对代码和 NHibernate QueryOver 使用相同的规范<t></t>

Question

Scenario

I'm working on an application that has a little section dedicated to displaying statistics about the current state of the system. This includes such things as how many items are overdue, count of all pending items, count of all items without filters. When the user opens the application they must select which item labels they wish to work on before seeing any items in the UI. Once that is done the database gets queried and returns a list back to the user. Each item has an associated label. The item label is auto-generated before the users see it. One of these labels could be "Overdue", which indicates to the user that it should be completed first.

Problem

I'm struggling to find a good way to centralize the logic that determines if an item is overdue.

The way I do this now is simple create a Future NHibernate query and do all my statistic counts in one database transaction. The issue is that once I retrieve the items from the database (which is already assigned a label, but if an item is overdue the system is supposed to override the label). So once the data is retrieved (after the users select their labels) I parse it into a tree and need to check each item whether it's overdue or not. The logic is quite simple but located in 2 places because two different parts of the system need it for different purposes.

My view model bound to my UI contains this:

public bool IsOverdue
{
    get
    {
        return
            LabelName == "Please Advise" &&
            DateTimeProvider.Current.DateTime.AddDays(2) > WorkToBeginDateTime;
    }
}

public void TakeActionIfOverdue()
{
    if(IsOverdue)
    {
        LabelName = "Overdue";
        LabelBackground = "#123456";
    }
}

I call TakeActionIfOverdue() whenever I'm building my tree, which overrides the label name if required.

And my NHibernate query looks like this:

Domain.Locate locateAlias = null;
Status statusAlias = null;

var overdueCountQuery = _session.QueryOver(() => locateAlias)
    .Select(Projections.RowCount())
    .JoinAlias(() => locateAlias.Status, () => statusAlias)
    .Where(() => statusAlias.Name == "Please Advise")
    .Where(() => locateAlias.WorkToBeginDateTime
        .IsBetween(DateTimeProvider.Current.DateTime.Subtract(new TimeSpan(48, 0, 0)))
        .And(DateTimeProvider.Current.DateTime))
    .Where(() => locateAlias.IsComplete == false)
    .FutureValue<int>();

As you can see the logic determining if an item is overdue is in two places.

My TreeView (which gets parsed and displayed once the user selects which label they'd like to see) looks like this.

- Some Heading
    - Item #1 (Foo Label)
    - Item #3 (Bar Label)
- Another Heading
    - Item #2 (Bar Label)
    - Item #4 (Bar Label)
    - Item #6 (Overdue)

In this scenario the user selected label Foo Label and Bar Label . For the sake of this example, let's pretend Item #6 had label Bar Label . However, the UI is displaying that it has label Overdue because it was due 2 days ago.

And my little statistics box looks like this.

Items Overdue: 4
Pending Items: 45
All Items: 49

Question

How can I centralize this logic?

Answer 1

Use the QueryOver library to build the your Specifications classes without performance issues and with fluent features of the QueryOver. The only issue is the dependency with the NHibernate, since the LINQ should be the default model to execute queries.

        var list =
            repository.Find(courseWithVotes.By().And(courseByExample.By(new Course() { Name = "ava" })));

Examples: http://queryoverspec.codeplex.com/