Tài liệu Creating a Command Object Using Visual Studio .NET docx

Creating a Command Object Using Visual Studio .NET To create a SqlCommand object using Visual Studio .NET VS .NET, you drag a SqlCommand object from the Data tab of the Toolbox to your f

Creating a Command Object Using Visual Studio NET

To create a SqlCommand object using Visual Studio NET (VS NET), you drag a

SqlCommand object from the Data tab of the Toolbox to your form You can also drag an OleDbCommand object from the Data tab of the Toolbox to your form

Before you perform the procedure explained in this section, do the following:

1 Create a new project named MyDataReader containing a Windows application

see how to add a SqlConnection object using VS NET) This object will have the default name of sqlConnection1

3 Configure your sqlConnection1 object to access your Northwind database

object This object is assigned the default name of sqlCommand1

Figure 8.1: A SqlCommand object in a form

You then set the Connection property for your sqlCommand1 using the drop-down list to the right of the Connection property in the Properties window You can select an existing Connection object from the drop-down list; you can also create a new Connection object

by selecting New from the list For this example, select your existing sqlConnection1

You can use Query Builder to create a SQL statement by clicking on the ellipsis button to the right of the CommandText property, and you can set parameters for a command by clicking the ellipsis button to the right of the Parameters property You'll set the

CommandText property of your SqlCommand object to a SELECT statement that

retrieves the CustomerID, CompanyName, and ContactName columns from the

Customers table You'll construct this SELECT statement using Query Builder To get started, click the ellipsis button to the right of the CommandText property for your

SqlCommand object

Add button to add the Customers table to your query Click the Close button to continue

Figure 8.2: Adding the Customers table to the query using the Add Table dialog

Next, you construct your query using Query Builder You select the columns you want to retrieve here Add the CustomerID, CompanyName, and ContactName columns using

Figure 8.3: Adding the CustomerID, CompanyName, and ContactName columns to the query using Query Builder

Click the OK button to continue The CommandText property of your SqlCommand object is then set to the SELECT statement you created in Query Builder

Note Save your MyDataReader project by selecting File ➣ Save All You'll see the use