Tài liệu Execute Parameterized Stored Procedures in ADO.NET ppt

4.3 Execute Parameterized Stored Procedures in ADO.NET To take advantage of stored procedures to their full power, you need to be able to pass parameters so that specific criteria can be

4.3 Execute Parameterized Stored Procedures in ADO.NET

To take advantage of stored procedures to their full power, you need to be able to pass parameters so that specific criteria can be used This How-To describes how to create parameters off the OleDbCommand objects to pass parameters to SQL Server

You need to execute a parameterized stored procedure in your application How do you

do this using Visual Basic NET and ADO.NET?

Technique

In ADO, you have a Command object to execute stored procedures, among other tasks In ADO.NET, you also have a Command object that performs basically the same task In fact, many of the properties and methods that you use are the same You can see a list of those in Table 4.4

Table 4.4 Objects That Are Used for This Technique, with Properties and Methods Object Property Description/Method

Connection ConnectionString Contains the connection string that is used

Connection Open Opens the connection that the Command object uses Command cmdText Specifies the SQL statement to use Can be SQL

statement or names of objects such as tables or stored procedures

Command Connection Uses the Connection object

Command CommandType Specifies the type of command you want to execute

Can be one of the following command types:

StoredProcedure, DirectTable, or Text

Command Parameters Parameters to pass to the stored procedure

Command ExecuteReader Creates a DataReader object with the data that the

command object specifies

DataReader Read Reads the next record in the DataReader, and also tests

the end of the data returned

DataReader GetString Returns the current record, getting the column

specified, and returns it as string

DataReader GetInt32 Returns the current record, getting the column

specified, and returns it as 32-bit integer

You will use these objects and their properties and methods for the following steps

Steps

Open and run the VB.NET-Chapter 4 solution From the main form, click on the

command button with the caption How-To 4.3 When the form loads, click on the View button to display the orders for the customer ID that is specified By default, this is ALKI A TextBox control is then displayed on the bottom of the form You can see the form in Figure 4.2

1 Create a new Windows Form

2 Add the following controls, setting the properties as listed in Table 4.5

Table 4.5 Controls Property Settings Object Property Setting

Label Name

Caption

Label1 Products and Quantities Ordered By:

TextBox Name

Text

txtCustID ALFKI Button Name

Text

btnView

&View TextBox Name

MultiLine

txtResults True

3 Enter the following code to the Click event btnView This code takes the

connection and creates the command object The name of the stored procedure is passed, and the command type is specified, which is

CommandType.StoredProcedure Next, parameters and the DataReader are

created The last task is to iterate through the data and add it to the display text box

4 Private Sub btnView_Click(ByVal sender As System.Object, _

5 ByVal e As System.EventArgs) Handles btnView.Click

6

7 Dim ocnn As New OleDb.OleDbConnection(BuildCnnStr("(local)",

8 "Northwind"))

9 Dim ocmdCustHist As New OleDb.OleDbCommand("CustOrderHist", ocnn)

10 Dim odrCustHist As OleDb.OleDbDataReader

11

12 Try

13 ' Specify the name of the stored procedure

14 ocmdCustHist.CommandType = CommandType.StoredProcedure

15

16 ' Specify the parameters

17 ocmdCustHist.Parameters.Add("@CustomerID", Me.txtCustID.Text)

18

19 ' Open the connection object

20 ocnn.Open()

21

22 ' Establish the DataRead object

23 odrCustHist = _

24 ocmdCustHist.ExecuteReader(CommandBehavior.SequentialAccess)

25

26 ' Iterate through the data loaded, building the results string

27 Do While odrCustHist.Read

28 Me.txtResults.Text &= odrCustHist.GetString(0) & _

29 ", " & odrCustHist.GetInt32(1) & vbCrLf

30 Loop

31

32 Catch excpData As Exception

33 MessageBox.Show("Error Occurred: " & excpData.Message)

34

35 End Try

36 End Sub

Figure 4.2 This form uses the Command object with a stored procedure to populate

the TextBox control

How It Works

When the user clicks on the View button with Customer ID filled in, the text box below is filled in, displaying order information for that customer

Comments

Using the technique presented here, you can pretty well perform the majority of the tasks you need to by using Command objects and stored procedures