PM> Install-Package Spire.Doc

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

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

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

            //Find all matching text in the document
            TextSelection[] text = document.FindAllString("transcendentalism", false, true);

            //Loop through all matching text and set highlight color for them
            foreach (TextSelection seletion in text)
            {
                seletion.GetAsOneRange().CharacterFormat.HighlightColor = Color.Yellow;
            }

            //Save the result file
            document.SaveToFile("FindHighlight.docx", FileFormat.Docx);
        }
    }
}

Imports Spire.Doc
Imports Spire.Doc.Documents

Namespace FindHighlight
    Class Program
        Private Shared Sub Main(ByVal args() As String)

            'Create a Document instance
            Dim document As Document = New Document

            'Load a sample Word document 
            document.LoadFromFile("input.docx")

            'Find all matching text in the document
            Dim text() As TextSelection = document.FindAllString("transcendentalism", False, True)

            'Loop through all matching text and set highlight color for them
            For Each seletion As TextSelection In text
                seletion.GetAsOneRange.CharacterFormat.HighlightColor = Color.Yellow
            Next

            'Save the result file
            document.SaveToFile("FindHighlight.docx", FileFormat.Docx)
        End Sub
    End Class
End Namespace

PM> Install-Package Spire.Doc

using Spire.Doc;
using Spire.Doc.Documents;
using System.Text;
using System.IO;

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

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

            //Create a StringBuilder instance
            StringBuilder sb = new StringBuilder();

            //Extract text from Word and save to StringBuilder instance
            foreach (Section section in document.Sections)
            {
                foreach (Paragraph paragraph in section.Paragraphs)
                {
                    sb.AppendLine(paragraph.Text);
                }
            }

            //Create a new txt file to save the extracted text
            File.WriteAllText("Extract.txt", sb.ToString());
        }
    }
}

Imports Spire.Doc
Imports Spire.Doc.Documents
Imports System.Text
Imports System.IO

Namespace ExtractTextfromWord
    Class ExtractText
        Private Shared Sub Main(ByVal args() As String)

            'Create a Document instance
            Dim document As Document = New Document

            'Load a sample Word document 
            document.LoadFromFile("input.docx")

            'Create a StringBuilder instance
            Dim sb As StringBuilder = New StringBuilder

            'Extract text from Word and save to StringBuilder instance
            For Each section As Section In document.Sections
                For Each paragraph As Paragraph In section.Paragraphs
                    sb.AppendLine(paragraph.Text)
                Next
            Next

            'Create a new txt file to save the extracted text
            File.WriteAllText("Extract.txt", sb.ToString)
        End Sub
    End Class
End Namespace

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

namespace ExtractImage
{
    class Program
    {
        static void Main(string[] args)
        {
            //Load a Word document
            Document document = new Document("input.docx");
            int index = 0;

            //Get each section of document
            foreach (Section section in document.Sections)
            {
                //Get each paragraph of section
                foreach (Paragraph paragraph in section.Paragraphs)
                {
                    //Get each document object of a specific paragraph
                    foreach (DocumentObject docObject in paragraph.ChildObjects)
                    {
                        //If the DocumentObjectType is picture, save it out of the document
                        if (docObject.DocumentObjectType == DocumentObjectType.Picture)
                        {
                            DocPicture picture = docObject as DocPicture;
                            picture.Image.Save(string.Format("image_{0}.png", index), System.Drawing.Imaging.ImageFormat.Png);
                            index++;
                        }
                    }
                }
            }
        }
    }
}

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

Namespace ExtractImage
    
    Class Program
        
        Private Shared Sub Main(ByVal args() As String)

            'Load a Word document
            Dim document As Document = New Document("input.docx")
            Dim index As Integer = 0

            'Get each section of document
            For Each section As Section In document.Sections

                'Get each paragraph of section
                For Each paragraph As Paragraph In section.Paragraphs

                    'Get each document object of a specific paragraph
                    For Each docObject As DocumentObject In paragraph.ChildObjects

                        'If the DocumentObjectType is picture, save it out of the document
                        If (docObject.DocumentObjectType = DocumentObjectType.Picture) Then
                            Dim picture As DocPicture = CType(docObject,DocPicture)
                            picture.Image.Save(String.Format("image_{0}.png", index), System.Drawing.Imaging.ImageFormat.Png)
                            index = (index + 1)
                        End If
                        
                    Next
                Next
            Next
        End Sub
    End Class
End Namespace

PM> Install-Package Spire.Doc

using Spire.Doc;

namespace ReplaceAllText
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Instantiate an object of the Document class
            Document document = new Document();
            //Load a sample Word document
            document.LoadFromFile("Sample.docx");

            //Replace all instances of specific text with new text
            document.Replace("Spire.Doc", "Eiceblue", false, true);

            //Save the result document
            document.SaveToFile("ReplaceAllText.docx", FileFormat.Docx2016);
            document.Close();
        }
    }
}

using Spire.Doc;

namespace ReplaceFirstText
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Instantiate an object of the Document class
            Document document = new Document();
            //Load a sample Word document
            document.LoadFromFile("Sample.docx");

            //Change the text replacement mode to replace the first instance only
            document.ReplaceFirst = true;

            //Replace the first instance of specific text with new text
            document.Replace("Spire.Doc", "Eiceblue", false, true);

            //Save the result document
            document.SaveToFile("ReplaceFirstText.docx", FileFormat.Docx2016);
            document.Close();
        }
    }
}

using Spire.Doc;
using Spire.Doc.Documents;
using Spire.Doc.Fields;

namespace ReplaceTextWithImage
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Instantiate an object of the Document class
            Document document = new Document();
            //Load a sample Word document
            document.LoadFromFile("Sample.docx");

            //Find specific text in the document
            TextSelection[] selections = document.FindAllString("Spire.Doc", true, true);

            int index = 0;
            Paragraph ownerParagraph = null;

            //Loop through the matched text
            foreach (TextSelection selection in selections)
            {
                //Get the paragraph where the text is located
                ownerParagraph = selection.GetAsOneRange().OwnerParagraph;

                //Get the index position of the text in the paragraph
                index = ownerParagraph.ChildObjects.IndexOf(selection.GetAsOneRange());

                //Load an image
                DocPicture pic = new DocPicture(document);
                pic.LoadImage("img.png");

                //Insert the image into the paragraph at the index position of the text
                ownerParagraph.ChildObjects.Insert(index, pic);

                //Remove the text from the paragraph
                ownerParagraph.ChildObjects.Remove(selection.GetAsOneRange());
            }

            //Save the result document
            document.SaveToFile("ReplaceTextWithImage.docx", FileFormat.Docx2016);
            document.Close();
        }
    }
}

using Spire.Doc;
using System.Text.RegularExpressions;

namespace ReplaceTextWithRegex
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Instantiate an object of the Document class
            Document document = new Document();
            //Load a sample Word document
            document.LoadFromFile("Sample.docx");

            //Create a regex to match the text that starts with #
            Regex regex = new Regex(@"\#\w+\b");

            //Replace the matched text with new text
            document.Replace(regex, "Spire.Doc");

            //Save the result document
            document.SaveToFile("ReplaceTextWithRegex.docx", FileFormat.Docx2016);
            document.Close();
        }
    }
}

using Spire.Doc;
using Spire.Doc.Interface;

namespace ReplaceTextWithDocument
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Instantiate an object of the Document class
            Document document = new Document();
            //Load a sample Word document
            document.LoadFromFile("Template.docx");

            //Load another Word document
            IDocument document1 = new Document("Report.docx");

            //Replace specific text in the sample document with content from another document
            document.Replace("Annual Sales", document1, false, true);

            //Save the result document
            document.SaveToFile("ReplaceTextWithDocument.docx", FileFormat.Docx2016);
            document.Close();
        }
    }
}