无法访问已处置的对象 [英] Cannot access a disposed object

问题描述

在测试使用LINQ to SQL的DAL库时，我遇到了一个问题

i'm facing a issue while testing the DAL Library which uses LINQ to SQL

正在测试的方法如下(一个简单的方法):

Method that is being Tested as below (a simple one):

public List<tblAccount> GetAccountsByCustomer(tblCustomer customer)
{
    using (OnlineBankingDataClassesDataContext dbcntx = new OnlineBankingDataClassesDataContext())
    {
        var accounts = dbcntx.tblAccounts.Where(p => p.tblCustomer.ID.CompareTo(customer.ID)==0);
        return accounts.ToList<tblAccount>();
    }
}

测试代码如下:

static tblCustomer GetTopOneCustomer()
{
    OnlineBankingDataClassesDataContext dbcntx = new OnlineBankingDataClassesDataContext();
    var customers = dbcntx.tblCustomers.Take(1);
    return customers.Single<tblCustomer>();
}

public static void Should_List_All_Account_By_Customer()
{

    tblCustomer customer = GetTopOneCustomer();

    DataController dc = new DataController();
    List<tblAccount> accounts=dc.GetAccountsByCustomer(customer);
    foreach (tblAccount account in accounts)
    {
        string accountdetails=string.Format("Account ID:{0} \n Account Type:{1} \n Balance:{2} \n BranchName:{3} \n AccountNumber:{4}",
                        account.ID.ToString(), account.tblAccountType.Name, 
                        account.Balance.ToString(),
                        account.tblBranch.Name, account.Number);

        Console.WriteLine(accountdetails);

    }
}

我收到错误消息无法访问已处置的对象".在这种情况下访问关联的对象时，我正在使用account.tblAccountType.Name.我知道它与DataContext有关.我应该如何使此代码正常工作.

I'm getting an error "Cannot access a disposed object." when accessing associated object like in this case, I'm using account.tblAccountType.Name. I know it has something to do with DataContext. How shall I get this code working.

推荐答案

dbcntx是一次性对象.调用GetTopOneCustomer()后，垃圾收集器可以随时出现并进行处理.看起来正在发生什么.

dbcntx is a disposable object. The Garbage Collector can come along at any time after GetTopOneCustomer() has been called and dispose of it. Which is what looks like is happening.

尝试将GetTopOneCustomer()更改为:

static tblCustomer GetTopOneCustomer(OnlineBankingDataClassesDataContext dataContext) 
{
    //Stuff
}

然后在Should_List_All_Account_By_Customer()内部将其更改为:

Then inside Should_List_All_Account_By_Customer() change it like so:

using (OnlineBankingDataClassesDataContext dataContext = new OnlineBankingDataClassesDataContext())
{
    tblCustomer customer = GetTopOneCustomer(dataContext); 
    //More Stuff
}

这样，您可以控制dataContext的生存期.

This way you control the lifetime of the dataContext.

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