1. CIS266
FINAL REVIEW

2. Use the DataSet object
 To transfer data between tiers
 To manipulate the data without an open
connection
 To relate data from multiple sources
 To bind data to a Windows form

3. Referring to Records, Fields
 Actual data values are held in DataRow
objects
 Each Table object in a dataset has a DataRows
collection made up of DataRow objects
 Data values are held in the DataRow.Items
collection
 Refer to fields by index position or by name (string
value)

4. Setting a Relationship
 A DataRelation object describes the
relationship between the tables.
 Use the XML schema (.xsd) file for the dataset
to create the relationship – or – use code to
create a relation
 DataRelation Object Functions
 Relating tables
 Setting up constraints

5. Retrieving Related Row(s)
 Use the GetParentRow method to retrieve
the matching row from the table on the one
side
 The GetChildRows method returns an array of
rows from the many table
 May have 0, 1, or more related records
 Use Find method to find a row by its primary
key value

6. DataRowState Enumeration
 Used for finding, accessing changed rows
 The HasChanges Method determines if
changes have been made to a dataset
 Returns a boolean value
 The GetChanges Method is used to retrieve
datatable rows that have changes
 Use an empty argument to retrieve all changed
rows OR specify type of changes using
enumeration values

7. The Binding Source
 Controls record position within a table
 Assures that all bound controls on a form
display data from the same record
 Can bind controls in design time or in code

8. Binding Source Properties
 Position property holds the current row
number (zero based)
 Count property indicates the number of
records in a table
 The Current Property returns the current row

9. Binding Source Methods
 Binding Source Events
 The CurrentChanged event occurs when a
bound value is changed
 The PositionChanged event occurs when a
user navigates to another record

10. Adding an Event Handler
 An event handler executes automatically
when an event occurs.
 Need to write event handlers for objects
declared in code
 Write the procedure you want to execute when
the event occurs, including the sender and
eventargs arguments
 Add the handler in another procedure (such as
constructor), which is called a delegate
 turns the general procedure written into an event
procedure

11. DataRow Versions
 The DataRow object maintains several versions
of its column data
 Current, Original, Default, Proposed
 If no changes have been made, the Current and
Original versions are the same
 When EndEdit executes, the Current version is
replaced by the Proposed
 The EndEdit method confirms the changes
 Changes are made when the AcceptChanges
method executes

12. Changing Data
 Changes are made to the dataset, not to the
original data source.
 Execute the data adapter’s Update method
before calling the AcceptChanges method.

13. The AcceptChanges Method
 Calls the EndEdit method of the data row
 Removes all rows marked for deletion
 Makes the adds and edits indicated for the table
 Sets the Original version of each changed row to
the Current version
 Sets RowState of each row to Unchanged
 The RejectChanges replaces Current versions
with the Original versions
 After AcceptChanges or RejectChanges
executes, all RowState properties are reset to
Unchanged

14. Data Adapter Update Method
 Update writes the changes to the database
using SQL action queries
 Uses a group of Command Objects
 One each for insert, update and delete
 Can use actual queries or refer to stored
procedures

15. When to Update?
 Every time an add, edit, delete occurs?
 When the program terminates?
 Provide a Save option on a menu and prompt
for unsaved changes when the program
terminates?

16. Update Considerations
 Where does the application and data reside?
 How many users can make changes?
 Does the data source need to be up-to-date
at all times?

17. Concurrency
 Concurrency control is the process of handling
conflicts in updates by multiple users.
 Pessimistic concurrency control – a row is
unavailable from the time the record is retrieved
until the update is complete
 Optimistic concurrency control – a row is
unavailable only while an update is in progress
(default)
 “Last in wins” – A row is unavailable only when
the update is being made.

18. Parent/Child Relationships
 To maintain referential integrity, update in
the following order:
 Delete any child records
 Insert, update, and delete the parent records
 Insert and update the child records

19. Displaying Related Data
 Use a DataRelation
 Use GetChildRows/GetParentRow methods
 Use a Binding Source that uses a Datarelation as its
datasource
 Filter rows by
 Using a For loop and adding to an array or datable
 Use table.Select method
 Requery database for related records
 Use Parameter Query; or
 Use a variable and build a Select statement with
where clause

20. Stored Procedures
 Can store compiled SQL statement in
database
 Helps reduce security threats
 Can reduce data passed across network
 Typically work directly with a command
object
 Need to set command type
 Need to establish connection for command

21. Parameters
 Stored procedures accept and return values
through parameters
 Input parameters are similar to arguments in
procedural languages
 Command object has a parameters collection
to specify parameters to use with stored
procedure
 Can use parameters to pass criteria or values
to edit rows