JSON with serde_json

Use case

You need to read and write JSON: API payloads, config files, or any structured data. The serde_json crate with serde gives type-safe serialization and deserialization.

In C#: Like System.Text.Json or Newtonsoft: serialize/deserialize to and from classes. In Rust, derive Serialize/Deserialize and use serde_json::from_str/to_string.

Deserializing JSON

Define a struct with Deserialize (and optionally Serialize). Use serde_json::from_str for a string or serde_json::from_reader for a file/stream.

use serde::Deserialize;

#[derive(Deserialize)]
struct User {
    id: i32,
    name: String,
    email: Option<String>,
}

let json = r#"{"id": 1, "name": "Alice", "email": "alice@example.com"}"#;
let user: User = serde_json::from_str(json)?;

In C#: Like JsonSerializer.Deserialize<User>(json). Use Option<T> for nullable fields.

Serializing to JSON

Derive Serialize and use serde_json::to_string or serde_json::to_writer.

use serde::Serialize;

#[derive(Serialize)]
struct Response {
    status: String,
    count: u32,
}

let res = Response { status: "ok".into(), count: 42 };
let json = serde_json::to_string(&res)?;

In C#: Like JsonSerializer.Serialize(res).

Value and arbitrary JSON

When the structure is dynamic, use serde_json::Value: Value::Object, Value::Array, Value::String, etc. Parse with serde_json::from_str::<Value>(s)? and index or match on the value.

In C#: Like JsonElement or JObject/JArray in Newtonsoft.

Key takeaway

Use serde_json::from_str/to_string with structs that derive Serialize/Deserialize. Use serde_json::Value for dynamic JSON. All operations return Result; use ? or handle errors.