigation with TierDeveloper generated objects with single line of hand-written code. Let's say you've three textbox controls on a win form and you loaded all customers in a collection by calling getAll method of customers factory class.
Here is how you might want to load customers and then bind the attributes to text controls (in your case you might have datagrid or other UI components)
Public csColl As CustomersCollection Private Sub btnLoad_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLoad.Click Dim objCustomer As Customers = New Customers Dim objFactory As CustomersFactory = New CustomersFactory csColl = New CustomersCollection csColl = objFactory.getAll() txtCustomerId.DataBindings.Add("Text", csColl, "CustomerID") txtCompanyName.DataBindings.Add("Text", csColl, "CompanyName") txtContactTitle.DataBindings.Add("Text", csColl, "ContactTitle") End Sub
The CurrencyManager is used to keep data-bound controls synchronized with each other. The Position property of CurrencyManager is used to determine the current position of all controls. Your click event handler for Next button might look like this:
Private Sub btnNext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnNext.Click Dim cm As CurrencyManager = CType(Me.BindingContext(csColl), CurrencyManager) If cm.Position < cm.Count - 1 Then cm.Position += 1 End If End Sub Private Sub btnPrev_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPrev.Click Dim cm As CurrencyManager = CType(Me.BindingContext(csColl), CurrencyManager) If cm.Position > 0 Then cm.Position -= 1 End If End Sub
You might allow users to make changes to any records and then persist those changes when the user clicks SAVE button. Your click event handler for Save button might persist the changes with a single call as illustrated below.
Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click Dim cf As CustomersFactory = New CustomersFactory cf.Save(csColl, 0) End Sub
Author: Iqbal M. Khan works for Alachisoft, a leading software company providing .NET and Java distributed caching, O/R Mapping and SharePoint Storage Optimization solutions. You can reach him at firstname.lastname@example.org.