SqlException (0x80131904):无法附加文件

我有一个c# ASP。. NET MVC应用程序连接到同一文件夹中的本地mdf数据库文件，在web.config:

<connectionStrings>
    <add name="ImportNUS" 
         connectionString="Data Source=(LocalDB)'MSSQLLocalDB; AttachDbFileName=C:'Users'Chase'Desktop'DDAC Assignment'DDAC Assignment - CMS'CMS Databases'N.US.mdf;Initial Catalog=NUS, Integrated Security=true;" 
         providerName="System.Data.SqlClient" />
</connectionStrings>

和this:

@{
var DB = Database.Open("ImportNUS");
var selectQueryString = "SELECT * FROM IMPORT ORDER by Customer ID";}
   <div id="Import" class="tab-pane fade">
            <h3>Import</h3>
            <table>
                <thead>
                    <tr>
                        <th>Id</th>
                        <th>Product</th>
                        <th>Description</th>
                    </tr>
                </thead>
                    @foreach(var row in DB.Query(selectQueryString)){ 
                    <tr>
                        <td>@row.Container ID</td>
                        <td>@row.Warehouse ID</td>
                        <td>@row.Imported From</td>
                    </tr>
                    }
                  }
                }
            </table>
        </div>

我得到这个错误:

[SqlException (0x80131904): Cannot attach file 'C:'Users'Chase'Desktop'DDAC Assignment'DDAC Assignment - CMS'CMS Databases'N.US.]mdf' as database 'NUS, Integrated Security=true'，因为这个文件已经被数据库'NUS, Container ID=containerid,Warehouse ID=WarehouseID, import From=IF']

这事已经困扰我好几天了。对不起，我是新手，但是你能给我一些建议如何解决这个问题吗?我真的很感激。我只是想连接到.mdf数据库文件