مشكله فى اضافة Div داخل Gridview

بسم الله الرحمن الرحيم

هناك مشكله معى فى اضافة div لاعرض بها صورة داخل الجريدفيو انا استخدم هذا الكود لتحجيم صورة واضافتها داخل الجريدفيو

هذا الخطأ يظهر

Object reference not set to an instance of an object

ملاحظة الخطأ يظهر لى فى اخر سطر

s.InnerHtml = "<img src=" + imageurl + " border='0' " + s_ImageSize + "/>"

الكود المستخدم

Public Function COMMONFUNCTIONS_IMAGES_RESIZE_TO_TAG(ByVal img As System.Drawing.Image, ByVal MaxWidth As Integer, ByVal MaxHeight As Integer) As String
		If img.Width > MaxWidth Or img.Height > MaxHeight Then
			Dim widthRatio As Double = Convert.ToDouble(img.Width / MaxWidth)
			Dim heightRatio As Double = Convert.ToDouble(img.Height / MaxHeight)
			Dim ratio As Double = Math.Max(widthRatio, heightRatio)
			Dim newWidth As Integer = Convert.ToInt32(img.Width / ratio)
			Dim newHeight As Integer = Convert.ToInt32(img.Height / ratio)
			Return "< width=" + newWidth.ToString() + "  height= " + newHeight.ToString() + " />"
		Else
			Return ""
		End If
	End Function
	Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
		Dim imageurl As String = "img_01.jpg"
		Dim Img_Width As Integer = Convert.ToInt32(100)
		Dim Img_Height As Integer = Convert.ToInt32(100)
		Dim s_ImageSize As String = "<>"
		If File.Exists(Server.MapPath(imageurl)) Then
			s_ImageSize = COMMONFUNCTIONS_IMAGES_RESIZE_TO_TAG(System.Drawing.Image.FromFile(Server.MapPath(imageurl)), Img_Width, Img_Height)
		End If
		Dim s As New System.Web.UI.HtmlControls.HtmlGenericControl("div1")
		s = GridView1.FindControl("div1")
		s.InnerHtml = "<img src=" + imageurl + "  border='0' " + s_ImageSize + "/>"
	End Sub

برجاء المساعده وجزاكم الله خيرا