public void StartLoop_InOneLine() => LoopMethod().Loop(FuncBoolToStopLoop());

public void StartLoop_InOneLine() => LoopMethod.Loop(FuncBoolToStopLoop());

public static class LoopExtensions
        {
            public static void Loop(this Action method, Func<bool> loopUntil)
            {
                while(loopUntil.Invoke())
                method.Invoke();
            }
        }

public class Looping
    {
        //what I would like to do
        public void StartLoop_InOneLine() => LoopMethod().Loop(FuncBoolToStopLoop());

        //what I want to achieve, in practice
        public void StartLoop_InPractice()
        {
            Action method = LoopMethod;
            Func<bool> loopUntil = FuncBoolToStopLoop;

            method.Loop(loopUntil);
        }

        private void LoopMethod(){}

        private bool FuncBoolToStopLoop() => true;
    }