# Data at the root level is invalid

Source: https://xmlvalid.com/errors/data-at-the-root-level-is-invalid

> The input does not start with markup: it is not XML, or something comes before the root element.

The message, as .NET reports it: `Data at the root level is invalid. Line 1, position 1.`

## Why it happens

- A file path passed to `XmlDocument.LoadXml()`, which expects the XML text itself; use `Load()` for a path or stream.
- The input is not XML: an HTML error page, JSON, or a server message.
- Bytes before the first `<`: a byte order mark in a string read with the wrong encoding, or text before the root.

## How to fix it

- Check what you pass: `LoadXml` and `XDocument.Parse` take XML text, `Load` takes a path, URI or stream. Then look at the first characters of the input; for a stream, let `XmlReader` detect the encoding instead of decoding it yourself.
- .NET throws an `XmlSchemaValidationException` at the first schema error unless `XmlReaderSettings.ValidationEventHandler` is set, which then receives every one with its line and position. A well-formedness error is an `XmlException` and ends reading whatever the settings.

## The same problem in xmlvalid

libxml2, which xmlvalid validates with, reports it as [Start tag expected, '<' not found](https://xmlvalid.com/errors/start-tag-expected): `Start tag expected, '<' not found`

## Example that fails

```xml
hello <note/>
```

## Fixed

```xml
<note>hello</note>
```