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Working with connection strings programmatically can be cumbersome because they are often represented as string literals, which are difficult to maintain and error-prone at best. The Microsoftsupplied ADO.NET data providers support connection string builder objects, which allow you to establish the name/value pairs using strongly typed properties. Consider the following update to the current Main() method:

Numerical data types are used for storing numbers and include the integer, serial, float, and numeric types.

static void Main(string[] args) { Console.WriteLine("***** Fun with Data Readers *****\n"); // Create a connection string via the builder object. SqlConnectionStringBuilder cnStrBuilder = new SqlConnectionStringBuilder(); cnStrBuilder.InitialCatalog = "AutoLot"; cnStrBuilder.DataSource = @"(local)\SQLEXPRESS"; cnStrBuilder.ConnectTimeout = 30; cnStrBuilder.IntegratedSecurity = true; using(SqlConnection cn = new SqlConnection()) { cn.ConnectionString = cnStrBuilder.ConnectionString; cn.Open(); ShowConnectionStatus(cn); ... } Console.ReadLine(); } In this iteration, you create an instance of SqlConnectionStringBuilder, set the properties accordingly, and obtain the internal string using the ConnectionString property. Also note that you use the default constructor of the type. If you so choose, you can also create an instance of your data provider s connection string builder object by passing in an existing connection string as a starting point (this can be helpful when you read these values dynamically from an App.config file). Once you have hydrated the object with the initial string data, you can change specific name/value pairs using the related properties, as in this example: static void Main(string[] args) { Console.WriteLine("***** Fun with Data Readers *****\n"); // Assume you really obtained the cnStr value from a *.config file. string cnStr = @"Data Source=(local)\SQLEXPRESS;" + "Integrated Security=SSPI;Initial Catalog=AutoLot"; SqlConnectionStringBuilder cnStrBuilder = new SqlConnectionStringBuilder(cnStr); // Change timeout value. cnStrBuilder.ConnectTimeout = 5; ... }

Now that you understand better the role of the connection object, the next order of business is to check out how to submit SQL queries to the database in question. The SqlCommand type (which derives from DbCommand) is an OO representation of a SQL query, table name, or stored procedure. You specify the type of command using the CommandType property, which can take any value from the CommandType enum: public enum CommandType { StoredProcedure, TableDirect, Text // Default value. } When you create a command object, you can establish the SQL query as a constructor parameter or directly by using the CommandText property. Also when you create a command object, you need to specify the connection you want to use. Again, you can do so as a constructor parameter or by using the Connection property. Consider this code snippet: // Create command object via ctor args. string strSQL = "Select * From Inventory"; SqlCommand myCommand = new SqlCommand(strSQL, cn); // Create another command object via properties. SqlCommand testCommand = new SqlCommand(); testCommand.Connection = cn; testCommand.CommandText = strSQL; Realize that at this point that you have not literally submitted the SQL query to the AutoLot database, but instead prepared the state of the command object for future use. Table 21-6 highlights some additional members of the DbCommand type. Table 21-6. Members of the DbCommand Type

This field type is used for storing integers, such as node IDs. If the unsigned key is TRUE, negative integers will not be allowed. $field['fieldname'] = array( 'type' => 'int', // Required. 'unsigned' => TRUE, // Defaults to FALSE. 'size' => 'small', // tiny | small | medium | normal | big 'not null' => TRUE, // Defaults to FALSE. 'description' => t('Always state the purpose of your field.'), );

Gets or sets the time to wait while executing the command before terminating the attempt and generating an error. The default is 30 seconds. Gets or sets the DbConnection used by this instance of the DbCommand. Gets the collection of DbParameter objects used for a parameterized query. Cancels the execution of a command. Executes a SQL query and returns the data provider s DbDataReader object, which provides forward-only, read-only access for the result of the query.

Connection Parameters Cancel() ExecuteReader()