login failed connecting to SQL Server with AttachDbFilename and User Instance

I am developing ASP.NET 2.0 application using SQL Express 2005. I have attached my database with the application.

The Connection string:

 <add name="WCMIRConnectionString"  providerName=开发者_如何学JAVA"System.Data.SqlClient"
  connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=&quot;\App_Data\WCMIR.mdf&quot;;Integrated Security=True;Trusted_Connection=no;User Instance=True" />

When trying to connect the following error appears :

Cannot open database "dp-name" requested by the login. The login failed. Login failed for user 'Machine\useID'.

How can this error be resolved?

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First I think the connection string should be with |App_Data| not \App_Data\
Second Make sure that this user has permission on this folder and on this DB

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You shouldn't need the AttachDbFileName if your database is already attached, but you should include InitialCatalog to indicate which database you would like to connect to.

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Problem Solved Connection string must be like :

Data Source=.\SQLEXPRESS;AttachDbFileName=|DataDirectory|DB.MDF;" + "Integrated Security=True;User Instance=True";

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Just try to use "|" instead of backslash in your code.