使用相同datacontext的多个查询引发SqlException

我尝试用我的搜索类型来实现搜索。我使用linqtosql对数据库进行查询。虽然它通常工作得很好,但是当用户输入查询的速度非常快时,会抛出一些随机的SqlException。以下是我最近偶然发现的两个不同的错误消息:

读卡器关闭时调用Read的尝试无效。

DataContextFactory类:

public DataContextFactory(IConnectionStringFactory connectionStringFactory)
{
    this.dataContext = new RegionDataContext(connectionStringFactory.ConnectionString);
}

public DataContext Context
{
    get { return this.dataContext; }
}

public void SaveAll()
{
    this.dataContext.SubmitChanges();
}

向Unity注册IDataContextFactory

// Get connection string from Application.Current settings
ConnectionInfo connectionInfo = Application.Current.Properties["ConnectionInfo"] as ConnectionInfo;
// Register ConnectionStringFactory with Unity container as a Singleton
this.container.RegisterType<IConnectionStringFactory, ConnectionStringFactory>(new ContainerControlledLifetimeManager(),
    new InjectionConstructor(connectionInfo.ConnectionString));
// Register DataContextFactory with Unity container
this.container.RegisterType<IDataContextFactory, DataContextFactory>();

Data Source=.\SQLEXPRESS2008;User Instance=true;Integrated Security=true;AttachDbFilename=C:\client.mdf;MultipleActiveResultSets=true;

// IDataContextFactory dependency is injected by Unity
public CompanyRepository(IDataContextFactory dataContextFactory)
{
    this.dataContextFactory = dataContextFactory;
}

// return List<T> of companies
var results = this.dataContextFactory.Context.GetTable<CompanyEntity>()
        .Join(this.dataContextFactory.Context.GetTable<RegionEntity>(),
            c => c.regioncode,
            r => r.regioncode,
            (c, r) => new { c = c, r = r })
        .Where(t => t.c.summary_region != null)
        .Select(t => new { Id = t.c.compcode, Company = t.c.compname, Region = t.r.regionname }).ToList();

周围的工作是什么?