Question

寻找关于最佳方法/模式的输入，以满足视图模型类的以下要求：

将IQueryable从存储库选择转换为IQueryable视图模型查询＆lt; - 正常工作
将db实体的单个实例转换为视图模型实例＆lt; - 不工作，返回NULL
两者都使用单个方法将db实体映射到视图模型属性以避免映射复制

我正在尝试的例子，但它不起作用......似乎有点像黑客：

public class WorkOrderDependencyViewModel : IEntity, IViewModel<WorkOrderDependency, WorkOrderDependencyViewModel>
{
    public int Id { get; set; } }
    public int WorkOrderHeaderId { get; set; }
    public int POHeaderId { get; set; }      
    public decimal RemainQty { get; set; }

    //Re-use this mapping logic for both converting a query and converting a single db entity instance. Used by Kendo Grids
    public IQueryable<WorkOrderDependencyViewModel> ConvertClassQueryToViewModelQuery(IQueryable<WorkOrderDependency> entityQuery)
    {
        var viewModelResultQuery = entityQuery
            .Select(x => new WorkOrderDependencyViewModel()
            {
                Id = x.Id,
                WorkOrderHeaderId = x.WorkOrderHeaderId,
                POHeaderId = x.PODetail.POHeaderId,
                RemainQty = x.PODetail.QtyOrdered - x.PODetail.QtyReceived
            }
        );

        return viewModelResultQuery;
    }

    //convert single instance of db entity to view model, but use existing mapping logic from above method
    public WorkOrderDependencyViewModel ConvertClassToViewModel(WorkOrderDependency entity)
    {
        var entityList = new List<WorkOrderDependency>();
        entityList.Add(entity);
        var viewModel = ConvertClassQueryToViewModelQuery(entityList.AsQueryable()).FirstOrDefault() as WorkOrderDependencyViewModel;
        return viewModel; <------ viewModel is NULL
    }
}

为什么viewModel返回NULL？

Answer 1

如果您不需要IQueryable，这将是一个更短更简单的方法

public WorkOrderDependencyViewModel ConvertClassToViewModel(
    WorkOrderDependency entity)
{
    return new WorkOrderDependencyViewModel 
    {
        Id = entity.Id,
        WorkOrderHeaderId = entity.WorkOrderHeaderId,
        POHeaderId = entity.PODetail.POHeaderId,
        RemainQty = entity.PODetail.QtyOrdered - entity.PODetail.QtyReceived
    };
}

修改如果你使用它作为linq查询的一部分，也许你可以使用Automapper或像这样的函数

private static readonly Expression<Func<WorkOrderDependency, WorkOrderDependencyViewModel>> AsViewModel = entity => new WorkOrderDependencyViewModel { Id = entity.Id, WorkOrderHeaderId = entity.WorkOrderHeaderId, POHeaderId = entity.PODetail.POHeaderId, RemainQty = entity.PODetail.QtyOrdered - entity.PODetail.QtyReceived };

您可以在查询中使用它

public IQueryable<WorkOrderDependencyViewModel> GetViewModel() { return repository.WorkOrderDependencies // change to suit your query needs .Select(AsViewModel); }

视图模型创建的最佳方法是处理单个实体和列表 - 返回IQueryable

1 个答案: