C# 連接oralce sqlserver mysql 連接方式

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
    </startup>
  <connectionStrings>
    <!--oracle數據庫連接-->
    <add name="ConnOrcle" connectionString="server=.;database=demo;uid=sa;pwd=123456" providerName="System.Data.SqlClient"/>
    <!--SQLServer數據庫連接-->
    <add name="ConnSQLServer" connectionString="Provider=MSDAORA;Data Source=demo;User ID=sa;Password=123456;" providerName="System.Data.OracleClient"/>
    <!--mysql數據庫連接-->
    <add name="Conn" connectionString="host=127.0.0.1;Port=3306;Database=mysql;uid=sa;pwd=12346" providerName="MySql.Data.MySqlClient"/>
  </connectionStrings>
</configuration>