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Simplify
your life with Object Binding
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)
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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:
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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.
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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 |
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