JsonTextReader

JsonTextReader is a concrete implementation of a JSON reader in the Json.NET library (Newtonsoft.Json) for .NET. It reads JSON data from a text source in a forward-only, streaming fashion, emitting tokens as the input is consumed. This makes it suitable for processing large JSON documents or data streams without loading the entire content into memory. The reader implements the standard token-based access pattern, exposing properties such as TokenType and Value, and tracking the current location within the document.

JsonTextReader reads from a TextReader, such as a StreamReader or a StringReader, and is typically used when deserializing with JsonSerializer or when a caller wants to inspect the JSON structure token by token. As the Read method advances, callers can examine the sequence of tokens (for example, StartObject, PropertyName, String, Number, Boolean, Null, EndObject) to perform custom processing or validation. It integrates with the overall Json.NET pipeline, allowing deserialization into strongly typed objects or dynamic structures.

Key usage characteristics include its streaming nature and its ability to work with various text sources that implement TextReader. It supports standard JSON constructs and reports token types and values as parsing progresses. It is common to construct it with a TextReader and wrap it in a using block to ensure proper disposal, or to pass it into a JsonSerializer for object deserialization.

Limitations include its forward-only, token-by-token access, which means random access or full in-memory querying of the input is not available. Its behavior is governed by the Json.NET settings and the input source provided at construction.