Enable TimeSpan with WaitableTimer.

src/AsyncFiberWorks.Windows/Timer/WaitableTimerEx.cs

@@ -49,7 +49,7 @@ public WaitableTimerEx(bool manualReset = true, string timerName = null)
         /// Activate the timer.
         /// see https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-setwaitabletimerex
         /// </summary>
-        /// <param name="dueTime">Initial wait time for timer. 100 nanosecond units.</param>
+        /// <param name="dueTime">Initial wait time for timer. 100 nanosecond units. Be sure to specify a negative value.</param>
         /// <param name="period">The interval at which the timer expires. In milliseconds. If this value is 0, the timer will expire only once; if it is greater than 0, it will expire periodically and continue until canceled.</param>
         /// <exception cref="Win32Exception"></exception>
         public void Set(long dueTime, int period = 0)
@@ -60,6 +60,18 @@ public void Set(long dueTime, int period = 0)
             }
         }
 
+        /// <summary>
+        /// Activate the timer.
+        /// </summary>
+        /// <param name="dueTime">Initial wait time for timer.</param>
+        /// <param name="period">The interval at which the timer expires. In milliseconds. If this value is 0, the timer will expire only once; if it is greater than 0, it will expire periodically and continue until canceled.</param>
+        /// <exception cref="Win32Exception"></exception>
+        public void Set(TimeSpan dueTime, int period = 0)
+        {
+            long convertedDueTime = dueTime.Ticks * -10000L / TimeSpan.TicksPerMillisecond;
+            this.Set(convertedDueTime, period);
+        }
+
         /// <summary>
         /// Deactivate the timer.
         /// see https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-cancelwaitabletimer

src/AsyncFiberWorksTests/TimerActionTests.cs

@@ -84,5 +84,25 @@ public async Task OneshotTimerDelayTest(IOneshotTimerFactory timerFactory)
             new object[] { new WaitableTimerExFactory() },
 #endif
         };
+
+#if NETFRAMEWORK || WINDOWS
+        [Test]
+        public async Task CancelWaitableTimer()
+        {
+            var tcs = new TaskCompletionSource<int>();
+            var timer = new WaitableTimerEx();
+            timer.Set(TimeSpan.FromMilliseconds(300));
+            var tmpHandle = ThreadPool.RegisterWaitForSingleObject(timer, (state, timeout) =>
+            {
+                tcs.SetResult(0);
+            }, null, Timeout.Infinite, executeOnlyOnce: true);
+            await Task.Delay(100).ConfigureAwait(false);
+            bool isCancelled = timer.Cancel();
+            Assert.IsTrue(isCancelled);
+            await Task.Delay(500).ConfigureAwait(false);
+            Assert.IsFalse(tcs.Task.IsCompleted);
+            tmpHandle.Unregister(null);
+        }
+#endif
     }
 }