Using a DataReader Object in Visual Studio .NET

Using a DataReader Object in Visual Studio .NET You can't visually create a DataReader object in Visual Studio .NET VS .NET; you can only create them using program statements.. In this s

Using a DataReader Object in Visual Studio NET

You can't visually create a DataReader object in Visual Studio NET (VS NET); you can only create them using program statements

In this section, you'll see how to create a SqlDataReader object and use it to retrieve the result set from a SqlCommand object, which you saw how to create using VS NET in the

the CustomerID, CompanyName, and ContactName columns from the Customers table You'll see how to execute this SELECT statement, read the result set using the

SqlDataReader object, and display the result set in a ListView control A ListView

control allows you to view information laid out in a grid

Note You can either modify the MyDataReader project you created in the previous

you can simply open the completed VS NET project contained in the DataReader

directory To open the completed project, select File ➣ Open ➣ Project, browse to

the VS NET projects\DataReader directory, and open the

WindowsApplication4.csproj file

If you are modifying your existing Windows application, drag a ListView control to your form Figure 9.2 shows a form with a ListView control Make sure the Name property of your ListView is set to listView1 (this is the default name, so you shouldn't have to

change it)

Figure 9.2: Adding a ListView control to the form

Warning If you opened the completed project, you don't have to add a ListView controI;

it's already on the completed form You will need to change the

ConnectionString property of the sqlConnection1 object so that it connects to

your SQL Server Northwind database Once you've set your ConnectionString,

you can run the form by selecting Debug ➣ Start Without Debugging

Next, double-click an area on your form outside the ListView control This causes VS .NET to display the code editor, and you'll see the cursor positioned in the Form1_Load() method; this method is called when your form is initially loaded at runtime Typically, this is the method by which you want to execute your database operations Set your Form1_Load() method to the following code:

private void Form1_Load(object sender, System.EventArgs e)

{

sqlConnection1.Open();

System.Data.SqlClient.SqlDataReader mySqlDataReader =

sqlCommand1.ExecuteReader();

while (mySqlDataReader.Read())

{

listView1.Items.Add(mySqlDataReader["CustomerID"].ToString());

listView1.Items.Add(mySqlDataReader["CompanyName"].ToString());

listView1.Items.Add(mySqlDataReader["ContactName"].ToString());

}

mySqlDataReader.Close();

sqlConnection1.Close();

}

Notice you add an item to the ListView control using the Add() method, which is

accessed using the Items property The Add() method expects a string parameter, and you therefore call the ToString() method to convert the object returned by the SqlDataReader object to a string Also notice you include the namespace when referencing the

SqlDataReader class: you use System.Data.SqlClient SqlDataReader when creating the SqlDataReader object

The previous code opens the database connection, creates a SqlDataReader object, and uses it to read the rows from the result set returned by the SqlCommand object Each column of the result set is then added to the ListView control using the Add() method

Figure 9.3: The completed Form1_Load() method

Before you run your form, you'll need to add a substring containing the password for the database connection to the ConnectString property of your SqlConnection object For my installation of SQL Server, the password to access the Northwind database is sa, and my ConnectionString property is set to:

data source=localhost;initial catalog=Northwind;persist security info=False;user

id=sa;pwd=sa;workstation id=JMPRICE-DT1;packet size=4096

Notice the substring pwd=sa in this string to set the password

Finally, run your form by pressing Ctl+F5 on your keyboard, or select Debug â Start Without Debugging Figure 9.4 shows the running form

Figure 9.4: The running form

Save your MyDataReader project by selecting File ➣ Save All You'll use this project in later chapters If you used the completed DataReader project rather than modifying your existing project, don't worry: you'll be able to use the completed DataReader project in the later chapters also