操作XmlDocument时，出现"System.OutOfMemoryException"异常，如何解决加载大数据的情况？

System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
at System.String.GetStringForStringBuilder(String value, Int32 startIndex, Int32 length, Int32 capacity)
at System.Text.StringBuilder.GetNewString(String currentString, Int32 requiredLength)
at System.Text.StringBuilder.Append(String value)
at System.IO.StringWriter.Write(String value)
at System.Xml.XmlTextEncoder.Write(String text)