1. Unit 9.1 Learning Objectives Data Access in Code
Data Access in Design (Review)
Five Step Sequence
Hands-on

2. the ConnectionString (e.g. csFees)
sqlDataSource (GUI)
the SQL command
the ConnectionString (e.g. csFees)

3. GUI Views DetailsView FormView GridView DataList ListView
Number of records
One
Many
Insert
Yes No
Edit/Update
Delete
Column Format

4. Accessing Data Database server SQL e.g. MS SQL Server
SqlDataSource
Database location (Connectionstring)
What data (Command)
What technology (Namespaces)
Run! (DataReader)
Browser e.g. FireFox
Web server
e.g. Windows
Server
Database server
e.g. MS SQL Server
HTML
ASPX
SQL
["1",“Registration Fee",5.00,”2”, “Vehicle License Fee",7.5,”3”, “Weight Fee“, ]
Parse (Loop in Reader)

5. Five Steps to Data in code
The Five Step Plan
Setup the page for the necessary technology
Use Namespaces
Setup the location to the database
Create a Connection String
Create a Command Object (SQL)
The work required from the database
Open the connection, Execute the Command, Create a Reader
Execute!
Loop through the Reader and read the data
csFees
myCommand
GUI controls allow us to do a great deal but they can’t do everything
.NET provides a number of objects that allow us to perform database manipulation in code
The database objects are collected into three Namespaces
A namespace is a way to uniquely identify a set of programming objects
"1",“Registration Fee",5.00, ”2”, “Vehicle License Fee",7.50, ”3”, “Weight Fee“, 12.50

6. A. Get ready with Namespaces
Namespaces are libraries of database functions
Needed while working with database in code
“Using” suggests that these functions be loaded
The following must be added at the top of the .cs file

7. B.1 Connection – What is it?
Called a Connection String (e.g. csFees)
Stored in the web.config file
Includes path and name to the database
Is created automatically when an sds is configured

8. B.2 Connection – create in 3 steps
Using its name from the web.config file
And can be pulled into your code with the ConfigurationManager
Create a connection string object in your “.cs” page
Finally, create the Connection Object
These two should match
Also used with sds In Design View

9. C.1 Command Object – What is it?
Equivalent to the GUI SQL Data Source
Contains SQL, database driver, path, and name
SQL commands: SELECT, INSERT, UPDATE, DELETE
Two types:
SELECT commands make DataReaders, and return data
All other commends modify the data
So they use ExecuteNonQuery & return a number

10. C.2 Command object – creating it
Tells the database what to do
Is created with an SQL string & the connection object
The Connection Object was made in the previous slide

11. D. Executing the Command - sequence
Open the connection
Execute the command, create the reader
Loop through the Reader
AFTER the looping code, Close the connection
// See next slide for looping code
"1",“Registration Fee",5.00, ”2”, “Vehicle License Fee",7.50, ”3”, “Weight Fee“, 12.50

12. E. Parsing through the Reader
Review the SELECT statement
Retrieve the records if there are any
“.Read()” returns TRUE if there is a record
FALSE if no records are found
Address columns by index or field name
Data type is always string
There are several ways to process the RecordSet but the simplest is probably to use a DataReader
Returns one record at a time to the program when the .Read() method is called
Read() returns a value of false if there are no (more) records to read, true if there was a record
Can be used to control a loop
“Registration Fee",5.00, “Vehicle License Fee",7.50, “Weight Fee“, 12.50
lblFees.Text += "<br />" + strDescription + " " + decFee.ToString("c2");

13. F. Closing the Connection
Technically known as Garbage Collection
Done to free up database server memory
Critical step, causes Denial of Service on server
myReader.Close(); myConnection.Close();

14. Parameters, a safety measure
Are a security measure
Are placeholders of a values within SQL
Values need to supplied before execution
Adding a parameter to a command. The first argument is the name of the parameter, the second argument is the datatype (when you type System.Data.SqlDbType. you will see a list of all the SQL datatypes and can pick the appropriate one.
2. Parameter is given a value
3. Matches the SQL data type in the database
1. Parameter appears

15. L1: Hands on
Purpose:
To read and display all the records in a database
then read and display selected records
Start a new page
yourlastnameU9L1 in the Unit9 folder.
Add heading, heading size
Reading Fee Data Using Code
Add a Button to the page
Button ID, button text
Add a Label to hold the results displayed
Label ID, text

16. U9L1 - 2
Write code that needs to be executed for the button. Use the five step plan:
Import namespaces (Step A)
Create the connection (Steps B.2.2 & B.2.3)
Create an SqlCommand object (Step C)
Execute the command object (Step D)

17. U9L1 - 3 Read the data record in a loop (Step E)
Copy the Description data from field 0 to a string variable
Convert the Fee data from field 1 and store it in a decimal variable
Accumulate the descriptions and fees in lblFees (without deleting previous entries)
After the loop finishes, Close the Reader and the Connection (Step F)
Add a try/catch block to the page
Inside the try, put the risky code
Inside the catch, display an appropriate error message

18. U9L1 - 4
Test your page, you should show fee descriptions and fee amounts, as shown on the right.
Once that part works correctly skip a line after your label and type the words “Enter a test value:”, followed by a TextBox
Set the (ID) of the TextBox to txtTest
Validate for a positive decimal value

19. U9L1 - 5 Add a button on the line below the TextBox
Set the (ID) to btnTest2
Set the Text to “Display fees greater than or equal to the test value”
Double click the button to start creating the method
Copy all the code from the btnReadFees_Click method and paste it in the new method
Locate the SQL statement and change it to say
SELECT [FeeDescription], [Fee] FROM Fees WHERE [Fee]

20. U9L1 - 6
Add a new line of code after the line where you create the sqlCommand
Get the test value from the TextBox
And create a parameter with it (See slide on adding Parameters)
decimal decTest = Convert.ToDecimal(txtTest.Text);
System.Data.SqlDbType.Money).Value = decTest;

21. U9L1 - 7
Test your page and check the results. You should get something like this (depending on what data you have in your database)
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