iOS Question how to convert object to imageview

Sub SetBackgroundImage(b As Object, bmp As Bitmap, state As Int)

   If b Is Button Then
       Dim no As NativeObject = b
       no.RunMethod("setBackgroundImage:forState:", Array(bmp, state))
   End If
   
   If b Is ImageView Then
       b.Bitmap = LoadBitmap(File.DirAssets, "test.png")  //this line is error
       
   End If
   
   

End Sub