diff --git a/osu.Desktop.Deploy/Program.cs b/osu.Desktop.Deploy/Program.cs
index e13b63f602..3c1d532c0f 100644
--- a/osu.Desktop.Deploy/Program.cs
+++ b/osu.Desktop.Deploy/Program.cs
@@ -310,12 +310,12 @@ namespace osu.Desktop.Deploy
 
                 foreach (var tag in toUpdate)
                 {
-                    int startIndex = l.IndexOf(tag);
+                    int startIndex = l.IndexOf(tag, StringComparison.InvariantCulture);
                     if (startIndex == -1)
                         continue;
                     startIndex += tag.Length;
 
-                    int endIndex = l.IndexOf("<", startIndex);
+                    int endIndex = l.IndexOf("<", startIndex, StringComparison.InvariantCulture);
                     line = $"{l.Substring(0, startIndex)}{version}{l.Substring(endIndex)}";
                 }
 
diff --git a/osu.Desktop/OsuGameDesktop.cs b/osu.Desktop/OsuGameDesktop.cs
index b8eeeb1a5b..ff4b37a8fb 100644
--- a/osu.Desktop/OsuGameDesktop.cs
+++ b/osu.Desktop/OsuGameDesktop.cs
@@ -5,13 +5,16 @@ using System;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
-using Microsoft.Win32;
 using osu.Desktop.Overlays;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Platform;
 using osu.Game;
 using OpenTK.Input;
 
+#if NET461
+using Microsoft.Win32;
+#endif
+
 namespace osu.Desktop
 {
     internal class OsuGameDesktop : OsuGame
@@ -45,9 +48,9 @@ namespace osu.Desktop
             {
                 Func<string, bool> checkExists = p => Directory.Exists(Path.Combine(p, "Songs"));
 
+#if NET461
                 string stableInstallPath;
 
-#if NET461
                 try
                 {
                     using (RegistryKey key = Registry.ClassesRoot.OpenSubKey("osu"))
@@ -61,7 +64,11 @@ namespace osu.Desktop
                 }
 #endif
 
+#if NET461
                 stableInstallPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), @"osu!");
+#else
+                var stableInstallPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), @"osu!");
+#endif
                 if (checkExists(stableInstallPath))
                     return stableInstallPath;
 
diff --git a/osu.Desktop/Overlays/VersionManager.cs b/osu.Desktop/Overlays/VersionManager.cs
index 8bb9d596d1..fef7e6d52a 100644
--- a/osu.Desktop/Overlays/VersionManager.cs
+++ b/osu.Desktop/Overlays/VersionManager.cs
@@ -1,9 +1,7 @@
 // Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
-using System;
 using System.Diagnostics;
-using System.Net.Http;
 using osu.Framework.Allocation;
 using osu.Framework.Development;
 using osu.Framework.Graphics;
@@ -12,7 +10,6 @@ using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.Graphics.Textures;
-using osu.Framework.Logging;
 using osu.Game;
 using osu.Game.Configuration;
 using osu.Game.Graphics;
@@ -23,6 +20,9 @@ using OpenTK;
 using OpenTK.Graphics;
 
 #if NET461
+using System;
+using System.Net.Http;
+using osu.Framework.Logging;
 using Squirrel;
 #endif
 
@@ -101,8 +101,10 @@ namespace osu.Desktop.Overlays
                 }
             };
 
+#if NET461
             if (game.IsDeployedBuild)
                 checkForUpdateAsync();
+#endif
         }
 
         protected override void LoadComplete()
@@ -150,9 +152,9 @@ namespace osu.Desktop.Overlays
 #endif
         }
 
+#if NET461
         private async void checkForUpdateAsync(bool useDeltaPatching = true, UpdateProgressNotification notification = null)
         {
-#if NET461
             //should we schedule a retry on completion of this check?
             bool scheduleRetry = true;
 
@@ -223,8 +225,8 @@ namespace osu.Desktop.Overlays
                         notification.State = ProgressNotificationState.Cancelled;
                 }
             }
-#endif
         }
+#endif
 
         protected override void PopIn()
         {
diff --git a/osu.Game.Rulesets.Osu/UI/Cursor/CursorTrail.cs b/osu.Game.Rulesets.Osu/UI/Cursor/CursorTrail.cs
index a5be6a7952..793a9b73ad 100644
--- a/osu.Game.Rulesets.Osu/UI/Cursor/CursorTrail.cs
+++ b/osu.Game.Rulesets.Osu/UI/Cursor/CursorTrail.cs
@@ -128,6 +128,7 @@ namespace osu.Game.Rulesets.Osu.UI.Cursor
             {
                 Trace.Assert(lastPosition.HasValue);
 
+                // ReSharper disable once PossibleInvalidOperationException
                 Vector2 pos1 = lastPosition.Value;
                 Vector2 diff = pos2 - pos1;
                 float distance = diff.Length;
diff --git a/osu.Game/Beatmaps/BeatmapManager.cs b/osu.Game/Beatmaps/BeatmapManager.cs
index 4bce2a96da..13cefc6a73 100644
--- a/osu.Game/Beatmaps/BeatmapManager.cs
+++ b/osu.Game/Beatmaps/BeatmapManager.cs
@@ -307,6 +307,7 @@ namespace osu.Game.Beatmaps
                     context.ChangeTracker.AutoDetectChangesEnabled = false;
 
                     // re-fetch the beatmap set on the import context.
+                    // ReSharper disable once AccessToModifiedClosure
                     beatmapSet = context.BeatmapSetInfo.Include(s => s.Files).ThenInclude(f => f.FileInfo).First(s => s.ID == beatmapSet.ID);
 
                     // create local stores so we can isolate and thread safely, and share a context/transaction.
diff --git a/osu.Game/Graphics/Cursor/MenuCursor.cs b/osu.Game/Graphics/Cursor/MenuCursor.cs
index da117a94c1..451422038f 100644
--- a/osu.Game/Graphics/Cursor/MenuCursor.cs
+++ b/osu.Game/Graphics/Cursor/MenuCursor.cs
@@ -33,6 +33,7 @@ namespace osu.Game.Graphics.Cursor
 
                 // don't start rotating until we're moved a minimum distance away from the mouse down location,
                 // else it can have an annoying effect.
+                // ReSharper disable once PossibleInvalidOperationException
                 startRotation |= Vector2Extensions.Distance(state.Mouse.Position, state.Mouse.PositionMouseDown.Value) > 30;
 
                 if (startRotation)
diff --git a/osu.Game/IO/Legacy/SerializationReader.cs b/osu.Game/IO/Legacy/SerializationReader.cs
index e79eef4e2b..393a13448e 100644
--- a/osu.Game/IO/Legacy/SerializationReader.cs
+++ b/osu.Game/IO/Legacy/SerializationReader.cs
@@ -186,6 +186,7 @@ namespace osu.Game.IO.Legacy
 
                 Debug.Assert(formatter != null, "formatter != null");
 
+                // ReSharper disable once PossibleNullReferenceException
                 return formatter.Deserialize(stream);
             }
 
diff --git a/osu.Game/Online/API/OAuth.cs b/osu.Game/Online/API/OAuth.cs
index ca38f72904..198c71f0c1 100644
--- a/osu.Game/Online/API/OAuth.cs
+++ b/osu.Game/Online/API/OAuth.cs
@@ -96,6 +96,7 @@ namespace osu.Game.Online.API
 
                 // if not, let's try using our refresh token to request a new access token.
                 if (!string.IsNullOrEmpty(Token?.RefreshToken))
+                    // ReSharper disable once PossibleNullReferenceException
                     AuthenticateWithRefresh(Token.RefreshToken);
 
                 return accessTokenValid;
diff --git a/osu.Game/Online/API/Requests/GetUserBeatmapsRequest.cs b/osu.Game/Online/API/Requests/GetUserBeatmapsRequest.cs
index a66799f404..923ae0e269 100644
--- a/osu.Game/Online/API/Requests/GetUserBeatmapsRequest.cs
+++ b/osu.Game/Online/API/Requests/GetUserBeatmapsRequest.cs
@@ -19,6 +19,7 @@ namespace osu.Game.Online.API.Requests
             this.type = type;
         }
 
+        // ReSharper disable once ImpureMethodCallOnReadonlyValueField
         protected override string Target => $@"users/{userId}/beatmapsets/{type.ToString().Underscore()}?offset={offset}";
     }
 
diff --git a/osu.Game/Online/API/Requests/GetUserScoresRequest.cs b/osu.Game/Online/API/Requests/GetUserScoresRequest.cs
index 98db234196..e30a449978 100644
--- a/osu.Game/Online/API/Requests/GetUserScoresRequest.cs
+++ b/osu.Game/Online/API/Requests/GetUserScoresRequest.cs
@@ -18,6 +18,7 @@ namespace osu.Game.Online.API.Requests
             this.offset = offset;
         }
 
+        // ReSharper disable once ImpureMethodCallOnReadonlyValueField
         protected override string Target => $@"users/{userId}/scores/{type.ToString().ToLower()}?offset={offset}";
     }
 
@@ -27,4 +28,4 @@ namespace osu.Game.Online.API.Requests
         Firsts,
         Recent
     }
-}
\ No newline at end of file
+}
diff --git a/osu.Game/Online/API/Requests/SearchBeatmapSetsRequest.cs b/osu.Game/Online/API/Requests/SearchBeatmapSetsRequest.cs
index 56858b3d56..b949bf35f0 100644
--- a/osu.Game/Online/API/Requests/SearchBeatmapSetsRequest.cs
+++ b/osu.Game/Online/API/Requests/SearchBeatmapSetsRequest.cs
@@ -27,6 +27,7 @@ namespace osu.Game.Online.API.Requests
             this.direction = direction;
         }
 
+        // ReSharper disable once ImpureMethodCallOnReadonlyValueField
         protected override string Target => $@"beatmapsets/search?q={query}&m={ruleset.ID ?? 0}&s={(int)rankStatus}&sort={sortCriteria.ToString().ToLower()}_{directionString}";
     }
 }
diff --git a/osu.Game/Online/Chat/Message.cs b/osu.Game/Online/Chat/Message.cs
index 79b5c4fc1a..972e4755c9 100644
--- a/osu.Game/Online/Chat/Message.cs
+++ b/osu.Game/Online/Chat/Message.cs
@@ -57,6 +57,7 @@ namespace osu.Game.Online.Chat
 
         public virtual bool Equals(Message other) => Id == other?.Id;
 
+        // ReSharper disable once ImpureMethodCallOnReadonlyValueField
         public override int GetHashCode() => Id.GetHashCode();
     }
 
diff --git a/osu.Game/Overlays/ChatOverlay.cs b/osu.Game/Overlays/ChatOverlay.cs
index 24fc322199..ef514c95fd 100644
--- a/osu.Game/Overlays/ChatOverlay.cs
+++ b/osu.Game/Overlays/ChatOverlay.cs
@@ -207,6 +207,7 @@ namespace osu.Game.Overlays
             {
                 Trace.Assert(state.Mouse.PositionMouseDown != null);
 
+                // ReSharper disable once PossibleInvalidOperationException
                 double targetChatHeight = startDragChatHeight - (state.Mouse.Position.Y - state.Mouse.PositionMouseDown.Value.Y) / Parent.DrawSize.Y;
 
                 // If the channel selection screen is shown, mind its minimum height
@@ -380,6 +381,7 @@ namespace osu.Game.Overlays
         {
             if (channel == null) return;
 
+            // ReSharper disable once AccessToModifiedClosure
             var existing = careChannels.Find(c => c.Id == channel.Id);
 
             if (existing != null)
diff --git a/osu.Game/Overlays/MusicController.cs b/osu.Game/Overlays/MusicController.cs
index a99ce89a36..cf8946e399 100644
--- a/osu.Game/Overlays/MusicController.cs
+++ b/osu.Game/Overlays/MusicController.cs
@@ -71,6 +71,7 @@ namespace osu.Game.Overlays
         {
             Trace.Assert(state.Mouse.PositionMouseDown != null, "state.Mouse.PositionMouseDown != null");
 
+            // ReSharper disable once PossibleInvalidOperationException
             Vector2 change = state.Mouse.Position - state.Mouse.PositionMouseDown.Value;
 
             // Diminish the drag distance as we go further to simulate "rubber band" feeling.
diff --git a/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs b/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs
index 4f1a85cf2d..ba0e66e04c 100644
--- a/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs
+++ b/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs
@@ -60,6 +60,7 @@ namespace osu.Game.Rulesets.Timing
             DifficultyPoint = other.DifficultyPoint;
         }
 
+        // ReSharper disable once ImpureMethodCallOnReadonlyValueField
         public int CompareTo(MultiplierControlPoint other) => StartTime.CompareTo(other?.StartTime);
     }
 }
diff --git a/osu.Game/Rulesets/UI/RulesetContainer.cs b/osu.Game/Rulesets/UI/RulesetContainer.cs
index 278814ea7e..b627db8aff 100644
--- a/osu.Game/Rulesets/UI/RulesetContainer.cs
+++ b/osu.Game/Rulesets/UI/RulesetContainer.cs
@@ -157,6 +157,7 @@ namespace osu.Game.Rulesets.UI
 
             WorkingBeatmap = workingBeatmap;
             IsForCurrentRuleset = isForCurrentRuleset;
+            // ReSharper disable once PossibleNullReferenceException
             Mods = workingBeatmap.Mods.Value;
 
             RelativeSizeAxes = Axes.Both;
diff --git a/osu.Game/Rulesets/UI/ScrollingPlayfield.cs b/osu.Game/Rulesets/UI/ScrollingPlayfield.cs
index 395248b2fd..cff3a029e6 100644
--- a/osu.Game/Rulesets/UI/ScrollingPlayfield.cs
+++ b/osu.Game/Rulesets/UI/ScrollingPlayfield.cs
@@ -255,6 +255,7 @@ namespace osu.Game.Rulesets.UI
                     var sX = (SpeedAdjustmentContainer)x;
                     var sY = (SpeedAdjustmentContainer)y;
 
+                    // ReSharper disable once ImpureMethodCallOnReadonlyValueField
                     int result = sY.ControlPoint.StartTime.CompareTo(sX.ControlPoint.StartTime);
                     if (result != 0)
                         return result;
diff --git a/osu.Game/Screens/Select/Leaderboards/LeaderboardScore.cs b/osu.Game/Screens/Select/Leaderboards/LeaderboardScore.cs
index 9044938a75..6ddafe085e 100644
--- a/osu.Game/Screens/Select/Leaderboards/LeaderboardScore.cs
+++ b/osu.Game/Screens/Select/Leaderboards/LeaderboardScore.cs
@@ -123,6 +123,7 @@ namespace osu.Game.Screens.Select.Leaderboards
                             Origin = Anchor.CentreLeft,
                             Font = @"Exo2.0-MediumItalic",
                             TextSize = 22,
+                            // ReSharper disable once ImpureMethodCallOnReadonlyValueField
                             Text = RankPosition.ToString(),
                         },
                     },
diff --git a/osu.Game/Screens/Tournament/Drawings.cs b/osu.Game/Screens/Tournament/Drawings.cs
index e540782fc1..269b206a78 100644
--- a/osu.Game/Screens/Tournament/Drawings.cs
+++ b/osu.Game/Screens/Tournament/Drawings.cs
@@ -326,6 +326,7 @@ namespace osu.Game.Screens.Tournament
                             if (line.ToUpper().StartsWith("GROUP"))
                                 continue;
 
+                            // ReSharper disable once AccessToModifiedClosure
                             DrawingsTeam teamToAdd = allTeams.FirstOrDefault(t => t.FullName == line);
 
                             if (teamToAdd == null)
diff --git a/osu.Game/Screens/Tournament/ScrollingTeamContainer.cs b/osu.Game/Screens/Tournament/ScrollingTeamContainer.cs
index 2eb0dacec3..5bae30458e 100644
--- a/osu.Game/Screens/Tournament/ScrollingTeamContainer.cs
+++ b/osu.Game/Screens/Tournament/ScrollingTeamContainer.cs
@@ -13,9 +13,9 @@ using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.Graphics.Textures;
 using osu.Framework.Threading;
+using osu.Game.Screens.Tournament.Teams;
 using OpenTK;
 using OpenTK.Graphics;
-using osu.Game.Screens.Tournament.Teams;
 
 namespace osu.Game.Screens.Tournament
 {
@@ -118,16 +118,18 @@ namespace osu.Game.Screens.Tournament
                         if (!Children.Any())
                             break;
 
-                        Drawable closest = null;
+                        ScrollingTeam closest = null;
 
                         foreach (var c in Children)
                         {
-                            if (!(c is ScrollingTeam))
+                            var stc = c as ScrollingTeam;
+
+                            if (stc == null)
                                 continue;
 
                             if (closest == null)
                             {
-                                closest = c;
+                                closest = stc;
                                 continue;
                             }
 
@@ -135,14 +137,15 @@ namespace osu.Game.Screens.Tournament
                             float lastOffset = Math.Abs(closest.Position.X + closest.DrawWidth / 2f - DrawWidth / 2f);
 
                             if (o < lastOffset)
-                                closest = c;
+                                closest = stc;
                         }
 
                         Trace.Assert(closest != null, "closest != null");
 
+                        // ReSharper disable once PossibleNullReferenceException
                         offset += DrawWidth / 2f - (closest.Position.X + closest.DrawWidth / 2f);
 
-                        ScrollingTeam st = closest as ScrollingTeam;
+                        ScrollingTeam st = closest;
 
                         availableTeams.RemoveAll(at => at == st.Team);
 
diff --git a/osu.Game/Screens/Tournament/Teams/StorageBackedTeamList.cs b/osu.Game/Screens/Tournament/Teams/StorageBackedTeamList.cs
index 1b2d84a666..ce3b5ed941 100644
--- a/osu.Game/Screens/Tournament/Teams/StorageBackedTeamList.cs
+++ b/osu.Game/Screens/Tournament/Teams/StorageBackedTeamList.cs
@@ -38,6 +38,7 @@ namespace osu.Game.Screens.Tournament.Teams
                             if (string.IsNullOrEmpty(line))
                                 continue;
 
+                            // ReSharper disable once PossibleNullReferenceException
                             string[] split = line.Split(':');
 
                             if (split.Length < 2)