runtime: ',' is invalid after a single JSON value. Expected end of data.
I am reading a single complex object from a FileStream using JsonSerializer.ReadAsync<T>(stream, options, token) and I seriously just want the one value, but I am getting this exception.
',' is invalid after a single JSON value. Expected end of data.
The JSON in the file is preceded by bytes which I have skipped or already processed and it is followed by more bytes which I can skip or process separately. However I get stuck by this exception and don’t get the value that is presumably correctly read.
I have no idea how long the value is. Pre-parsing the JSON at a lower level to just get the byte length is a bad solution.
Wouldn’t it be better to not throw in this situation and let the consumer of the API choose to check for end of stream?
Similar to dotnet/runtime#29947.
About this issue
- Original URL
- State: closed
- Created 5 years ago
- Reactions: 1
- Comments: 30 (21 by maintainers)
It’s good to point this out in case people with corrupt data end up on this issue by searching for the error message, but I want to make it clear that this issue isn’t about corrupt data, but about a design limitation in System.Text.Json that makes it impossible to intentionally decode a JSON value from the middle of a stream.
Note that there is another approach you can use: call
stream.SetLength(stream.Position)after serializing to it but before closing the file.Mm,
DeserializeAsyncEnumerableI believe does cover my usage. It only applies to arrays at the root, but that’s precisely my situation.