问题
I'm pretty sure that the .accde file does exist. I noticed that VS asks for .mdb file, but a .accde is also a MS Access generated database file.
Here is the screenshot(hope it helps):

回答1:
From the MSDN AccessDataSource page.
The AccessDataSource class does not support connecting to Access databases that are protected by a user name or password, because you cannot set the ConnectionString property. If your Access database is protected by a user name or password, use the
SqlDataSource
control to connect to it so that you can specify a complete connection string.
So the .accde is protected in terms of security. Try use SqlDataSource
.
来源:https://stackoverflow.com/questions/7550272/cant-add-a-accde-ms-access-filelocated-outside-the-project-folder-as-accessd