System.Text.Json requires single-char string to deserialize a char

To successfully deserialize a Char using System.Text.Json, the JSON string must contain a single character.

Change description

In previous .NET versions, a multi-char string in the JSON is successfully deserialized to a char property or field. Only the first char of the string is used, as in the following example:

// .NET Core 3.0 and 3.1: Returns the first char 'a'.
// .NET 5 and later: Throws JsonException because payload has more than one char.
char deserializedChar = JsonSerializer.Deserialize<char>("\"abc\"");

In .NET 5 and later, anything other than a single-char string causes a JsonException to be thrown when the deserialization target is a char. The following example string is successfully deserialized in all .NET versions:

// Correct usage.
char deserializedChar = JsonSerializer.Deserialize<char>("\"a\"");

Version introduced

5.0

Reason for change

Parsing for deserialization should only succeed when the provided payload is valid for the target type. For a char type, the only valid payload is a single-char string.

Recommended action

When you deserialize JSON into a char target, make sure the string consists of a single char.

Affected APIs

• System.Text.Json.JsonSerializer.Deserialize