We should be able serialize and deserialize from DOM

[terrajobst]

Consider this coding snippet of JSON.NET outlined by @robertmclaws:

public async Task<bool> SomeMethod([FromBody] JObject data)
{
    var model = data.ToObject<SomeObject>();
}

Today, you can't do this with System.Text.Json. I propose we add APIs so that you can write this:

public async Task<bool> SomeMethod([FromBody] JsonElement data)
{
    var model = data.Deserialize<SomeObject>();
}

API Proposal

namespace System.Text.Json
{
    public static partial class JsonSerializer
    {
+    public static TValue? Deserialize<TValue>(this JsonDocument document, JsonSerializerOptions? options = null);
+    public static object? Deserialize(this JsonDocument document, Type returnType, JsonSerializerOptions? options = null);
+    public static TValue? Deserialize<TValue>(this JsonDocument document, JsonTypeInfo<TValue> jsonTypeInfo);
+    public static object? Deserialize(this JsonDocument document, Type returnType, JsonSerializerContext context);

+    public static JsonDocument SerializeToDocument<TValue>(TValue value, JsonSerializerOptions? options = null);
+    public static JsonDocument SerializeToDocument(object? value, Type inputType, JsonSerializerOptions? options = null);
+    public static JsonDocument SerializeToDocument<TValue>(TValue value, JsonTypeInfo<TValue> jsonTypeInfo);
+    public static JsonDocument SerializeToDocument(object? value, Type inputType, JsonSerializerContext context);

+    public static TValue? Deserialize<TValue>(this JsonElement element, JsonSerializerOptions? options = null);
+    public static TValue? Deserialize<TValue>(this JsonElement element, JsonTypeInfo<TValue> jsonTypeInfo);
+    public static object? Deserialize(this JsonElement element, Type returnType, JsonSerializerOptions? options = null);
+    public static object? Deserialize(this JsonElement element, Type returnType, JsonSerializerContext context);

+    public static JsonElement SerializeToElement<TValue>(TValue value, JsonSerializerOptions? options = null);
+    public static JsonElement SerializeToElement(object? value, Type inputType, JsonSerializerOptions? options = null);
+    public static JsonElement SerializeToElement<TValue>(TValue value, JsonTypeInfo<TValue> jsonTypeInfo);
+    public static JsonElement SerializeToElement(object? value, Type inputType, JsonSerializerContext context);

+    public static TValue? Deserialize<TValue>(this JsonNode node, JsonSerializerOptions? options = null);
+    public static TValue? Deserialize<TValue>(this JsonNode node, JsonTypeInfo<TValue> jsonTypeInfo);
+    public static object? Deserialize(this JsonNode node, Type returnType, JsonSerializerOptions? options = null);
+    public static object? Deserialize(this JsonNode node, Type returnType, JsonSerializerContext context);

+    public static JsonNode? SerializeToNode<TValue>(TValue value, JsonSerializerOptions? options = null);
+    public static JsonNode? SerializeToNode(object? value, Type inputType, JsonSerializerOptions? options = null);
+    public static JsonNode? SerializeToNode<TValue>(TValue value, JsonTypeInfo<TValue> jsonTypeInfo);
+    public static JsonNode? SerializeToNode(object? value, Type inputType, JsonSerializerContext context);
    }
}

[ericstj]

Might be a dup of https://github.com/dotnet/corefx/issues/37564

[bjornen77]

Is it possible to add the following to the API proposal?

public static JsonElement SerializeToElement(TValue value);

[robertmclaws]

Any progress on this? Just ran into the issue again in one of my projects. Thanks!

[NoRelect]

I propose to not only have the generics variant, but also one where the Type can be specified as a parameter, so use-cases involving reflection are covered as well. The new API would look like this (Also added the suggestion of @bjornen77):

API Proposal

namespace System.Text.Json
{
    public static partial class JsonSerializer
    {
        public static TValue Deserialize<TValue>(this JsonDocument document);
        public static object Deserialize(this JsonDocument document, Type valueType);
        public static TValue Deserialize<TValue>(this JsonElement element);
        public static object Deserialize(this JsonElement element, Type valueType);

        public static JsonDocument SerializeToDocument<TValue>(TValue value);
        public static JsonDocument SerializeToDocument(object value, Type valueType);
        public static JsonElement SerializeToElement<TValue>(TValue value);
        public static JsonElement SerializeToElement(object value, Type valueType);
    }
}

[cluetjen]

There should be an overload that allows us to pass in serializer options, e.g. custom converters.