how to replace string with image in word document

See more:

C#

C#4.0

How to replace string in word document with image

I have tried like this

foreach (Word.Range docRange in docTemp.Words)
                {

                    if (docRange.Text.Trim().Equals("signature",
                       StringComparison.CurrentCultureIgnoreCase))
                    {
                        string signaturePath = Properties.Settings.Default.SFolderPath + "\\Signatures\\signature.png";
                        Word.InlineShape pic = docRange.InlineShapes.AddPicture(signaturePath);

                        
                   }
                }

but its inserting image not replacing string "signature".