关于数据库连接串中的DataDirectory的官方说明-优快云博客

本文介绍了一种简化数据库文件路径配置的方法——DataDirectory宏。通过使用此宏，可以避免将完整的数据库路径硬编码到连接字符串中，从而使得项目更易于分享和部署。.NET运行时支持在多种应用环境下自动扩展此宏，如桌面应用程序、ClickOnce发布的应用程序及Web应用。

Full path vs relative path

One of the reasons why it was hard to work with database files before is that the full path to the database was serialized in different places. This made it harder to share a project and also to deploy the application. In this version, the .NET runtime added support for what we call the DataDirectory macro. This allows Visual Studio to put a special variable in the connection string that will be expanded at run-time. So instead of having a connection string like this:

      "Data Source=.\SQLExpress;AttachDbFileName=c:\program files\app\data.mdf"

You can have a connection string like this:

      "Data Source=.\SQLExpress;AttachDbFileName=|DataDirectory|\data.mdf"

This connection string syntax is supported by the SqlClient and OleDb managed providers.

By default, the |DataDirectory| variable will be expanded as follow:

      - For applications placed in a directory on the user machine, this will be the app's (.exe) folder.
      - For apps running under ClickOnce, this will be a special data folder created by ClickOnce
      - For Web apps, this will be the App_Data folder

Under the hood, the value for |DataDirectory| simply comes from a property on the app domain. It is possible to change that value and override the default behavior by doing this:

      AppDomain.CurrentDomain.SetData("DataDirectory", newpath)

https://blogs.msdn.microsoft.com/smartclientdata/2005/08/26/working-with-local-databases/

转载于:https://www.cnblogs.com/woolhoo/p/8683094.html