خطا در Restore کردن بانک

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سلام دوستان
بنده در Vb.net 2008 با این کانکشن و این کد بدون خطا از بانک پک آپ می گیریم

کد:

Dim strcon As String = "Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|File.mdf;Integrated Security=True;User Instance=True"

و

کد:

Dim command As String = "backup database  [" + dbname + "] to disk='" + strfilename + "'"

حال وقتی می خواهم این فایل رو با این کدها Restore کنم خطای زیر را می گیرد

کد:

Dim cmd As New SqlCommand


        cmd.Connection = New SqlConnection("Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|File.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True")
        cmd.Connection.Open()
        Dim dbname As String = cmd.Connection.Database




        cmd.Connection.Close()


        Dim query As String = "ALTER DATABASE [" + dbname + "] SET SINGLE_USER WITH ROLLBACK IMMEDIATE ;RESTORE DATABASE [" + dbname + "] FROM DISK = '" + Application.StartupPath + "\backup.bak';ALTER DATABASE [" + dbname + "] SET MULTI_USER ;"
        cmd.Connection = New SqlConnection("Data Source=.\sqlexpress;Integrated Security=True;Connect Timeout=30;User Instance=True")
        cmd.Connection.Open()
        cmd.CommandText = query
        cmd.ExecuteNonQuery()
        cmd.Connection.Close()

پیغام خطا

کد:

The tail of the log for the database "Filename" has not been backed up. Use BACKUP LOG WITH NORECOVERY to backup the log if it contains work you do not want to lose. Use the WITH REPLACE or WITH STOPAT clause of the RESTORE statement to just overwrite the contents of the log. RESTORE DATABASE is terminating abnormally. Nonqualified transactions are being rolled back. Estimated rollback completion:

ممنون