c# sqlconnection

using System;
using System.Data.SqlClient;

class Program
{
    static void Main()
    {
        // 定义连接字符串，包含数据库服务器地址、数据库名称、认证方式等信息
        string connectionString = "Server=myServerAddress;Database=myDataBase;User Id=myUsername;Password=myPassword;";

        // 创建SqlConnection对象，并传入连接字符串
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            try
            {
                // 打开数据库连接
                connection.Open();
                Console.WriteLine("Connection opened successfully.");

                // 执行SQL查询
                string query = "SELECT * FROM myTable";
                using (SqlCommand command = new SqlCommand(query, connection))
                {
                    using (SqlDataReader reader = command.ExecuteReader())
                    {
                        // 读取查询结果
                        while (reader.Read())
                        {
                            Console.WriteLine(reader["columnName"].ToString());
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                // 捕获并处理异常
                Console.WriteLine("An error occurred: " + ex.Message);
            }
            finally
            {
                // 确保连接关闭
                if (connection.State == System.Data.ConnectionState.Open)
                {
                    connection.Close();
                    Console.WriteLine("Connection closed.");
                }
            }
        }
    }
}

这段代码展示了如何使用C#中的SqlConnection类来连接到SQL Server数据库。它包括了定义连接字符串、创建SqlConnection对象、打开连接、执行SQL查询以及处理异常的完整流程。