管道符变量在连接字符串中有什么作用？

Question

我知道在ASP.NET应用程序中，|DataDirectory|会解析为App_Data，但这是硬编码的吗？还是有一种类似于%环境变量%的通用机制在起作用？

- marxidad

Answer 1

来自 MSDN Smart Client Data Blog：

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...

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)

- Yaakov Ellis