Copy to output directory problem

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C#3.5

I have a question that i have only 1 day to answer it. i dont know why when i set Copy to Output Directory in my database to do not Copy. i get this error when i'm want to connect to the database:
An attempt to attach an auto-named database for file F:\Schoo_Backup\3\Visual Studio 2008\Projects\School_Project1\School_Project1\bin\Debug\SchoolDB.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.
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on my AppConfig i set the connection like this:
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<add name="SchoolDB">
          connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\School.mdf;Integrated Security=True;User Instance=True"
          providerName="System.Data.SqlClient" />

      <add name="School_Project.Properties.Settings.SchoolDBConnectionString">
          connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\SchoolDB.mdf;Integrated Security=True;User Instance=True"
          providerName="System.Data.SqlClient" />
     </add></add>

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I get the StackSource property in exception class:
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at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK)
at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject)
at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart)
at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance)
at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance)
at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection)
at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options)
at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject)
at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject)
at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
at System.Data.SqlClient.SqlConnection.Open()
at System.Data.Linq.SqlClient.SqlConnectionManager.UseConnection(IConnectionUser user)
at System.Data.Linq.SqlClient.SqlProvider.get_IsSqlCe()
at System.Data.Linq.SqlClient.SqlProvider.InitializeProviderMode()
at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)
at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression)
at System.Linq.Queryable.Count[TSource](IQueryable`1 source)
at School_Project.Login.Check_If_Valid() in F:\Schoo_Backup\3\Visual Studio 2008\Projects\School_Project1\School_Project1\Logint.cs:line 27