The DataSet.ReadXml(System.Xml.XmlReader) method provides a way to read either data only, or both data and schema into a System.Data.DataSet from an XML document, whereas the DataSet.ReadXmlSchema(System.Xml.XmlReader) method reads only the schema. To read both data and schema, use one of the ReadXML overloads that includes the mode parameter, and set its value to ReadSchema.

Note that the same is true for the DataSet.WriteXml(System.IO.Stream) and DataSet.WriteXmlSchema(System.IO.Stream) methods, respectively. To write XML data, or both schema and data from the DataSet, use the WriteXml method. To write just the schema, use the WriteXmlSchema method.

If an in-line schema is specified, the in-line schema is used to extend the existing relational structure prior to loading the data. If there are any conflicts (for example, the same column in the same table defined with different data types) an exception is raised.

If no in-line schema is specified, the relational structure is extended through inference, as necessary, according to the structure of the XML document. If the schema cannot be extended through inference in order to expose all data, an exception is raised.

If the XML Schema for a System.Data.DataSet includes a targetNamespace, data may not be read, and you may encounter exceptions when calling DataSet.ReadXml(System.Xml.XmlReader) to load the System.Data.DataSet with XML that contains elements with no qualifying namespace. To read unqualified elements, set elementFormDefault equal to "qualified" in your XML Schema as the following example demonstrates.

 <xsd:schema id="MyDataSet" 
    elementFormDefault="qualified" 
    targetNamespace="http://www.tempuri.org/MyDataSet.xsd" 
    xmlns="http://www.tempuri.org/MyDataSet.xsd" 
    xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
    xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
 </xsd:schema>

System.Xml.XmlTextReader inherits from System.Xml.XmlReader.