PM> Install-Package Spire.Doc

using Spire.Doc;

namespace ConvertToRtf
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Word document instance
            Document document = new Document();

            //Load a Word sample document
            document.LoadFromFile("sample.docx");

            // Save the document to RTF
            document.SaveToFile("Result.rtf", FileFormat.Rtf);
        }

    }
}

Imports Spire.Doc

Namespace ConvertToRtf
    
    Class Program
        
        Private Shared Sub Main(ByVal args() As String)
            'Create a Word document instance
            Dim document As Document = New Document
            'Load a Word sample document
            document.LoadFromFile("sample.docx")
            'Save the document to RTF
            document.SaveToFile("Result.rtf", FileFormat.Rtf)
        End Sub
    End Class
End Namespace

using Spire.Doc;
using System;

public class RtfToDocDocx
{

    public static void Main(String[] args)
    {
        // Create a Document instance
        Document document = new Document();
        // Load an RTF document
        document.LoadFromFile("input.rtf", FileFormat.Rtf);
        // Save the document to Doc
        document.SaveToFile("toDoc.doc", FileFormat.Doc);
        // Save the document to Docx
        document.SaveToFile("toDocx.docx", FileFormat.Docx2013);
    }
}

Imports Spire.Doc
Imports System
Public Class RtfToDocDocx
    
    Public Shared Sub Main(ByVal args() As String)
        ' Create a Document instance
        Dim document As Document = New Document
        ' Load an RTF document
        document.LoadFromFile("input.rtf", FileFormat.Rtf)
        ' Save the document to Doc
        document.SaveToFile("toDoc.doc", FileFormat.Doc)
        ' Save the document to Docx
        document.SaveToFile("toDocx.docx", FileFormat.Docx2013)
    End Sub
End Class

PM> Install-Package Spire.Doc

using Spire.Doc;
using System;

namespace DocExample
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Create a Document class instance
            Document document = new Document();

            //Load an OpenXML file from disk
            document.LoadFromFile(@"C:\Samples\Sample.xml", FileFormat.Xml);

            //Convert the OpenXML file to a Word document and save it
            document.SaveToFile("OpenXMLToWord.docx", FileFormat.Docx2013);
        }
    }
}

Imports System
Imports Spire.Doc

Module Program
    Sub Main(args As String())
        'Create a Document class instance
        Dim document As New Document()

        'Load an OpenXML file from disk
        document.LoadFromFile("C:\Samples\Sample.xml", FileFormat.Xml)

        'Convert the OpenXML file to a Word document and save it
        document.SaveToFile("OpenXMLToWord.docx", FileFormat.Docx2013)
    End Sub
End Module

using Spire.Doc;
using System;

namespace DocExample
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Create a Document class instance
            Document document = new Document();

            //Load a Word document from disk
            document.LoadFromFile(@"C:\Samples\Sample.docx");

            //Convert the Word document to an OpenXML file and save it
            //Change WordXML to WordML to convert to ML file
            document.SaveToFile("WordToOpenXMl.xml", FileFormat.WordXml);
        }
    }
}

Imports System
Imports Spire.Doc

Module Program
    Sub Main(args As String())
        'Create a Document class instance
        Dim document As New Document()

        'Load a Word document from disk
        document.LoadFromFile("C:\Samples\Sample.docx")

        'Convert the Word document to an OpenXML file and save it
        'Change WordXML to WordML to convert to ML file
        document.SaveToFile("WordToOpenXML.xml", FileFormat.WordXml)
    End Sub
End Module

PM> Install-Package Spire.Doc

using System;
using Spire.Doc;
using Spire.Doc.Documents;

namespace ConvertHTMLtoWord
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Create an instance of Document
            Document document = new Document();

            //Load an HTML file form disk
            document.LoadFromFile(@"D:\testp\test.html");
            

            //Save the HTML file as Word
            String result = "HtmltoWord.docx";
            document.SaveToFile(result, FileFormat.Docx2013);
        }
   }
}

Imports System
Imports Spire.Doc
Imports Spire.Doc.Documents

Module Program
    Sub Main(args As String())
        'Create an instance of Document
        Dim document As New Document()

        'Load an HTML file form disk
        document.LoadFromFile("D:\testp\test.html")

        'Save the HTML file as Word
        Dim result As String = "HtmltoWord.docx"
        document.SaveToFile(result, FileFormat.Docx2013)
    End Sub
End Module