Docusign C# SDK , Update "Sender Field Data" created them from a template that was also created MS Word DocuSign Add-on

Following this instruction : https://support.docusign.com/s/document-item?language=en_US&bundleId=als1679428547895&topicId=kyy1679958874136.html&_LANG=enus

I was able to create a word document using DocuSign Add-on , and then uploaded to Docusign as template.

In MS Word it looks like this :

I created an app in C# that uses DocuSign.eSign.dll 8.0.2 version and cannot set values to those "sender field data".

Any idea how to do it ?

These is what I tried so far : 

1. Tried upgrading the library to 8.6.0 to use :
   envelopeDefinition.PrefillTabs (failed)

2. using TextCustomField like this (failed) :

   envelopeDefinition.CustomFields = new CustomFields
   {
       TextCustomFields = new List<TextCustomField>
       {
           new TextCustomField
           {
               Name = "EventName", // Field name WITHOUT braces
               Required = "false",
               Show = "true",
               Value = "PARTY"
           }
       }
   };

3. using CompositeTemplates (Failed) : 

4. envelopeDefinition.CompositeTemplates = new List<CompositeTemplate>
   {
   	new CompositeTemplate
   	{
   		ServerTemplates = new List<ServerTemplate>
   		{
   			new ServerTemplate
   			{
   				Sequence = "1",
   				TemplateId = templateId // Your existing template
   			}
   		},
   		Document = new Document
   		{
   			DocumentId = "1",
   			Name = "Document Form",
   			DocumentBase64 = null, // Don't need to upload - using template doc
   			DocGenFormFields = new List<DocGenFormField>
   			{
   				new DocGenFormField { Name = "EventName", Value = "BIG TITLE HEADER 2026" },
   				new DocGenFormField { Name = "EventVenueAddress", Value = "ABC DE EF****" },
   				new DocGenFormField { Name = "ProxyHolderName", Value = "123 45 EF****" },
   				new DocGenFormField { Name = "EventDate", Value = "February 1 2026" }
   			}
   		}
   	}
   };

    

Any idea ? I cannot find any good solution so far !!