public void placeActiveView()
		
		{
			
			UIDocument uidoc = this.ActiveUIDocument;
			Document doc = uidoc.Document;
			
			View activeView = doc.ActiveView;
			
			using(var form = new Form1())
			{
				//use ShowDialog to show the form as a modal dialog box. 
	    		form.ShowDialog();
	    
	    		//if the user hits cancel just drop out of macro
	    		if(form.DialogResult == forms.DialogResult.Cancel) return;
	    		
	    		//create a new variable to store the user input text
	    		string sheetNumber = form.textString.ToString();
				
				
				ViewSheet viewSh = null;
				
				FilteredElementCollector sheets = new FilteredElementCollector(doc).OfClass(typeof(ViewSheet));
				
				foreach (ViewSheet sht in sheets)
	            
				{
					if (sht.SheetNumber.ToString() == sheetNumber) //find the sheet that matches the user input text
	                	viewSh = sht;
	            }
				
				//TaskDialog.Show("out","Selected sheet Id: " + viewSh.Id.ToString());
				
				using (Transaction t = new Transaction(doc))
					
					{
					
						t.Start("Add view to sheet");
						
							try
						{															
							Viewport vp = Viewport.Create(doc, viewSh.Id, activeView.Id, new XYZ(0,0,0));
							
							t.Commit();
						}
													
			/*
							catch (System.NullReferenceException ex)
						{
							TaskDialog.Show("Exception Caught", "The Sheet Number does not exists");
							t.RollBack();
							placeActiveView();
						}

			
					*/		catch 
						{
								if (sheetNumber == ""){
								TaskDialog.Show("Warning","Please enter a sheet number");
                    			//t.RollBack();
                    			placeActiveView();
								}
								
								else if (viewSh == null){
								TaskDialog.Show("Warning","The sheet number does not exist");
								t.RollBack();
								placeActiveView();
								}
					
								else {
								TaskDialog.Show("Warning","The view is already placed on another sheet");
								t.RollBack();
								placeActiveView();
								}
							}
							
							
					//close using
					}
			//close Form1
			}
		//close placeActiveView	
		}