[英]Proper way to call nested Expand() from .NET OData 4 Client
In an OData 4 service on Web API, what is the proper way to call nested $expand from a .NET client?在 Web API 上的 OData 4 服务中,从 .NET 客户端调用嵌套 $expand 的正确方法是什么? We are using the OData Client Generator .
我们正在使用OData 客户端生成器。 Back in the prior WCF Data Services with OData 3 service we could call
.Expand("Customers/Orders")
.回到带有 OData 3 服务的先前 WCF 数据服务中,我们可以调用
.Expand("Customers/Orders")
。 In Web API with OData 4 we can no longer do so and receive the following should you attempt .Expand("Customers/Orders")
:在带有 OData 4 的 Web API 中,如果您尝试
.Expand("Customers/Orders")
我们将无法再这样做并收到以下信息:
The query specified in the URI is not valid.
URI 中指定的查询无效。 Found a path traversing multiple navigation >properties.
找到了一条遍历多个导航 > 属性的路径。 Please rephrase the query such that each expand path contains only type >segments and navigation properties.
请重新表述查询,使每个展开路径仅包含类型 > 段和导航属性。
We are able to work around this by calling expand like so: .Expand("Customers($expand=Orders)")
.我们可以通过像这样调用 expand 来解决这个问题:
.Expand("Customers($expand=Orders)")
。 In non-nested $expand scenarios, I like the lambda support like so .Expand(d => d.Customers)
.在非嵌套的 $expand 场景中,我喜欢像这样的 lambda 支持
.Expand(d => d.Customers)
。 Is there a proper way in .NET OData 4 client to call nested expands without the unfortunate magic string of .Expand("Customers($expand=Orders)")
?在 .NET OData 4 客户端中是否有正确的方法来调用嵌套扩展而没有
.Expand("Customers($expand=Orders)")
的不幸魔法字符串? If not, is there a cleaner string pattern like "Customers/Orders" that would work?如果没有,是否有像“客户/订单”这样的更清晰的字符串模式可以工作? Thanks.
谢谢。
The request that you want to send is:您要发送的请求是:
GET http://host/service/Customers/Orders
right?对?
According to the OData protocol:根据 OData 协议:
To request related entities according to a particular relationship, the client issues a GET request to the source entity ’s request URL, followed by a forward slash and the name of the navigation property representing the relationship.
要根据特定关系请求相关实体,客户端向源实体的请求 URL 发出 GET 请求,后跟正斜杠和表示关系的导航属性的名称。
So such request is not supported as the "Customers" before "/Orders" is the name of an entity set instead of a single entity.因此,不支持此类请求,因为“/Orders”之前的“Customers”是实体集的名称,而不是单个实体。 You can only write nested expanding like:
您只能编写嵌套扩展,例如:
GET http://host/service/Customers(1)/Orders
Which corresponds to the following code snippets using OData V4 Code Generator:这对应于以下使用 OData V4 代码生成器的代码片段:
var orders = context.Customers.ByKey(new Dictionary<string, object>() { { "ID", 1 } }).Orders.Execute();
And you need to iterate through all the customers to get all their orders.并且您需要遍历所有客户以获取他们的所有订单。
A little extension for that :对此的一点扩展:
public static DataServiceQuery<TSource> Expand<TSource,TNavigation,TExpand>(this DataServiceQuery<TSource> dataServiceQuery, Expression<Func<TSource, DataServiceCollection<TNavigation>>> expression, Expression<Func<TNavigation,TExpand>> navigation)
{
var expressionName = (expression.Body as System.Linq.Expressions.MemberExpression).Member.Name;
var navigationName = (navigation.Body as System.Linq.Expressions.MemberExpression).Member.Name;
return dataServiceQuery.Expand($"{expressionName}($expand={navigationName})");
}
Now you have intellisense and type checking现在你有了智能感知和类型检查
Example :例子 :
db.Container.Expand(c=> c.Customers, customer => customer.Orders) db.Container.Expand(c=> c.Customers, customer => customer.Orders)
In OData v4, it is not valid to expand multi levels, such as what you mentioned in the question: .Expand("Customers/Orders").在 OData v4 中,扩展多级是无效的,例如您在问题中提到的:.Expand("Customers/Orders")。 I dont think the client will support such API.
我不认为客户端会支持这样的 API。 Here is what in the ABNF http://docs.oasis-open.org/odata/odata/v4.0/os/abnf/odata-abnf-construction-rules.txt :
这是 ABNF http://docs.oasis-open.org/odata/odata/v4.0/os/abnf/odata-abnf-construction-rules.txt 中的内容:
expand = '$expand' EQ expandItem *( COMMA expandItem )
expandItem = STAR [ ref / OPEN levels CLOSE ]
/ expandPath
[ ref [ OPEN expandRefOption *( SEMI expandRefOption ) CLOSE ]
/ count [ OPEN expandCountOption *( SEMI expandCountOption ) CLOSE ]
/ OPEN expandOption *( SEMI expandOption ) CLOSE
]
expandPath = [ qualifiedEntityTypeName "/" ]
*( ( complexProperty / complexColProperty ) "/" [ qualifiedComplexTypeName "/" ] )
navigationProperty
[ "/" qualifiedEntityTypeName ]
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