Question

当我尝试在模型中展开对象的导航属性时出现错误。

eg. /odata/Products?$expand=ProductDetails

我收到以下错误：

No NavigationLink factory was found for the navigation property 'ProductDetails' from entity type 'ProductModels.Models.Product' on entity set 'Products'. Try calling HasNavigationPropertyLink on the EntitySetConfiguration.

参数名称：navigationProperty

我的模型看起来像这样：

public class Person
{
    public int Id { get; set; }

    public string Name { get; set; }
    [ForeignKey("Name")]
    public PersonDetails PersonDetails { get; set; }
}

public class PersonDetails
{
    [Key]
    public string FullName { get; set; }

    public int Age { get; set; }

}

这是一个零到一的关系，您可以看到我的模型有点奇怪，因为PersonDetails链接到Person by Person.Name = PersonDetails.FullName但实体框架6确实处理它并生成类似SQL的SQL以下内容：

SELECT 
[Extent1].[Id] AS [Id], 
N'f4243347-5b4c-4790-a07d-e8beb80bea72' AS [C1], 
[Extent1].[Name] AS [Name], 
N'PersonDetails' AS [C2], 
N'f4243347-5b4c-4790-a07d-e8beb80bea72' AS [C3], 
[Extent2].[FullName] AS [FullName], 
[Extent2].[Age] AS [Age], 
CASE WHEN ([Extent1].[Name] IS NULL) THEN cast(1 as bit) ELSE cast(0 as bit) END AS [C4]
FROM  [Persons] AS [Extent1]
LEFT OUTER JOIN [PersonDetails] AS [Extent2] ON [Extent1].[Name] = [Extent2].[FullName]

在结果中，许多ProductDetails记录都为null，这没关系。

但似乎OData Formatter在Person.Name为null时遇到问题。我的ProductsContext中有以下设置：

public System.Data.Entity.DbSet<Product> Products { get; set;

这个ODataConventionModelBuilder：

builder.EntitySet<Vehicle>("Products");

我没有ProductDetails的控制器，因为我不想直接访问它，只能通过Products控制器。

如果我添加：

builder.EntitySet<Vehicle>("ProductDetails");

然后我得到了一个：

The EDM instance of type '[ProductModels.Models.ProductDetails Nullable=True]' is missing the property 'FullName'.

这是有道理的，因为FullName在该ProductDetails记录上可能为null。

我能看到的唯一前进方法是使用HasNavigationPropertyLink，而不是像上面那样以标准方式构建ProductDetails。

有人能就我该做什么给我任何建议吗？

Answer 1

将实体条目添加到ODataConfig.cs，如下所示。

builder.EntitySet<EntityName>(typeof(EntityName).Name);

并且整个代码将是这样的

public static class ODataConfig
    {
        public static void Register(HttpConfiguration config)
        {
            ODataModelBuilder builder = new ODataConventionModelBuilder();
            builder.EntitySet<EntityName>(typeof(EntityName).Name);
            var model = builder.GetEdmModel();
            config.Routes.MapODataRoute("odata", "odata", model);

            config.EnableQuerySupport();
        }
    }

Answer 2

试试这段代码：

   var products=builder.EntitySet<Vehicle>("Products");
   products.HasNavigationPropertiesLink(
                product.NavigationProperties,
                (entityContext, navigationProperty) =>
                {
                    object id;
                    entityContext.EdmObject.TryGetPropertyValue("ID", out id);
                    return new Uri(entityContext.Url.Link(ODataTestConstants.DefaultRouteName,
                new
                {
                    odataPath = entityContext.Url.CreateODataLink(
                        new EntitySetPathSegment(entityContext.NavigationSource.Name),
                        new KeyValuePathSegment(id.ToString()),
                        new NavigationPathSegment(navigationProperty))
                }));
                }, true);

Answer 3

这对我有用：

foreach (var navProp in products.EntityType.NavigationProperties)
            {
 products.HasNavigationPropertyLink(
           navprop,
           (entityContext, navigationProperty) =>
           {
               object id;
               entityContext.EdmObject.TryGetPropertyValue("ID", out id);
               return new Uri(entityContext.Url.CreateODataLink(
                     new EntitySetPathSegment(navprop.Name),
                     new KeyValuePathSegment(id.ToString())
                     ));
           }, false);
}

Web API空导航属性

3 个答案: