标准连接:
string str="Server=myServerAddress;Database=myDataBase;User Id=myUsername;Password=myPassword;";
信任连接:
string str="Server=myServerAddress;Database=myDataBase;Trusted_Connection=True;";
连接服务器某个实例
string str="Server=myServerName\myInstanceName;Database=myDataBase;
User Id=myUsername;Password=myPassword;";