How to: Insert Dynamic Content

• Feb 17, 2023
• 3 minutes to read

The code sample below shows how use the DOCVARIABLE field and RichEditControl.CalculateDocumentVariable event to insert dynamic (formatted) content. In this example, the DOCVARIABLE field is used to display the DevExpress community website’s RSS feed.

Note

A complete sample project is available at Dynamic Content demo module.

1. Load a document template, if required.

2. Insert a DOCVARIABLE field. Use the FieldCollection.Create method, as shown below:

   C#

   private static void InsertDocVariableField(Document document)
   {
       document.Fields.Create(document.Range.End, "DOCVARIABLE rssFeed");
   }
   

   VB.NET

   Private Shared Sub InsertDocVariableField(ByVal document As Document)
   document.Fields.Create(document.Range.[End], "DOCVARIABLE rssFeed")
   End Sub
   

3. Use the RichEditDocumentServer object to generate or load the target dynamic content. In this example, the GenerateRssFeed method returns this RichEditDocumentServer object.

   C#

   private static RichEditDocumentServer GenerateRssFeed()
   {
       RichEditDocumentServer rssProcessor = new RichEditDocumentServer();
       Document document = rssProcessor.Document;
   
       //Create a new bulleted list
       AbstractNumberingList abstractNumberingList = document.AbstractNumberingLists.BulletedListTemplate.CreateNew();
       document.NumberingLists.CreateNew(abstractNumberingList.Index);
   
       SyndicationFeed feed = null;
   
       //Extract feed items
       try
       {
           using (XmlReader reader = XmlReader.Create("https://community.devexpress.com/blogs/MainFeed.aspx"))
           {
               feed = SyndicationFeed.Load(reader);
           }
       }
       catch
       {
           return null;
       }
   
       //Format each feed item into the bullet list item
       document.BeginUpdate();
       foreach (SyndicationItem item in feed.Items)
           //This method inserts each item as a hyperlink with publication date
           AddSyndicationItem(document, item);
       document.EndUpdate();
       return rssProcessor;
   }
   

   VB.NET

   Private Shared Function GenerateRssFeed() As RichEditDocumentServer
   Dim rssProcessor As RichEditDocumentServer = New RichEditDocumentServer()
   Dim document As Document = rssProcessor.Document
   
   'Create a new bulleted list
   Dim abstractNumberingList As AbstractNumberingList = document.AbstractNumberingLists.BulletedListTemplate.CreateNew()
   document.NumberingLists.CreateNew(abstractNumberingList.Index)
   Dim feed As SyndicationFeed = Nothing
   
   ' Extract feed items
   Try
   
       Using reader As XmlReader = XmlReader.Create("https://community.devexpress.com/blogs/MainFeed.aspx")
           feed = SyndicationFeed.Load(reader)
       End Using
   
   Catch
       Return Nothing
   End Try
   
   document.BeginUpdate()
   
   ' Format each feed item into the bullet list item
   For Each item As SyndicationItem In feed.Items
       'This method inserts each item as a hyperlink with publication date
       AddSyndicationItem(document, item)
   Next
   
   document.EndUpdate()
   Return rssProcessor
   End Function
   

4. Handle the RichEditControl.CalculateDocumentVariable event. Use the RichEditDocumentServer object created in the previous step as the CalculateDocumentVariableEventArgs.Value property value. Identify the field by the CalculateDocumentVariableEventArgs.VariableName property value.

   Note

   The current DOCVARIABLE field value may be lost if you update this field in another word processing application, where the CalculateDocumentVariable event isn’t used. Use one of the following approaches to suppress DOCVARIABLE field updates:

   • Set the CalculateDocumentVariableEventArgs.FieldLocked property to true in the CalculateDocumentVariable event handler.
   • Replace document fields with their values.
   C#

   void richEditControl_CalculateDocumentVariable(object sender, CalculateDocumentVariableEventArgs e)
   {
       //Retrieve the field by its ID
       if (e.VariableName == "rssFeed")
       {
           //Retain the last paragraph of the inserted document in the resulting document
           e.KeepLastParagraph = true;
   
           //Use the method result as the field's value
           e.Value = GenerateRssFeed();
           if (e.Value != null)
   
               //Keep the current field value
               e.Handled = true;
   
               //Suppress the field update
               e.FieldLocked = true;
       }
   
   }
   

   VB.NET

   Private Sub WordProcessor_CalculateDocumentVariable(ByVal sender As Object, ByVal e As CalculateDocumentVariableEventArgs)
   
       'Retrieve the field by its ID
       If e.VariableName = "rssFeed" Then
   
           'Retain the last paragraph of the inserted document in the resulting document
           e.KeepLastParagraph = True
   
           'Use the method result as the field's value
           e.Value = GenerateRssFeed()
   
           'Keep the current field value
           If e.Value IsNot Nothing Then
           e.Handled = True
   
           'Suppress the field update
           e.FieldLocked = True
       End If
   End Sub
   

5. Call the FieldCollection.Update to update all document fields.

   C#

   public DynamicContentModule()
   {
       //This method specifies security protocols for RSS feed
       SetupSecurityProtocol();
   
       //Load a document template
       richEditControl.LoadDocument("Dynamic Content.docx");
   
       //Insert the DOCVARIABLE field
       InsertDocVariableField(richEditControl.Document);
   
       //Subscribe to the CalculateDocumentVariable event
       richEditControl.CalculateDocumentVariable += richEditControl_CalculateDocumentVariable;
   
       //Update all document fields
       richEditControl.Document.Fields.Update();
   }
   

   VB.NET

   Public Sub New()
   
   'This method specifies security protocols for RSS feed
       SetupSecurityProtocol()
   
      'Load a document template
       richEditControl.LoadDocument("Dynamic Content.docx")
       InsertDocVariableField(richEditControl.Document)
   
       'Subscribe to the CalculateDocumentVariable event
       richEditControl.CalculateDocumentVariable += richEditControl_CalculateDocumentVariable
   
       'Update all document fields
       richEditControl.Document.Fields.Update()
   End Sub