Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 4 ■ DATA BINDING WITH ASP.NET 87
of a table in your database. Executing this type of command will return all records stored
in that table.
So, for example, if you want to create a query that returns the street address for customers
in the AdventureWorks address database who live at postal code 98011, you
would use code like this:
string connectionString =
WebConfigurationManager.ConnectionStrings["AW"].ConnectionString;
SqlConnection sqlCon = new SqlConnection(connectionString);
SqlCommand sqlComm = new SqlCommand();
sqlComm.Connection = sqlCon;
sqlComm.CommandType = CommandType.Text;
sqlComm.CommandText =
"SELECT AddressLine1 FROM Person.Address " +
"WHERE (PostalCode = N'98011')";
Executing the Command
Now that you have your command, you are going to want to execute it to do anything
meaningful. There are four different methods for executing an ADO.NET command:
ExecuteNonQuery: This is used to execute a query for which you do not want to return
a result set. For example, if you are inserting, updating, or deleting records, you can
use the command’s ExecuteNonQuery method. It will return an integer containing the
number of records that were affected.
ExecuteScalar: This executes the query and returns the first column of the first row
of the result set. This is very useful for queries that use SQL COUNT or SUM, or other
queries that return a desirable value.
ExecuteReader: This executes a SELECT query and returns a DataReader object that can
be used to provide forward-only read access to your data.
ExecuteXmlReader: This is similar to ExecuteReader except that it gives you an XmlReader
to access the data.
So, executing a command to generate the required feedback is very straightforward.
Here’s an example of executing the previous query, with the results available via a
SqlDataReader:
SqlDataReader sRead = sqlComm.ExecuteReader();