How to Remove the Instructions Text in word in VSTO

Question

I strucked from the morning. please anyone help me.

 

here is my code.

 

Microsoft.Office.Interop.Word.Application app = Globals.ThisAddIn.Application;

Microsoft.Office.Interop.Word.Document doc1 = app.ActiveDocument;

Selection wordSelection = Globals.ThisAddIn.Application.Selection;

wordSelection.HomeKey(WdUnits.wdStory);

doc1.Content.Find.ClearFormatting();

doc1.Content.Find.Replacement.ClearFormatting();

doc1.Content.Find.set_Style(doc1.Styles["Instructions"]);

doc1.Content.Find.Text = "";

doc1.Content.Find.Replacement.Text = "";

doc1.Content.Find.Forward = true;

bInstructions = doc1.Content.Find.Execute(WdReplace.wdReplaceAll);