Question

异常

Cannot deserialize JSON object into type 'System.String'.

控制器

var products = session.Query<Package>().Select(m => new PackageViewModel() {
    Description = m.Description,
    Id = m.Id,
    Title = m.Title,
    Urls = m.Items.Select(g => g.Url).ToArray() //string[] Urls
});

当我将Urls更改为object并将作业Urls设置为m.Items的完整值而不是网址列表时。

通过将上述内容更改为以下内容，它可以正常工作。

var products = session.Query<Package>().ToList();

var viewModel = products.Select(m => new PackageViewModel() {
    Description = m.Description,
    Id = m.Id,
    Title = m.Title,
    Urls = m.Items.Select(g => g.Url).ToArray()
}).ToList();

这真的不是问题，但我想知道我做错了什么。

Full StackTrace

[JsonSerializationException: Cannot deserialize JSON object into type 'System.String'.]
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:417
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:223
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueNonProperty(JsonReader reader, Type objectType, JsonContract contract) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:208
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateList(IWrappedCollection wrappedList, JsonReader reader, String reference, JsonArrayContract contract) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:719
Newtonsoft.Json.Serialization.<>c__DisplayClass1.<CreateAndPopulateList>b__0(IList l, Boolean isTemporaryListReference) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:665
Newtonsoft.Json.Utilities.CollectionUtils.CreateAndPopulateList(Type listType, Action`2 populateList) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Utilities\CollectionUtils.cs:544

Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateAndPopulateList(JsonReader reader, String reference, JsonArrayContract contract) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:653
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateList(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue, String reference) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:446
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:225
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueProperty(JsonReader reader, JsonProperty property, Object target, Boolean gottenCurrentValue, Object currentValue) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:198
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonReader reader, Object target) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:552
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, String id) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:1028
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateAndPopulateObject(JsonReader reader, JsonObjectContract contract, String id) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:858
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:396
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:223

Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueNonProperty(JsonReader reader, Type objectType, JsonContract contract) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:208
Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:120
Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\JsonSerializer.cs:421
Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType) in d:\Development\Releases\Json\Working\Src\Newtonsoft.Json\JsonSerializer.cs:413
Raven.Client.Document.SessionOperations.QueryOperation.DeserializedResult(RavenJObject result) in c:\Builds\raven\Raven.Client.Lightweight\Document\SessionOperations\QueryOperation.cs:173
Raven.Client.Document.SessionOperations.QueryOperation.Deserialize(RavenJObject result) in c:\Builds\raven\Raven.Client.Lightweight\Document\SessionOperations\QueryOperation.cs:139
System.Linq.WhereSelectListIterator`2.MoveNext() +110
System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +327
System.Linq.Enumerable.ToList(IEnumerable`1 source) +58
Raven.Client.Document.SessionOperations.QueryOperation.Complete() in c:\Builds\raven\Raven.Client.Lightweight\Document\SessionOperations\QueryOperation.cs:111
Raven.Client.Document.AbstractDocumentQuery`2.GetEnumerator() in c:\Builds\raven\Raven.Client.Lightweight\Document\AbstractDocumentQuery.cs:551
Raven.Client.Linq.RavenQueryInspector`1.GetEnumerator() in c:\Builds\raven\Raven.Client.Lightweight\Linq\RavenQueryInspector.cs:94
Raven.Client.Linq.RavenQueryInspector`1.System.Collections.IEnumerable.GetEnumerator() in c:\Builds\raven\Raven.Client.Lightweight\Linq\RavenQueryInspector.cs:99
System.Web.Script.Serialization.JavaScriptSerializer.SerializeEnumerable(IEnumerable enumerable, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) +61
System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) +1380
System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat) +194
System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj, StringBuilder output, SerializationFormat serializationFormat) +26
System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj, SerializationFormat serializationFormat) +74
System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj) +6
Mvc.Areas.Api.Controllers.PackagesController.List() in PackagesController.cs:38
lambda_method(Closure , ControllerBase , Object[] ) +96

Answer 1

linq解析器不够智能，无法处理此投影。它可以做简单的投影，但嵌套的东西非常复杂，并且不受支持。您可以使用LuceneQuery API（要加载的字段是“Items，Url”）

来实现

带子查询的Ravendb Select返回完整对象而不是子查询项

异常

控制器

Full StackTrace

1 个答案: