fix bug starting several instances at once

Author: gfody

Tray/OneInstance.cs

@@ -20,27 +20,27 @@ public static bool First(string globalName = null)
 
 		try
 		{
-			mmf = MemoryMappedFile.OpenExisting(globalName);
-			using (var r = mmf.CreateViewAccessor())
-			{
-				r.Read(0, out long value);
-				messageHandle = new IntPtr(value);
-
-				return false;
-			}
-		}
-		catch (FileNotFoundException)
-		{
+			mmf = MemoryMappedFile.CreateNew(globalName, 8);
 			messageWindow = new HwndSource(new HwndSourceParameters());
 			ChangeWindowMessageFilterEx(messageWindow.Handle, WM_COPYDATA, 1, IntPtr.Zero);
-			mmf = MemoryMappedFile.CreateNew(globalName, 8);
 			using (var w = mmf.CreateViewAccessor())
 				w.Write(0, (long)messageWindow.Handle);
 
 			messageWindow.AddHook(WndProc);
 
 			return true;
 		}
+		catch (IOException e) when ((uint)e.HResult == 0x800700B7) // already exists
+		{
+			mmf = MemoryMappedFile.OpenExisting(globalName);
+			using (var r = mmf.CreateViewAccessor())
+			{
+				r.Read(0, out long value);
+				messageHandle = new IntPtr(value);
+
+				return false;
+			}
+		}
 	}
 
 	public static void SendMessage(string message)