Release event?

Why does this give an error…trying to use the release event

   btn.ReleaseEvent += new OnRelease(btn_Releaseit);
        }

        static void btn_Releaseit(object sender)
        {//do something
        }

Error 1 Cannot implicitly convert type ‘GHIElectronics.NETMF.Glide.OnRelease’ to ‘GHIElectronics.NETMF.Glide.OnPress’
C:\Users\n\Projects\Glide_Button\Glide_Button\Program.cs 42 33 Glide_Button

try

btn.ReleaseEvent += btn_Releaseit;