AliasNamespaceDictionary NamespaceAliases
  Property NameNamespaceAliases  
  Property Type string  
  Accessors Read Only  
  DescriptionA collection of name value pairs, containing a namespace URI and namespace Alias.  

These alias will be declared at the root level in the document.
The sample shows what you get if an alias “MyAlias”, and UIR "http://sample" are added to the collection.

<?xml version="1.0"?>
<MyAlias:Customer xmlns:MyAlias="http://sample"

Also See CNamespaceAliasMap

public class AliasNamespaceDictionary : CollectionBase
    public String this[ String nsAlias ]
        get ;
        set ;
    public void Add( String nsAlias, String namespaceUri ) ;
    public bool Contains( String nsAlias ) ;
    public void Remove( String nsAlias ) ;