使用 OData 控制器自动展开相关实体

Question

我有这些课程：

    public class Items
    {
    [Key]
    public Guid Id { get; set; }
    public string ItemCode { get; set; }
    public decimal SalesPriceExcl { get; set; }
    public decimal SalesPriceIncl { get; set; }

    public virtual ICollection<ItemPrice> SalesPrices { get; set; }

    public Items()
    {
        SalesPrices = new HashSet<App4Sales_ItemPrice>();
    }
}

 public class ItemPrice
{
    [Key, Column(Order = 0), ForeignKey("Items")]
    public Guid Id { get; set; }
    public virtual Items Items { get; set; }

    [Key, Column(Order=1)]
    public Guid PriceList { get; set; }        
    public decimal PriceExcl { get; set; }
    public decimal PriceIncl { get; set; }
    public decimal VatPercentage { get; set; }        

}

我想查询 Items 并自动获取 ItemPrice 集合。

我创建了一个 OData V3 控制器：

    // GET: odata/Items
    //[Queryable]
    public IQueryable<Items> GetItems(ODataQueryOptions opts)
    {
        SelectExpandQueryOption expandOpts = new SelectExpandQueryOption(null, "SalesPrices", opts.Context);
        Request.SetSelectExpandClause(expandOpts.SelectExpandClause);
        return expandOpts.ApplyTo(db.Items.AsQueryable(), new ODataQuerySettings()) as IQueryable<Items>;


    }

但我得到了错误： “无法序列化空提要”

是的，有些商品没有 ItemPrice 清单。

我可以克服这个错误，还是可以做一些不同的事情？

亲切的问候

杰伦

我发现潜在的错误是： 无法转换类型的对象 'System.Data.Entity.Infrastructure.DbQuery1[System.Web.Http.OData.Query.Expressions.SelectExpandBinder+SelectAllAndExpand1[.Models.Items]]' 输入“.Models.Items”。

Answer 1

在上面https://stackoverflow.com/a/43339286/507421 并添加一种获取选择和扩展属性的方法

public static IQueryable<T> ApplyODataOptions<T>(this IQueryable<T> query, ODataQueryOptions options) where T : new()
{
    if (options == null)
    {
        return query;
    }

    var queryable = options.ApplyTo(query);
    if (queryable is IQueryable<T> queriableEntity)
    {
        return queriableEntity;
    }
    var results = new List<T>();
    foreach (var item in queryable)
    {
        var instanceProp = item.GetType().GetProperty("Instance");
        var value = (T)instanceProp.GetValue(item) ?? new T();
        results.Add(value);

        var containerProp = item.GetType().GetProperty("Container");
        var container = containerProp.GetValue(item);
        while (container != null)
        {
            var containerType = container.GetType();
            var containerValue = containerType.GetProperty("Value").GetValue(container);
            var containerName = containerType.GetProperty("Name").GetValue(container) as string;
            var expandedProp = typeof(T).GetProperty(containerName);
            if (containerValue is IEnumerable containerValues)
            {
                var listType = typeof(List<>).MakeGenericType(expandedProp.PropertyType.GenericTypeArguments[0]);
                var expandedList = (IList)Activator.CreateInstance(listType);
                foreach (var expandedItem in containerValues)
                {
                    var expandedInstanceProp = expandedItem.GetType().GetProperty("Instance");
                    var expandedValue = expandedInstanceProp.GetValue(expandedItem);
                    expandedList.Add(expandedValue);
                }
                expandedProp.SetValue(value, expandedList);
            }
            else
            {
                expandedProp.SetValue(value, containerValue);
            }
            container = containerType.GetProperty("Next0")?.GetValue(container);
        }
    }
    return results.AsQueryable<T>();
}

Answer 2

我在看到这个帖子后解决了这个问题：http://www.jauernig-it.de/intercepting-and-post-processing-odata-queries-on-the-server/

这是我现在的控制器：

SelectExpandQueryOption expandOpts = new SelectExpandQueryOption(null, "SalesPrices", opts.Context);

        Request.SetSelectExpandClause(expandOpts.SelectExpandClause);

        var result = expandOpts.ApplyTo(db.Items.AsQueryable(), new ODataQuerySettings());
        var resultList = new List<Items>();

        foreach (var item in result)
        {
            if (item is Items)
            {
                resultList.Add((Items)item);
            }
            else if (item.GetType().Name == "SelectAllAndExpand`1")
            {
                var entityProperty = item.GetType().GetProperty("Instance");
                resultList.Add((Items)entityProperty.GetValue(item));
            }
        }


        return resultList.AsQueryable();

杰伦

Answer 3

GetItems([FromODataUri] ODataQueryOptions queryOptions)