如何在运行时动态构建SQL连接字符串？

I'm uploading the .mdf files at runtime to the application and when i upload a file i create a SQL connection string when the upload finish so i can save it to my database, then i'm trying to connect to the mdf file that i've uploaded before but i have many error (depending on the connection string that i try).I'm uploading the .mdf files at runtime to the