writeStartDocument

WriteStartDocument is a method of the XmlWriter class used to begin an XML document by emitting the XML declaration. It is available in the .NET Framework, .NET Core, and related .NET platforms that implement XmlWriter.

There are two overloads: WriteStartDocument() and WriteStartDocument(bool standalone). The boolean overload writes a standalone attribute into the declaration to indicate whether the document relies on external markup; the value can be "yes" or "no" depending on the writer’s interpretation.

When invoked, WriteStartDocument causes the writer to emit the XML declaration at the start of the document. The encoding attribute in the declaration is determined by the writer’s output settings or destination; if the encoding is not available (for example when writing to a TextWriter without a definite encoding), the encoding may be omitted. This method does not create or write any root element; you should subsequently call WriteStartElement to create the document’s root.

Usage and lifecycle: WriteStartDocument should be called before any other content is written. If it is called after you have written element content or after EndDocument has already begun, an InvalidOperationException may be thrown. It is typically paired with WriteEndDocument to properly close the document.

See also: WriteStartElement, WriteEndDocument, XmlWriterSettings, and related XmlWriter methods.