Creating an XmlNode XmlElement in C without an XmlDocument

Question

I have a simple class that essentially just holds some values  I have overridden the ToString   method to return a nice string representation   Now  I want to create a ToXml   method  that will return something like this    lt Song gt       lt Artist gt Bla lt  Artist gt       lt Title gt Foo lt  Title gt   lt  Song gt    Of course  I could just use a StringBuilder here  but I would like to return an XmlNode or XmlElement  to be used with XmlDocument AppendChild   I do not seem to be able to create an XmlElement other than calling XmlDocument CreateElement  so I wonder if I have just overlooked anything  or if I really either have to pass in either a XmlDocument or ref XmlElement to work with  or have the function return a String that contains the XML I want

User · Accepted Answer

You may want to look at how you can use the built-in features of .NET to serialize and deserialize an object into XML, rather than creating a ToXML() method on every class that is essentially just a Data Transfer Object.

I have used these techniques successfully on a couple of projects but don’t have the implementation details handy right now. I will try to update my answer with my own examples sometime later.

Here's a couple of examples that Google returned:

XML Serialization in .NET by Venkat Subramaniam http://www.agiledeveloper.com/articles/XMLSerialization.pdf

How to Serialize and Deserialize an object into XML http://www.dotnetfunda.com/articles/article98.aspx

Customize your .NET object XML serialization with .NET XML attributes http://blogs.microsoft.co.il/blogs/rotemb/archive/2008/07/27/customize-your-net-object-xml-serialization-with-net-xml-attributes.aspx

User · Answer

You need Linq - System Xml Linq to be precise   You can create XML using XElement from scratch - that should pretty much sort you out

User · Answer

Create a new XmlDocument with the contents you want and then import it into your existing document  by accessing the OwnerDocument property of your existing nodes   XmlNode existing node     of some document  where we don t know necessarily know the XmlDocument    XmlDocument temp   new XmlDocument    temp LoadXml   lt new gt  lt elements  gt  lt  new gt     XmlNode new node   existing node OwnerDocument ImportNode temp DocumentElement  true   existing node AppendChild new node     Good luck

User · Answer

You need Linq - System Xml Linq to be precise   You can create XML using XElement from scratch - that should pretty much sort you out

User · Answer

I would recommend to use XDoc and XElement of System Xml Linq instead of XmlDocument stuff  This would be better and you will be able to make use of the LINQ power in querying and parsing your XML   Using XElement  your ToXml   method will look like the following   public XElement ToXml         XElement element   new XElement  Song                           new XElement  Artist    bla                            new XElement  Title    Foo          return element

User · Answer

I would recommend to use XDoc and XElement of System Xml Linq instead of XmlDocument stuff  This would be better and you will be able to make use of the LINQ power in querying and parsing your XML   Using XElement  your ToXml   method will look like the following   public XElement ToXml         XElement element   new XElement  Song                           new XElement  Artist    bla                            new XElement  Title    Foo          return element

User · Answer

XmlNodes come with an OwnerDocument property   Perhaps you can just do     Node is an XmlNode pulled from an XmlDocument XmlElement e   node OwnerDocument CreateElement  MyNewElement    e InnerText    Some value   node AppendChild e

User · Answer

Another option is to pass a delegate to method  which will create an XmlElement  This way the target method won t get access to whole XmlDocument  but will be able to create new elements

User · Answer

You can t return an XmlElement or an XmlNode  because those objects always and only exist within the context of an owning XmlDocument   XML serialization is a little easier than returning an XElement  because all you have to do is mark properties with attributes and the serializer does all the XML generation for you    Plus you get deserialization for free  assuming you have a parameterless constructor and  well  a bunch of other things    On the other hand  a  you have to create an XmlSerializer to do it  b  dealing with collection properties isn t quite the no-brainer you might like it to be  and c  XML serialization is pretty dumb  you re out of luck if you want to do anything fancy with the XML you re generating     In a lot of cases  those issues don t matter one bit   I for one would rather mark my properties with attributes than write a method

User · Answer

You could return an XmlDocument for the ToXML method in your class  then when you are going to add the Element with the result document just use something like   XmlDocument returnedDocument   Your Class ToXML     XmlDocument finalDocument   new XmlDocument    XmlElement createdElement   finalDocument CreateElement  Desired Element Name    createdElement InnerXML   docResult InnerXML  finalDocument AppendChild createdElement     That way the entire value for  Desired Element Name  on your result XmlDocument will be the entire content of the returned Document   I hope this helps

User · Answer

You can t return an XmlElement or an XmlNode  because those objects always and only exist within the context of an owning XmlDocument   XML serialization is a little easier than returning an XElement  because all you have to do is mark properties with attributes and the serializer does all the XML generation for you    Plus you get deserialization for free  assuming you have a parameterless constructor and  well  a bunch of other things    On the other hand  a  you have to create an XmlSerializer to do it  b  dealing with collection properties isn t quite the no-brainer you might like it to be  and c  XML serialization is pretty dumb  you re out of luck if you want to do anything fancy with the XML you re generating     In a lot of cases  those issues don t matter one bit   I for one would rather mark my properties with attributes than write a method

User · Answer

I would recommend to use XDoc and XElement of System Xml Linq instead of XmlDocument stuff  This would be better and you will be able to make use of the LINQ power in querying and parsing your XML   Using XElement  your ToXml   method will look like the following   public XElement ToXml         XElement element   new XElement  Song                           new XElement  Artist    bla                            new XElement  Title    Foo          return element

User · Answer

XmlNodes come with an OwnerDocument property   Perhaps you can just do     Node is an XmlNode pulled from an XmlDocument XmlElement e   node OwnerDocument CreateElement  MyNewElement    e InnerText    Some value   node AppendChild e

User · Answer

You can t return an XmlElement or an XmlNode  because those objects always and only exist within the context of an owning XmlDocument   XML serialization is a little easier than returning an XElement  because all you have to do is mark properties with attributes and the serializer does all the XML generation for you    Plus you get deserialization for free  assuming you have a parameterless constructor and  well  a bunch of other things    On the other hand  a  you have to create an XmlSerializer to do it  b  dealing with collection properties isn t quite the no-brainer you might like it to be  and c  XML serialization is pretty dumb  you re out of luck if you want to do anything fancy with the XML you re generating     In a lot of cases  those issues don t matter one bit   I for one would rather mark my properties with attributes than write a method

User · Answer

I would recommend to use XDoc and XElement of System Xml Linq instead of XmlDocument stuff  This would be better and you will be able to make use of the LINQ power in querying and parsing your XML   Using XElement  your ToXml   method will look like the following   public XElement ToXml         XElement element   new XElement  Song                           new XElement  Artist    bla                            new XElement  Title    Foo          return element

User · Answer

You need Linq - System Xml Linq to be precise   You can create XML using XElement from scratch - that should pretty much sort you out

User · Answer

From W3C Document Object Model  Core  Level 1 specification  bold is mine       Most of the APIs defined by this   specification are interfaces rather   than classes  That means that an   actual implementation need only expose   methods with the defined names and   specified operation  not actually   implement classes that correspond   directly to the interfaces  This   allows the DOM APIs to be implemented   as a thin veneer on top of legacy   applications with their own data   structures  or on top of newer   applications with different class   hierarchies  This also means that   ordinary constructors  in the Java or   C   sense  cannot be used to create   DOM objects  since the underlying   objects to be constructed may have   little relationship to the DOM   interfaces  The conventional solution   to this in object-oriented design is   to define factory methods that create   instances of objects that implement   the various interfaces  In the DOM   Level 1  objects implementing some   interface  X  are created by a    createX    method on the Document   interface  this is because all DOM   objects live in the context of a   specific Document    AFAIK  you can not create any XmlNode  XmlElement  XmlAttribute  XmlCDataSection  etc  except XmlDocument from a constructor    Moreover  note that you can not use XmlDocument AppendChild   for nodes that are not created via the factory methods of the same document  In case you have a node from another document  you must use XmlDocument ImportNode

User · Answer

Create a new XmlDocument with the contents you want and then import it into your existing document  by accessing the OwnerDocument property of your existing nodes   XmlNode existing node     of some document  where we don t know necessarily know the XmlDocument    XmlDocument temp   new XmlDocument    temp LoadXml   lt new gt  lt elements  gt  lt  new gt     XmlNode new node   existing node OwnerDocument ImportNode temp DocumentElement  true   existing node AppendChild new node     Good luck

User · Answer

You can t return an XmlElement or an XmlNode  because those objects always and only exist within the context of an owning XmlDocument   XML serialization is a little easier than returning an XElement  because all you have to do is mark properties with attributes and the serializer does all the XML generation for you    Plus you get deserialization for free  assuming you have a parameterless constructor and  well  a bunch of other things    On the other hand  a  you have to create an XmlSerializer to do it  b  dealing with collection properties isn t quite the no-brainer you might like it to be  and c  XML serialization is pretty dumb  you re out of luck if you want to do anything fancy with the XML you re generating     In a lot of cases  those issues don t matter one bit   I for one would rather mark my properties with attributes than write a method

User · Answer

You could return an XmlDocument for the ToXML method in your class  then when you are going to add the Element with the result document just use something like   XmlDocument returnedDocument   Your Class ToXML     XmlDocument finalDocument   new XmlDocument    XmlElement createdElement   finalDocument CreateElement  Desired Element Name    createdElement InnerXML   docResult InnerXML  finalDocument AppendChild createdElement     That way the entire value for  Desired Element Name  on your result XmlDocument will be the entire content of the returned Document   I hope this helps

User · Answer

Another option is to pass a delegate to method  which will create an XmlElement  This way the target method won t get access to whole XmlDocument  but will be able to create new elements

User · Answer

XmlDocumnt xdoc   new XmlDocument  XmlNode songNode   xdoc CreateNode XmlNodeType Element   Song   schema  xdoc AppendChild

User · Answer

Why not consider creating your data class es  as just a subclassed XmlDocument  then you get all of that for free  You don t need to serialize or create any off-doc nodes at all  and you get structure you want    If you want to make it more sophisticated  write a base class that is a subclass of XmlDocument  then give it basic accessors  and you re set    Here s a generic type I put together for a project     using System  using System Collections Generic  using System Text  using System Xml  using System IO   namespace FWFWLib       public abstract class ContainerDoc   XmlDocument            protected XmlElement root   null          protected const string XPATH BASE      DATA TYPE            protected const string XPATH SINGLE FIELD      DATA TYPE   FIELD NAME             protected const string DOC DATE FORMAT    yyyyMMdd           protected const string DOC TIME FORMAT    HHmmssfff           protected const string DOC DATE TIME FORMAT   DOC DATE FORMAT   DOC TIME FORMAT           protected readonly string datatypeName    containerDoc           protected readonly string execid   System Guid NewGuid   ToString   Replace   -                   region startup and teardown         public ContainerDoc  string execid  string datatypeName                 root   this DocumentElement              this datatypeName   datatypeName              this execid   execid              if  null    datatypeName          datatypeName Trim                       throw new InvalidDataException   Data type name can not be blank                               Init                       public ContainerDoc  string datatypeName                 root   this DocumentElement              this datatypeName   datatypeName              if  null    datatypeName          datatypeName Trim                       throw new InvalidDataException   Data type name can not be blank                               Init                       private ContainerDoc                        protected virtual void Init                 string basexpath   XPATH BASE Replace    DATA TYPE    datatypeName                root    XmlElement this SelectSingleNode  basexpath                if  null    root                     root   this CreateElement  datatypeName                    this AppendChild  root                              SetFieldValue   createdate   DateTime Now ToString  DOC DATE FORMAT                  SetFieldValue   createtime   DateTime Now ToString  DOC TIME FORMAT                         endregion           region setting getting data fields         public virtual void SetFieldValue  string fieldname  object val                 if  null    fieldname          fieldname Trim                       return                            fieldname   fieldname Replace             ToLower                string xpath   XPATH SINGLE FIELD Replace    FIELD NAME    fieldname   Replace    DATA TYPE    datatypeName                XmlNode node   this SelectSingleNode  xpath                if  null    node                     if  null    val                         node InnerText   val ToString                                    else                   node   this CreateElement  fieldname                    if  null    val                         node InnerText   val ToString                                      root AppendChild  node                                     public virtual string FieldValue  string fieldname                 if  null    fieldname                     fieldname                                 fieldname   fieldname ToLower   Trim                string rtn                   XmlNode node   this SelectSingleNode  XPATH SINGLE FIELD Replace    FIELD NAME    fieldname   Replace    DATA TYPE    datatypeName                  if  null    node                     rtn   node InnerText                            return rtn Trim                       public virtual string ToXml                 return this OuterXml                     public override string ToString                 return ToXml                       endregion           region io         public void WriteTo  string filename                 TextWriter tw   new StreamWriter  filename                tw WriteLine  this OuterXml                tw Close                tw Dispose                       public void WriteTo  Stream strm                 TextWriter tw   new StreamWriter  strm                tw WriteLine  this OuterXml                tw Close                tw Dispose                       public void WriteTo  TextWriter writer                 writer WriteLine  this OuterXml                       endregion

User · Answer

From W3C Document Object Model  Core  Level 1 specification  bold is mine       Most of the APIs defined by this   specification are interfaces rather   than classes  That means that an   actual implementation need only expose   methods with the defined names and   specified operation  not actually   implement classes that correspond   directly to the interfaces  This   allows the DOM APIs to be implemented   as a thin veneer on top of legacy   applications with their own data   structures  or on top of newer   applications with different class   hierarchies  This also means that   ordinary constructors  in the Java or   C   sense  cannot be used to create   DOM objects  since the underlying   objects to be constructed may have   little relationship to the DOM   interfaces  The conventional solution   to this in object-oriented design is   to define factory methods that create   instances of objects that implement   the various interfaces  In the DOM   Level 1  objects implementing some   interface  X  are created by a    createX    method on the Document   interface  this is because all DOM   objects live in the context of a   specific Document    AFAIK  you can not create any XmlNode  XmlElement  XmlAttribute  XmlCDataSection  etc  except XmlDocument from a constructor    Moreover  note that you can not use XmlDocument AppendChild   for nodes that are not created via the factory methods of the same document  In case you have a node from another document  you must use XmlDocument ImportNode

User · Answer

You need Linq - System Xml Linq to be precise   You can create XML using XElement from scratch - that should pretty much sort you out

User · Answer

Why not consider creating your data class es  as just a subclassed XmlDocument  then you get all of that for free  You don t need to serialize or create any off-doc nodes at all  and you get structure you want    If you want to make it more sophisticated  write a base class that is a subclass of XmlDocument  then give it basic accessors  and you re set    Here s a generic type I put together for a project     using System  using System Collections Generic  using System Text  using System Xml  using System IO   namespace FWFWLib       public abstract class ContainerDoc   XmlDocument            protected XmlElement root   null          protected const string XPATH BASE      DATA TYPE            protected const string XPATH SINGLE FIELD      DATA TYPE   FIELD NAME             protected const string DOC DATE FORMAT    yyyyMMdd           protected const string DOC TIME FORMAT    HHmmssfff           protected const string DOC DATE TIME FORMAT   DOC DATE FORMAT   DOC TIME FORMAT           protected readonly string datatypeName    containerDoc           protected readonly string execid   System Guid NewGuid   ToString   Replace   -                   region startup and teardown         public ContainerDoc  string execid  string datatypeName                 root   this DocumentElement              this datatypeName   datatypeName              this execid   execid              if  null    datatypeName          datatypeName Trim                       throw new InvalidDataException   Data type name can not be blank                               Init                       public ContainerDoc  string datatypeName                 root   this DocumentElement              this datatypeName   datatypeName              if  null    datatypeName          datatypeName Trim                       throw new InvalidDataException   Data type name can not be blank                               Init                       private ContainerDoc                        protected virtual void Init                 string basexpath   XPATH BASE Replace    DATA TYPE    datatypeName                root    XmlElement this SelectSingleNode  basexpath                if  null    root                     root   this CreateElement  datatypeName                    this AppendChild  root                              SetFieldValue   createdate   DateTime Now ToString  DOC DATE FORMAT                  SetFieldValue   createtime   DateTime Now ToString  DOC TIME FORMAT                         endregion           region setting getting data fields         public virtual void SetFieldValue  string fieldname  object val                 if  null    fieldname          fieldname Trim                       return                            fieldname   fieldname Replace             ToLower                string xpath   XPATH SINGLE FIELD Replace    FIELD NAME    fieldname   Replace    DATA TYPE    datatypeName                XmlNode node   this SelectSingleNode  xpath                if  null    node                     if  null    val                         node InnerText   val ToString                                    else                   node   this CreateElement  fieldname                    if  null    val                         node InnerText   val ToString                                      root AppendChild  node                                     public virtual string FieldValue  string fieldname                 if  null    fieldname                     fieldname                                 fieldname   fieldname ToLower   Trim                string rtn                   XmlNode node   this SelectSingleNode  XPATH SINGLE FIELD Replace    FIELD NAME    fieldname   Replace    DATA TYPE    datatypeName                  if  null    node                     rtn   node InnerText                            return rtn Trim                       public virtual string ToXml                 return this OuterXml                     public override string ToString                 return ToXml                       endregion           region io         public void WriteTo  string filename                 TextWriter tw   new StreamWriter  filename                tw WriteLine  this OuterXml                tw Close                tw Dispose                       public void WriteTo  Stream strm                 TextWriter tw   new StreamWriter  strm                tw WriteLine  this OuterXml                tw Close                tw Dispose                       public void WriteTo  TextWriter writer                 writer WriteLine  this OuterXml                       endregion

User · Answer

From W3C Document Object Model  Core  Level 1 specification  bold is mine       Most of the APIs defined by this   specification are interfaces rather   than classes  That means that an   actual implementation need only expose   methods with the defined names and   specified operation  not actually   implement classes that correspond   directly to the interfaces  This   allows the DOM APIs to be implemented   as a thin veneer on top of legacy   applications with their own data   structures  or on top of newer   applications with different class   hierarchies  This also means that   ordinary constructors  in the Java or   C   sense  cannot be used to create   DOM objects  since the underlying   objects to be constructed may have   little relationship to the DOM   interfaces  The conventional solution   to this in object-oriented design is   to define factory methods that create   instances of objects that implement   the various interfaces  In the DOM   Level 1  objects implementing some   interface  X  are created by a    createX    method on the Document   interface  this is because all DOM   objects live in the context of a   specific Document    AFAIK  you can not create any XmlNode  XmlElement  XmlAttribute  XmlCDataSection  etc  except XmlDocument from a constructor    Moreover  note that you can not use XmlDocument AppendChild   for nodes that are not created via the factory methods of the same document  In case you have a node from another document  you must use XmlDocument ImportNode

User · Answer

XmlDocumnt xdoc   new XmlDocument  XmlNode songNode   xdoc CreateNode XmlNodeType Element   Song   schema  xdoc AppendChild

User · Answer

From W3C Document Object Model  Core  Level 1 specification  bold is mine       Most of the APIs defined by this   specification are interfaces rather   than classes  That means that an   actual implementation need only expose   methods with the defined names and   specified operation  not actually   implement classes that correspond   directly to the interfaces  This   allows the DOM APIs to be implemented   as a thin veneer on top of legacy   applications with their own data   structures  or on top of newer   applications with different class   hierarchies  This also means that   ordinary constructors  in the Java or   C   sense  cannot be used to create   DOM objects  since the underlying   objects to be constructed may have   little relationship to the DOM   interfaces  The conventional solution   to this in object-oriented design is   to define factory methods that create   instances of objects that implement   the various interfaces  In the DOM   Level 1  objects implementing some   interface  X  are created by a    createX    method on the Document   interface  this is because all DOM   objects live in the context of a   specific Document    AFAIK  you can not create any XmlNode  XmlElement  XmlAttribute  XmlCDataSection  etc  except XmlDocument from a constructor    Moreover  note that you can not use XmlDocument AppendChild   for nodes that are not created via the factory methods of the same document  In case you have a node from another document  you must use XmlDocument ImportNode

[c#] Creating an XmlNode/XmlElement in C# without an XmlDocument?

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