Update text node methods

Author: FreePhoenix888

csharp/Platform.Data.Doublets.Xml/DefaultXmlStorage.cs

@@ -539,15 +539,20 @@ public TLinkAddress CreateTextNode(string text)
             return Links.GetOrCreate(TextNodeType, contentLink);
         }
 
-        public string GetTextNodeValue(TLinkAddress textNodeLinkAddress)
+        public void EnsureIsTextNode(TLinkAddress possibleTextNodeLinkAddress)
         {
-            var textNodeType = Links.GetSource(textNodeLinkAddress);
-            if (!EqualityComparer.Equals(textNodeType, TextNodeType))
+            if(!IsTextNode(possibleTextNodeLinkAddress))
             {
-                throw new Exception("The passed link address is not a text element link address.");
+                throw new ArgumentException($"{possibleTextNodeLinkAddress} is not a text node link address");
             }
+        }
+      
+        
+        public string GetTextNode(TLinkAddress textNodeLinkAddress)
+        {
+            EnsureIsTextNode(textNodeLinkAddress);
             var contentLink = Links.GetTarget(textNodeLinkAddress);
-            return UnicodeSequenceToStringConverter.Convert(contentLink);
+            return GetString(contentLink);
         }
 
         #endregion

csharp/Platform.Data.Doublets.Xml/XmlExporter.cs

@@ -55,7 +55,7 @@ public void ExportNode(XmlWriter xmlWriter, TLinkAddress nodeLinkAddress)
             }
             else
             {
-                throw new ArgumentException("The passed link address is not a text, attribute or element.", nameof(nodeLinkAddress));
+                throw new ArgumentException("The passed link address is not a node.", nameof(nodeLinkAddress));
             }
         }
 
@@ -79,7 +79,7 @@ private void ExportAttributeNode(XmlWriter xmlWriter, TLinkAddress xmlNodeLinkAd
 
         public void ExportTextNode(XmlWriter xmlWriter, TLinkAddress textNodeLinkAddress)
         {
-            var text = _storage.GetTextNodeValue(textNodeLinkAddress);
+            var text = _storage.GetTextNode(textNodeLinkAddress);
             xmlWriter.WriteString(text);
         }
     }