Normally when i tried to code, and i want to put a if-else block in my code, i do it normally like this.
if (chkD4.Items.Selected == true)
txtD5.Visible = true;
txtD5.Visible = false;
Resharper let me code the same thing in one line.
txtD5.Visible = chkD4.Items.Selected == true;
Its a common thing, usually we code like above, but we should code like below to code like gentleman programmers.