C#中配置文件的问题

配置文件-------------------------------------------------------------------
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
  <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
   <section name="MyForm.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </sectionGroup>
 </configSections>
 <appSettings>
</appSettings>
<connectionStrings>
<add name="MySqlConnectionString" connectionString="Data Source=127.0.0.1;uid=sa;pwd=sasa;database=Student" providerName="System.Data.SqlClient"/>
</connectionStrings> <applicationSettings>
  <MyForm.Properties.Settings>
   <setting name="MyForm_localhost_WebService" serializeAs="String">
    <value>http://localhost/MyWebservice/Webservice/WebService.asmx</value>
   </setting>
  </MyForm.Properties.Settings>
 </applicationSettings>
</configuration>
调用的代码
-----------------------------------------------------------------------------
using System;
using System.Data;
using System.Configuration;
using System.Collections.Generic;
using System.Text;using System.Data.Common;
using System.Data.SqlClient;
namespace MyForm.DBLibrary
{
    class DBBase
    {
  public bool Query(string Str_SQL, ref DataTable Dtb_Result)
        {
            CreatConnection();
            DbCommand dbCommand = dbProvider.CreateCommand();
            dbCommand.CommandType = CommandType.Text;
            dbCommand.CommandText = Str_SQL;
            dbCommand.Connection = dbConnection;            DbDataAdapter ad = dbProvider.CreateDataAdapter();
            ad.SelectCommand = dbCommand;            dbConnection.Open();            try
            {
                ad.Fill(Dtb_Result);
                dbConnection.Close();
                return true;
            }
            catch (Exception ex)
            {
                dbConnection.Close();
                return false;
            }
        }
    }
}
这个怎么得到数据库连接的呀？
用 CreatConnection();就可以么？
我以前是这样写的connection con=new connection(server=.;database=student;uid=sa;pwd=sasa);
请大家帮解释我一下，
配置文件怎么怎么用的？请大家帮我解释一下上面的代码
主要是配置文件
谢谢大家了