怎么把App.config中的连接数据库的代码改为应用SqlConnection连接数据库

这是App.config中连接数据库的代码

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <connectionStrings>
    <add name="sqlserver" connectionString="Server=127.0.0.1;Initial Catalog=Hotel;User ID=sa;Password=1234" providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration>

怎么改成下面这样

string connstring = "Server=.; user Id = sa; Pwd = 1234; DataBase = Library";//Data Source =172.20.10.5;Initial Catalog = Library;User ID= sa;Pwd=1234
            SqlConnection conn = new SqlConnection(connstring);
            string sql = String.Format("select count(*) from [Manager] where managerid='{0}' and managerPassword='{1}' and mIdentity='{2}'", username, passworld,midentity );

string connstring = System.Configuration.ConfigurationManager.ConnectionStrings["sqlserver"].ConnectionString;

如果只是改成代码形式，不从配置文件里面读取，可以把app.config里面的 添加连接数据库的那部分去掉，再通用类下面这连接数据库代码