The SqlCommand class in the .NET Framework Data Provider has four methods that you can use to execute SQL
- ExecuteScalar: Executes a query that returns a single scalar value.
- ExecuteReader: Executes a query that returns a result set.
- ExecuteNonQuery: Executes a data update statements or a catalog update statement.
- ExecuteXmlReader: Executes a query that returns an Extensible Markup Language (XML) result set, this method is only avaliable in the SqlCommand class.
To execute a simple database query
- Import the System.Configuration namespace
- Use the ConfigurationManager.ConnectionStrings property to get a collection of connection strings from the application configuration file.
- Index into the collection of connection strings by using the programmatic name of the connection string you want to access.
- Use the ConnectionString property to get the connection string information.
- Create a connection object.
- Create a command object.
If you want to execute an SQL statement, set the CommandType property of the command object to the
CommandType.Text enumeration value. If you want to call a stored procedure, set the CommandType property of the command
object to the CommandType.StoredProcedure enumeration value.
- Call the Open method on the connection object.
- Call the ExecuteScalar method on the command object. Assign the result to a suitably typed variable.
- Call the Close method on the connection object.
The following example shows how to execute a query to determine the number of products in the AdventureWorks2016CTP3 database
on the local SQL Server instance.