// windows验证方式
string connectionStringTest = @"Data Source=ADMINISTRATOR\SQLEXPRESS;Initial Catalog=TestDB;Integrated Security=SSPI; ";

//建立信任连接（具体含义与同其他方式的区别还需学习）
string connectionStringTest = @"server=ADMINISTRATOR\SQLEXPRESS;Initial Catalog=TestDB;Integrated Security=True";

//网站连接数据库的标准方式
string connectionStringTest = @"server=ADMINISTRATOR\SQLEXPRESS;database=TestDB;user id=testuser;password=123456";

//应用程序连接数据库的标准方式
string connectionStringTest = @"Data Source = ADMINISTRATOR\SQLEXPRESS; Initial Catalog = TestDB; User Id = testuser; Password = 123456;";

SqlConnection conn = new SqlConnection(connectionStringTest);
try
{     
      conn.Open();
      MessageBox.Show("数据库链接成功！","提示");
}
catch (Exception e)
{
         string message = e.Message;
}
finally
{
       conn.Close();
       conn.Dispose();
}