连接字符串:

server=潘尚\\SQLEXPRESS;database=db_test;Trusted_Connection=true

连接代码:

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SQLTest
{
    class Program
    {
        static void Main(string[] args)
        {
            //连接数据库
            string connection =
                "server=潘尚\\SQLEXPRESS;database=db_test;Trusted_Connection=true";
            SqlConnection sc = new SqlConnection();
            sc.ConnectionString = connection;
            try
            {
                sc.Open();
                Console.WriteLine("已经打开数据库连接!");
            }
            catch (Exception ex)
            {
                Console.WriteLine("打开数据库错误:{0}", ex.Message);
            }
            finally
            {
                sc.Close();
                Console.WriteLine("数据库连接已关闭!");
            }
            System.Console.ReadLine();
        }
    }
}

连接结果: