C # Connect to SQL Server

Connection connection class

Use the SqlConNetion class. When using the SQLConnection class, you want to reference a namespace of system.data.sqlclient.

using System.Data.SqlClient;

CommandCommand class

Using the SQLCommand database command class mainly performs operations for the database, such as inserting, deleting, modifying the database.

DataReader read class

Use SqlDataReader. Database read category is the database command class in the data type of the result returned after the query operation. Database read category is only available when the database's connection status is in an open state. When the database is closed, the database read category is no longer valid.

DataSet Class

The data set is equivalent to a virtual database, and each data set includes multiple data sheets. Even if the database is connected, it is still possible to continue access to the record from the data set, but the data is stored in the data set and is not stored in the database.

DataAdapter adaptation class

You can use SqlDataAdapter. The data adapter is often used with the data set. The data adapter can store the data in the database to the data set, and the data adapter can be said to be a bridge between the data set and the database.

Connect to the database

Enter your own server name here, there are two login methods, Windows and authentication logins. This is the same way as you create a database.

Again to choose the table you need to operate here.

There are two ways to connect the database(See how you log in)

Data Source = server name; Initial catalog = database name; user ID = username; PWD = password (no password can be omitted)

Column:

string connStr = "Data Source=.;Initial Catalog = MySchool;User ID = aa;Password=123";  

 string connStr = "Data Source=.;Initial Catalog=QQ;Integrated Security=True";

Here we can directly view the code for connecting the database.

Next, you can operate the database.

The test is successful

 public void TestConSQL()
        { 
        // Test connection database
            string connStr = "Data Source=.;Initial Catalog=QQ2021;Integrated Security=True";
            SqlConnection conn = new SqlConnection(connStr);
            // Open the database
            conn.Open();
            Console.WriteLine("Open Database Connection");
            // Close the database
            conn.Close();
            Console.WriteLine("Close Database Connection");
        }