f# - ODataService 类型提供程序的可为空整数不存在属性 'HasValue'

Question

我正在尝试将 ODataService 类型提供程序与 Netflix 一起使用。这工作正常:

type internal NetflixData = ODataService<"http://odata.netflix.com/Catalog/">
let internal NetflixContext = NetflixData.GetDataContext()

let godzillamovies = query { for t in NetflixContext.Titles do 
                             where (t.Name.Contains "Godzilla")
                             select (t.Name, t.ReleaseYear)
                           } |> Seq.toList

但返回哥斯拉电视节目的所有剧集，没有发布年份(嘘)。因此，我将查询更新为:

let godzillamovies = query { for t in NetflixContext.Titles do 
                             where (t.Name.Contains "Godzilla" && t.ReleaseYear.HasValue)
                             select (t.Name, t.ReleaseYear.Value)
                           } |> Seq.toList

我遇到了以下错误:

<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\"?>
<error xmlns=\"http://schemas.microsoft.com/ado/2007/08/dataservices/metadata\">
  <code></code>
  <message xml:lang=\"en-US\">No property 'HasValue' exists in type 'System.Nullable`1[[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' at position 45.</message>
</error>

呃，可空整数不存在 HasValue 吗？从何时起？

Answer 1

#r "FSharp.Data.TypeProviders"
#r "System.Data.Services.Client"

open Microsoft.FSharp.Data.TypeProviders
open Microsoft.FSharp.Linq.NullableOperators

type internal NetflixData = ODataService<"http://odata.netflix.com/Catalog/">
let internal NetflixContext = NetflixData.GetDataContext()

NetflixContext.DataContext.SendingRequest.Add(fun e -> printfn "%A" e.Request.RequestUri)

// http://odata.netflix.com/Catalog/Titles()?$filter=substringof('Godzilla',Name) and (ReleaseYear ne null)&$select=Name,ReleaseYear
let godzillamovies = query { for t in NetflixContext.Titles do 
                             where (t.Name.Contains "Godzilla")
                             where (t.ReleaseYear ?<>? System.Nullable())
                             select (t.Name, t.ReleaseYear)
                           } |> Seq.toList