import com.spire.doc.Document;
import com.spire.doc.FileFormat;

import java.text.SimpleDateFormat;
import java.util.ArrayList;

public class MailMargeDemo {

     public void mailMerge(String docFile, String resultFilePath) throws Exception {
        Document doc = new Document();
        doc.loadFromFile(docFile);

        SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");
        Calendar calendar=Calendar.getInstance();

        ArrayList dateList=new ArrayList<>();
        int []offset={-5,5,6,-2,2};
        for(int data:offset){
            calendar.setTime(new Date());
            calendar.add(Calendar.YEAR,data);
            dateList.add(format.format(calendar.getTime()));
        }
        String[] values =new String[dateList.size()];
        dateList.toArray(values);
        
        String []fields={
                "SubGrantPAStartDateValue",
                "SubGrantPAEndDateValue",
                "SubGrantPAExtensionDateValue",
                "SubGrantPSStartDateValue",
                "SubGrantPSEndDateValue"
        };
        doc.getMailMerge().execute(fields,values);
        doc.saveToFile(resultFilePath, FileFormat.Docx);
    }
}

using System;
using Spire.Doc;

namespace DemoOnlineCode
{
    class MailMerge
    {
        public void demoMailMerge(String docFile)
        {
            Document document = new Document(docFile, FileFormat.Auto);

            string[] values = {
                                  DateTime.Today.AddYears(-5).ToString("yyyy-MM-dd"),
                                  DateTime.Today.AddYears(5).ToString("yyyy-MM-dd"),
                                  DateTime.Today.AddYears(6).ToString("yyyy-MM-dd"),
                                  DateTime.Today.AddYears(-2).ToString("yyyy-MM-dd"),
                                  DateTime.Today.AddYears(2).ToString("yyyy-MM-dd")
                              };
            string[] fields = {
                                   "SubGrantPAStartDateValue",
                                   "SubGrantPAEndDateValue",
                                   "SubGrantPAExtensionDateValue",
                                   "SubGrantPSStartDateValue",
                                   "SubGrantPSEndDateValue"
                                 };
            document.MailMerge.Execute(fields, values);
            document.SaveToFile("demo.doc", FileFormat.Doc);

        }
    }
}