1. 4: DataGrid, DataView, and ListView
Updated 9/12/2004
Copyright Scott-Jones Publishing, All rights reserved.

2. Overview DataGrid control DataViews and ListViews
Three-Tier Sports Rental Income
Sports Rental Checkout Example
Command Objects
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3. 4.1 DataGrid Control Spreadsheet-like view of a dataset Simple to use
Great for lists of data
Easily bound to a dataset
Provides “instant output”
Easy to customize and configure
Provides a convenient way to change data in a data set
Can change data simply by keying over it
Able to delete existing rows
Able to insert new rows
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4. DataGrid Properties Frequently used DataGrid properties:
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5. Rental Inventory DataGrid
Hands-on tutorial
Program: RentalInventory
Displays Items table from SportsRentals database in a DataGrid
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6. Rental Inventory Output
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7. Table and Column Styles
Configure the DataGrid's TableStyles property
for each column, set the HeaderText and Width
optional: align and format the column data
optional: remove row headers, make grid read-only
See the RentalInventoryColumns program
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8. Examples Original Data Grid Read Only with Row Selector Removed
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9. DataGrid Events Click Event
fires when user clicks on row selector
use CurrentRowIndex to obtain dataset row:
Dim drItem As DataRow = _
DsItems1.Items(dgdInventory.CurrentRowIndex)
To delete the selected row of the dataset above
drItem.Delete()
To update a field in the dataset selected row
drItem(“Amount”) = txtAmount.text
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10. Karate Updates Example
Program: KarateUpdates
Actions:
displays the Payments table
user can delete a payment
user can select a payment and modify the amount
underlying database can be updated
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11. DataGrid Tips
Alter field order in data adapter's SELECT statement to change default column order in DataGrid
Define table styles and column styles for complete control over DataGrid columns
Write code in CurrentCellChanged event to prevent user from modifying a column
dgdItems.ReadOnly = _ (dgdItems.CurrentCell.ColumnNumber = 0)
Bind grid to dataset in Visual Studio (DataSource prop)
Or bind grid to dataset in code
dgdPayments.SetDataBinding(DsPayments1, “Payments")
-or- dgdPayments.DataSource = dsPayments1
dgdPayments.DataMember = “Payments”
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12. 4.2 DataViews and ListViews
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13. DataView Control Sorts and/or filters a dataset
Drag the DataView control from the Toolbox Data section to a form
Important properties:
Table: dataset & table containing the data (dsMbrs1.Mbrs)
Sort: field (column) name to be sorted (can use DESC)
RowFilter: a selection expression such as “Salary>30000”
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14. Accessing a DataRow Accessing LastName column of row 0 of the DataView
txtName.Text = dvMembers(0).Item("LastName")
Each row is a DataRowView object
Dim a DataRow and get row 0 from the DataView:
Dim row As DataRowView = dvMembers(0)
Use the DataRow to get contents of the LastName column:
txtName.Text = row("LastName")
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15. Filling a ListView Control
Excellent for displaying database tables
Very flexible
Looks like a DataGrid
No data binding
Fill from either dataset or DataView
Example:
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16. ListView's Structure Items collection holds the rows
Each row is a ListViewItem object
In each row:
Text property holds first column
SubItems collection holds the other columns
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17. Example: Filling a ListView
lvwPayments.Items.Clear()
Dim count As Integer = dvPayments.Count
Dim i As Integer
Dim item As ListViewItem
For i = 0 To count - 1
With dvPayments(i)
item = New ListViewItem(Format(.Item("PaymentDate"), _
" MM/dd/yyyy"))
lvwPayments.Items.Add(item)
item.SubItems.Add(.Item("MemberId"))
item.SubItems.Add(FormatNumber(.Item("Amount")))
End With
Next i
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18. Karate School Payments
Hands-on tutorial
Program: KaratePayments
Fills a ListView from a DataView
Sorts on any column, both directions, when user clicks on column header
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19. 4.3 Three-Tier Sports Rental Income
Hands-on tutorial
Program: RentalIncome
Displays and calculates from the Items table
estimates income based on rental rates and inventory
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20. Class Design Implements a Three-Tier model (see Chapter 1)
Data tier – SportsRental class
Business tier – Items class
application-specific calculations
Presentation tier – frmRentalIncome class
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21. 4.4 Sports Rental Checkout Example
Program: RentalCheckout
Emphasis on object-oriented design
Checks out rental items from a Sports Rental store
Design tool: Use-case scenario
describes interaction between user and program
lists anticipated inputs and outcomes
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22. Subtasks User enters a username and password
Clerk creates a Rental Invoice
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23. Subtask: Clerk enters username, password
Program displays a dialog window containing a list of employee names.
The clerk selects a name from the list and inputs a corresponding user password.
The program checks the password against the database and does one of the following:
If the password is correct, the program closes the login window and proceeds to the next subtask.
If the password is incorrect, the program displays an error message and asks the clerk to reenter the password. The clerk is given three tries before the program ends.
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24. 4.5 Command Objects
Visual Studio creates four commands for each data adapter:
SelectCommand
InsertCommand
UpdateCommand
DeleteCommand
Primary key required for all but SelectCommand
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25. Parameters Collection
Each Command object has a Parameters collection
Examples:
Reference the collection:
daPayments.InsertCommand.Parameters
Assign value to a parameter:
With daPayments.InsertCommand
.Parameters("Date").Value = txtDate.Text
End With
Get parameter's name:
Dim param As OleDbParameter
param = daPayments.InsertCommand.Parameters(0)
param.ParameterName
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26. OleDbParameter Properties
Direction: Indicates if parameter is input-only, output-only, bidirectional, or a stored procedure return value parameter.
IsNullable: Indicates whether parameter accepts null values.
Precision: Max digits used to represent Value property.
Scale: Number of decimal places to which Value is resolved.
Size: Max size, in bytes, of data within column.
SourceColumn: Name of source column mapped to DataSet, used for loading or returning value.
Value: The value of the parameter.
For SQL Server, see the SqlParameter class.
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27. Direct Update Approach
Updates database directly, bypassing dataset
Careful: there is no "undo"
Other database users get the very latest data
Potential for more network traffic
when multiple operations execute
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28. Command Object
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29. Karate Commands Example
Program: KarateCommands
Displays contents of the Select, Insert, Delete, and Update command objects
created by Visual Studio for the daPayments data adapter
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30. Inserting Table Rows General format Example INSERT INTO target
[(field1[,field2[,...]])]
VALUES(value1,[,value2[,...])
Example
INSERT INTO Payroll (SSN, PaymentDate,
HoursWorked, HourlyRate)
VALUES(' ', #1/15/1998#, 47.5, 17.50)
optional
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31. Query Parameters Make queries more flexible
Avoid messy embedding of variable names inside SQL code
Microsoft Access Example:
INSERT INTO Payments( Amount, MemberId, PaymentDate )
VALUES (?, ?, ?)
SQL Server Example:
@PaymentDate)
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32. Executing Commands Open the database connection
Assign value to each parameters
Call ExecuteNonQuery
Close the connection
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33. InsertCommand Example
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34. Updating Table Rows Use the WHERE clause, or all rows will be updated!
General format
UPDATE table
SET fieldname = newvalue
[ SET fieldname = newvalue ] ...
WHERE criteria
Example
UPDATE Payroll
SET HourlyRate = HourlyRate * 1.05
WHERE PaymentDate > #05/01/1999#
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35. Deleting Table Rows Use the WHERE clause, or all rows will be deleted!
General format
DELETE
FROM table
WHERE criteria
Example
DELETE FROM Payroll
WHERE PaymentDate < #1/1/1998#
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36. Inserting Karate Payments
Example program: KarateInsertPayments
Uses a Command object to execute an INSERT query
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37. The End
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