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C# SqlCommand Example: SELECT TOP, ORDER BYUse SqlCommand from System.Data.SqlClient. Specify SELECT TOP, ORDER BY statements.
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SqlCommand. This type deals with databases. It executes SQL commands on a database. It sends an SQL command to a database that is specified by an SqlConnection object.

We then call instance methods to physically apply the command to the database. We use a SELECT TOP command text, and also ORDER BY.

Example. This program uses the SqlCommand data object in C#. We use SqlCommand in the context of a complete but trivial program that reads data from a specific database on the disk.

Info The SqlCommand type has a public parameterized constructor and it can be used with one or more arguments.

And The first parameter specifies the SQL statement. The second parameter is the SqlConnection. The third parameter is the SqlTransaction.

Important This program interfaces with the SQL Server engine. It uses some project-specific external data.

SqlClient

SqlDataReader

So It will not work for you unless you change the connection string reference and the SQL command text for your environment.

C# program that uses SqlCommand instance
using System; using System.Data.SqlClient; class Program { static void Main() { // // The program accesses the connection string. // ... It uses it on a connection. // string conString = ConsoleApplication1.Properties.Settings.Default.ConnectionString; using (SqlConnection connection = new SqlConnection(conString)) { connection.Open(); // // SqlCommand should be created inside using. // ... It receives the SQL statement. // ... It receives the connection object. // ... The SQL text works with a specific database. // using (SqlCommand command = new SqlCommand( "SELECT TOP 3 * FROM Dogs1 ORDER BY Weight", connection)) { // // Instance methods can be used on the SqlCommand. // ... These read data. // using (SqlDataReader reader = command.ExecuteReader()) { while (reader.Read()) { for (int i = 0; i < reader.FieldCount; i++) { Console.WriteLine(reader.GetValue(i)); } Console.WriteLine(); } } } } } }
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Using. The SQL data objects are wrapped in a resource acquisition statement. This ensures that resources are properly acquired and disposed of when no longer needed.

Using

Constructor. The call to the SqlCommand constructor uses 2 parameters. The first parameter is the actual SQL source text. This string uses SQL and is not compiled by the C# compiler.

And The second parameter is the SqlConnection object. This is set up elsewhere in the program.

Overview You must manually specify the connection to use on the SqlCommand. This can be done with a parameter on the constructor.

A summary. We wrote a complete program that reads from a database on the local disk. The SqlCommand has a constructor. You can specify its connection and the SQL text.

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