How to Deserialize JSON into an IEnumerable using Newtonsoft.Json.NET?

Using Newtonsoft.Json.NET to Deserialize JSON into an IEnumerable Collection

Challenge:

Deserializing complex JSON data into an IEnumerable<BaseType> where BaseType is abstract presents difficulties. Standard JsonConvert.DeserializeObject() fails because of the abstract base type.

Resolution:

The solution involves leveraging JsonSerializerSettings and its TypeNameHandling property. Setting TypeNameHandling to All ensures that the serialized JSON includes $type fields, preserving type information crucial for deserialization.

Implementation Steps:

1. Configure Serialization: Create a JsonSerializerSettings object and set TypeNameHandling to All.

<code class="language-csharp">JsonSerializerSettings settings = new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.All
};</code>

2. Serialize with Type Information: Serialize your object using the configured settings. This adds the necessary $type fields to the JSON string.

<code class="language-csharp">string strJson = JsonConvert.SerializeObject(instance, settings);</code>

The resulting JSON will resemble this (note the $type fields):

<code class="language-json">{
  "$type": "System.Collections.Generic.List`1[[MyAssembly.BaseClass, MyAssembly]], mscorlib",
  "$values": [
    {
      "$id": "1",
      "$type": "MyAssembly.ClassA, MyAssembly",
      "Email": "[email'\u00a0protected]"
    },
    {
      "$id": "2",
      "$type": "MyAssembly.ClassB, MyAssembly",
      "Email": "[email'\u00a0protected]"
    }
  ]
}</code>

3. Deserialize with Type Information: Deserialize the JSON string back into an IEnumerable<BaseType> using the same settings object.

<code class="language-csharp">IEnumerable<BaseType> deserialized = JsonConvert.DeserializeObject<IEnumerable<BaseType>>(strJson, settings);</code>

Relevant Documentation:

• TypeNameHandling Setting

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