实体框架4在删除对象时抛出System.Data.UpdateException

Question

我正在使用EF4.0并试图从数据库中删除一条记录，但是我的代码一直抛出以下异常：

System.Data.UpdateException类型的第一次例外发生在System.Data.Entity.dll中

这是我的密码：

public bool ApproveUser(string username)  
{
    using (var context = new UserRegistrationEntities())
    {
        // The entry object gets populated correctly
        var entry = context.PendingApprovals
                .Where(e => e.Username.Equals(username))
                .FirstOrDefault();
        try
        {
            context.DeleteObject(entry);
            // Also tried context.PendingApprovals.DeleteObject(entry)
            context.SaveChanges();
            return true;
        }
        catch
        {
            return false;
        }
    }
}

我已经完成了代码，异常将被抛出到context.SaveChanges();

我有遗漏什么吗？任何帮助都将不胜感激！

提前感谢

Answer 1

您是否设置了断点并查看条目是否有值？尝尝这个?

public bool ApproveUser(string username)  
{
    using (var context = new UserRegistrationEntities())
    {
        // The entry object gets populated correctly
        var entry = context.PendingApprovals
                .First(e => e.Username.Equals(username))
        if (entry != null) {
        try
        {
            context.PendingApprovals.DeleteObject(entry);
            context.SaveChanges();
            return true;
        }
        catch
        {
            return false;
        }
        }
    }
    return false;
}

Answer 2

先试着移除它：

public bool ApproveUser(string username)  
{
    using (var context = new UserRegistrationEntities())
    {
        // The entry object gets populated correctly
        var entry = context.PendingApprovals
                .Where(e => e.Username.Equals(username))
                .FirstOrDefault();
        try
        {
            context.PendingApprovals.Remove(entry);
            context.DeleteObject(entry);
            // Also tried context.PendingApprovals.DeleteObject(entry)
            context.SaveChanges();
            return true;
        }
        catch
        {
            return false;
        }
    }
}