Create and Execute On-the-Fly Batch Updates by Using ADO.NET

4.4 Create and Execute On-the-Fly Batch Updates by Using ADO.NET Sometimes in database applications, you want to create and execute stored procedures that don't currently exist.. When yo

4.4 Create and Execute On-the-Fly Batch Updates by Using ADO.NET

Sometimes in database applications, you want to create and execute stored procedures that don't currently exist When you have a situation in which you need to use highly dynamic stored procedures that might use criteria that is entirely created at runtime, you might need to create those stored procedures on-the-fly This How-To shows you how to create and execute these stored procedures

It's great that you can execute stored procedures that are already created, but what if you need to generate one at runtime? How do you do this?

Technique

To perform this How-To, you will be utilizing the OleDBCommand object, and feeding

in the CommandText property from a text box The text box is set to "Update Employees Set City = 'Redmond' Where City = 'Seattle'" to give you something to start with

Steps

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

command button with the caption How-To 4.4 When the form loads, you will see an example update statement in a text box Click on the Execute button to execute the update statement A TextBox control is then displayed on the bottom of the form showing the number of records that are affected You can the form in Figure 4.3

Figure 4.3 This form uses the Command object with a SQL statement passed to

execute the specified action

Note

The number of records affected might be different on your system depending on what you have been doing with the Northwind data

1 Create a new Windows Form

2 Add the following controls, setting the properties as listed in Table 4.6

Table 4.6 Controls Property Settings Object Property Setting

Label Name

Caption

Label1 Update Statement to Execute:

Button Name btnExecute

TextBox Name

Text

txtSQL Update Employees Set City = 'Redmond' Where City = 'Seattle'

MultiLine True

Label Name

Caption

Label2 Records Affected:

TextBox Name txtRecsAffected

3 Enter the following code to the Click event btnExecute When the command is instantiated in this case, the string in the txtSQL text box is passed as the

CommandText The CommandType is set as CommandType.Text The connection

is then open Finally, the command is executed with the ExecuteNonQuery

method, with the ToString passing back the number of records that were affected

to the Text property of the txtRecsAffected text box

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

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

6

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

"Northwind"))

8 Dim ocmdPhoneUp As New OleDb.OleDbCommand(Me.txtSQL.Text, ocnn)

9

10 Try

11 ' Specify the name of the stored procedure

12 ocmdPhoneUp.CommandType = CommandType.Text

13

14 ' Open the connection object

15 ocnn.Open()

16

17 Me.txtRecsAffected.Text = ocmdPhoneUp.ExecuteNonQuery.ToString

18

19 Catch excpData As Exception

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

21

22 End Try

23 End Sub

Tip

Use a Try…Catch…End Try block to trap any exceptions that might occur when working with ADO.NET In this case, the error is trapped and a message box displays the error Remember that exceptions that are not trapped will cause the application to fail

How It Works

When a valid SQL statement is entered into the text box with the label Update Statement

to Execute: and the Execute button is clicked, the command entered is executed, and the number of records that were affected is returned

Comments

The Command object is a real workhorse when it comes to performing bulk operations, whether working with store procedures already created or when using statements that have been created on-the-fly