code cleanup

Form1.cs

@@ -42,7 +42,7 @@ namespace CopyAndEncodeImage {
         }
 
         private void textBox1_TextChanged(object sender, EventArgs e) {
-            btnEncode.Enabled = !string.IsNullOrEmpty(textBox1.Text) && System.IO.Path.GetExtension(textBox1.Text).ToLower() == ".png";
+            btnEncode.Enabled = !string.IsNullOrEmpty(textBox1.Text) && Path.GetExtension(textBox1.Text).ToLower() == ".png";
         }
     }
 }