Added unit tests and fixed the setting manager.

src/Volo.Abp.Session/Volo/Abp/Settings/UserSettingManagerExtensions.cs

@@ -28,14 +28,14 @@ namespace Volo.Abp.Settings
             return settingManager.GetAllAsync(UserSettingValueProvider.DefaultEntityType, null, fallback);
         }
 
-        public static Task SetForUserAsync(this ISettingManager settingManager, Guid userId, [NotNull] string name, [CanBeNull] string value)
+        public static Task SetForUserAsync(this ISettingManager settingManager, Guid userId, [NotNull] string name, [CanBeNull] string value, bool forceToSet = false)
         {
-            return settingManager.SetAsync(name, value, UserSettingValueProvider.DefaultEntityType, userId.ToString());
+            return settingManager.SetAsync(name, value, UserSettingValueProvider.DefaultEntityType, userId.ToString(), forceToSet);
         }
 
-        public static Task SetForCurrentUserAsync(this ISettingManager settingManager, [NotNull] string name, [CanBeNull] string value)
+        public static Task SetForCurrentUserAsync(this ISettingManager settingManager, [NotNull] string name, [CanBeNull] string value, bool forceToSet = false)
         {
-            return settingManager.SetAsync(name, value, UserSettingValueProvider.DefaultEntityType, null);
+            return settingManager.SetAsync(name, value, UserSettingValueProvider.DefaultEntityType, null, forceToSet);
         }
     }
 }

src/Volo.Abp.Settings/Volo/Abp/Settings/SettingManager.cs

@@ -138,15 +138,6 @@ namespace Volo.Abp.Settings
 
             var setting = SettingDefinitionManager.Get(name);
 
-            if (!forceToSet)
-            {
-                var currentValue = await GetOrNullInternalAsync(name, entityType, entityId);
-                if (currentValue == value)
-                {
-                    return;
-                }
-            }
-
             var providers = Enumerable
                 .Reverse(Providers.Value)
                 .SkipWhile(p => p.EntityType != entityType)
@@ -157,6 +148,20 @@ namespace Volo.Abp.Settings
                 return;
             }
 
+            //Clear the value if it's same as it's fallback value
+            if (providers.Count > 1 && !forceToSet && value != null)
+            {
+                var fallbackValue = await GetOrNullInternalAsync(name, providers[1].EntityType, entityId);
+                if (fallbackValue == value)
+                {
+                    value = null;
+                }
+            }
+
+            providers = providers
+                .TakeWhile(p => p.EntityType == entityType)
+                .ToList();
+
             if (value == null)
             {
                 foreach (var provider in providers)

test/Volo.Abp.Settings.Tests/Volo/Abp/Settings/AbpIdentityApplicationTestBase.cs

@@ -1,4 +1,7 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
+using Volo.Abp.Session;
 using Volo.Abp.Settings.EntityFrameworkCore;
 using Volo.Abp.TestBase;
 
@@ -27,5 +30,16 @@ namespace Volo.Abp.Settings
             }
         }
 
+        protected List<Setting> GetSettingsFromDbContext(string entityType, string entityId, string name)
+        {
+            return UsingDbContext(context =>
+                context.Settings.Where(
+                    s =>
+                        s.EntityType == UserSettingValueProvider.DefaultEntityType &&
+                        s.EntityId == AbpIdentityTestDataBuilder.User1Id.ToString() &&
+                        s.Name == "MySetting2"
+                ).ToList()
+            );
+        }
     }
 }

test/Volo.Abp.Settings.Tests/Volo/Abp/Settings/SettingManager_User_Tests.cs

@@ -109,15 +109,11 @@ namespace Volo.Abp.Settings
         {
             await _settingManager.SetForUserAsync(AbpIdentityTestDataBuilder.User1Id, "MySetting2", null);
 
-            UsingDbContext(context =>
-            {
-                context.Settings.Count(
-                    s =>
-                        s.EntityType == UserSettingValueProvider.DefaultEntityType &&
-                        s.EntityId == AbpIdentityTestDataBuilder.User1Id.ToString() &&
-                        s.Name == "MySetting2"
-                ).ShouldBe(0);
-            });
+            GetSettingsFromDbContext(
+                UserSettingValueProvider.DefaultEntityType,
+                AbpIdentityTestDataBuilder.User1Id.ToString(),
+                "MySetting2"
+            ).Count.ShouldBe(0);
         }
 
         [Fact]
@@ -131,17 +127,50 @@ namespace Volo.Abp.Settings
             (await _settingManager.GetOrNullForUserAsync("MySetting2", AbpIdentityTestDataBuilder.User1Id))
                 .ShouldBe("user1-new-store-value");
 
-            UsingDbContext(context =>
-            {
-                var setting = context.Settings.Single(
-                    s =>
-                        s.EntityType == UserSettingValueProvider.DefaultEntityType &&
-                        s.EntityId == AbpIdentityTestDataBuilder.User1Id.ToString() &&
-                        s.Name == "MySetting2"
-                );
-
-                setting.Value.ShouldBe("user1-new-store-value");
-            });
+            GetSettingsFromDbContext(
+                UserSettingValueProvider.DefaultEntityType,
+                AbpIdentityTestDataBuilder.User1Id.ToString(),
+                "MySetting2"
+            ).Single().Value.ShouldBe("user1-new-store-value");
+        }
+
+        [Fact]
+        public async Task Should_Delete_Setting_Record_When_Set_To_Fallback_Value()
+        {
+            await _settingManager.SetForUserAsync(
+                AbpIdentityTestDataBuilder.User1Id,
+                "MySetting2",
+                "default-store-value"
+            );
+
+            GetSettingsFromDbContext(
+                UserSettingValueProvider.DefaultEntityType,
+                AbpIdentityTestDataBuilder.User1Id.ToString(),
+                "MySetting2"
+            ).Count.ShouldBe(0);
+
+            (await _settingManager.GetOrNullForUserAsync("MySetting2", AbpIdentityTestDataBuilder.User1Id))
+                .ShouldBe("default-store-value");
+        }
+
+        [Fact]
+        public async Task Should_Not_Delete_Setting_Record_When_Set_To_Fallback_Value_If_Forced()
+        {
+            await _settingManager.SetForUserAsync(
+                AbpIdentityTestDataBuilder.User1Id,
+                "MySetting2",
+                "default-store-value",
+                forceToSet: true
+            );
+
+            GetSettingsFromDbContext(
+                UserSettingValueProvider.DefaultEntityType,
+                AbpIdentityTestDataBuilder.User1Id.ToString(),
+                "MySetting2"
+            ).Single().Value.ShouldBe("default-store-value");
+
+            (await _settingManager.GetOrNullForUserAsync("MySetting2", AbpIdentityTestDataBuilder.User1Id))
+                .ShouldBe("default-store-value");
         }
     }
 }