Mono.Xml.XmlTextWriter.WriteStartAttribute C# (CSharp) Method

		public override void WriteStartAttribute (
			string prefix, string localName, string namespaceUri)
		{
			// LAMESPEC: this violates the expected behavior of
			// this method, as it incorrectly allows unbalanced
			// output of attributes. Microfot changes description
			// on its behavior at their will, regardless of
			// ECMA description.
			if (state == WriteState.Attribute)
				WriteEndAttribute ();

			if (state != WriteState.Element && state != WriteState.Start)
				throw StateError ("Attribute");

			if ((object) prefix == null)
				prefix = String.Empty;

			// For xmlns URI, prefix is forced to be "xmlns"
			bool isNSDecl = false;
			if (namespaceUri == XmlnsNamespace) {
				isNSDecl = true;
				if (prefix.Length == 0 && localName != "xmlns")
					prefix = "xmlns";
			}
			else
				isNSDecl = (prefix == "xmlns" ||
					localName == "xmlns" && prefix.Length == 0);

			if (namespaces) {
				// MS implementation is pretty hacky here. 
				// Regardless of namespace URI it is regarded
				// as NS URI for "xml".
				if (prefix == "xml")
					namespaceUri = XmlNamespace;
				// infer namespace URI.
				else if ((object) namespaceUri == null) {
					if (isNSDecl)
						namespaceUri = XmlnsNamespace;
					else
						namespaceUri = String.Empty;
				}

				// It is silly design - null namespace with
				// "xmlns" are allowed (for namespace-less
				// output; while there is Namespaces property)
				// On the other hand, namespace "" is not 
				// allowed.
				if (isNSDecl && namespaceUri != XmlnsNamespace)
					throw ArgumentError (String.Format ("The 'xmlns' attribute is bound to the reserved namespace '{0}'", XmlnsNamespace));

				// If namespace URI is empty, then either prefix
				// must be empty as well, or there is an
				// existing namespace mapping for the prefix.
				if (prefix.Length > 0 && namespaceUri.Length == 0) {
					namespaceUri = nsmanager.LookupNamespace (prefix, false);
					if (namespaceUri == null || namespaceUri.Length == 0)
						throw ArgumentError ("Namespace URI must not be null when prefix is not an empty string.");
				}

				// Dive into extremely complex procedure.
				if (!isNSDecl && namespaceUri.Length > 0)
					prefix = DetermineAttributePrefix (
						prefix, localName, namespaceUri);
			}

			if (indent_attributes)
				WriteIndentAttribute ();
			else if (state != WriteState.Start)
				writer.Write (' ');

			if (prefix.Length > 0) {
				writer.Write (prefix);
				writer.Write (':');
			}
			writer.Write (localName);
			writer.Write ('=');
			writer.Write (quote_char);

			if (isNSDecl || prefix == "xml") {
				if (preserver == null)
					preserver = new StringWriter ();
				else
					preserver.GetStringBuilder ().Length = 0;
				writer = preserver;

				if (!isNSDecl) {
					is_preserved_xmlns = false;
					preserved_name = localName;
				} else {
					is_preserved_xmlns = true;
					preserved_name = localName == "xmlns" ? 
						String.Empty : localName;
				}
			}

			state = WriteState.Attribute;
		}