how can define silder variable in unity 5.3

try define Slider variable in C# but seems unity cant recognize Slider .

i want add this code in my c# in unity 5.3 : public Slider myslider; . what can i do ?

Have you added
using UnityEngine.UI;
at the top of your script? That is needed for the script to understand what you mean when referring directly to “Slider”!