First of all you need to add reference to COM library in project.
Add reference to Microsoft word 11.0 word library under COM reference tab Add this in the code behind “using” section

using Microsoft.Office.Interop.Word;
private void CreateWordDocument()
{
// create annonymous object to be referenced throughout
object oMissingReference = System.Reflection.Missing.Value;
object Visible=true;
// define arbitrary starting point for defining range object.
object oStartRange = 0;
object oEndRange = 0;
// create instance of application class
ApplicationClass WordApp = new ApplicationClass();
// create document instance
Document docObject = WordApp.Documents.Add(ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference );
// select a range to add some text/image there
Range rng=docObject.Range(ref oStartRange,ref oMissingReference );
rng.Font.Name=”Arial”;
rng.InsertAfter(”Ashish Sehajpal”);
// create Hyperlink object and assign address, screen tip to it
Object address = @”http://www.sehajpal.com”;
Object screenTip = “Welcome to sehajpal.com”;
// adding Hyperlink to the text “Ashish Sehajpal“
rng.Hyperlinks.Add(rng, ref address, ref oMissingReference , ref screenTip, ref oMissingReference , ref oMissingReference );
// give file name to it so as to save the document
object filename = @”C:\createdbycsharp.doc”;
docObject.SaveAs(ref filename, ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference ,ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference , ref oMissingReference );

WordApp.Visible=true;
}