Professional IronPython

FIgURE 17-21: 
Select the Customers table for this example.
FIgURE 17-22: 
The data source
is ready to use in the example
extension.
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Using Visual Basic.NET for Database Support
 
❘
 
383
In order to get data from the database into the 
DataTable
object, the code calls the 
MyData.Fill()
method. Until the code calls this method, 
DS
contains all of the information about the Customers 
table, but none of the records.
Finally, the code calls the 
DS.FindByCustomerID()
method to find the record requested by the 
caller. The input argument to this method, 
Customer
, is a string that contains the 
CustomerID
field 
value. The output from the call is a 
NorthwindDataSet.CustomersRow
object, which is a special-
ized form of the 
DataRow
. Interestingly enough, IronPython can use the 
DataRow
directly without 
having to translate it in any way.
Accessing the database module through IronPython
The example extension has a method, 
GetData()
, that accepts a 
CustomerID
as input and provides 
a 
NorthwindDataSet.CustomersRow
as output. All you need now is some IronPython code to make 
the request and display the result. Listing 17-6 shows a typical example.
LISTINg 17-6: 
 Displaying a record onscreen
# Import the Common Language Runtime.
import clr
# Access the extension.
clr.AddReferenceToFile(‘Northwind.DLL’)
import Northwind
# Create an instance of the Northwind access object.
MyData = Northwind.DBAccess()
# Fill a row with data.
Row = MyData.GetData(‘ALFKI’)
# Display the data on screen. 
print ‘All the data for Customer ID ALFKI’
print ‘\nCustomer ID: ‘, Row.CustomerID
print ‘Company Name: ‘, Row.CompanyName
print ‘Contact Name: ‘, 
if Row.IsContactNameNull():
print ‘Nothing’
else:
print Row.ContactName
print ‘Contact Title: ‘, 
if Row.IsContactTitleNull():
print ‘Nothing’
else:
print Row.ContactTitle
print ‘Address: ‘, 
if Row.IsAddressNull():
print ‘Nothing’
continues
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