A column ID occurred more than once in the specification?

问题

I am getting this error message when using EF 4.1 code first approach with Sql compact 4. I don't see any model who has id column more than one so i have no idea why this error occured. What can cause this error ?

Edit : I want to specifiy few extra things. Database creating is success but model creating is not. And Exception has been thrown from sqlce methods.

回答1:

This issue stems from a SQL query that returns two or more columns that have an identical name. SQL will handle exact duplicate names on columns with no problem but c# will puke errors all over like this one.

example situation:

TableA
  int Id
  varchar Name

TableB
  int Id
  int A_Id
  varchar Name


SELECT A.*,
       B.Name
FROM TableA A

INNER JOIN TableB 
   ON B.A_Id = A.Id

The Id and Name columns would be duplicated and cause an exception with EF

回答2:

This could also be caused when the migration code is not update to date. This usally occurs when the executing the Add-Mirgration muliple times. Run the following command instead:

Add-Migration <migration-name> -force

来源：https://stackoverflow.com/questions/5750742/a-column-id-occurred-more-than-once-in-the-specification