diff --git a/common/ASC.Common/Data/DataExtensions.cs b/common/ASC.Common/Data/DataExtensions.cs
index 28d098ed4a..ada8bbd088 100644
--- a/common/ASC.Common/Data/DataExtensions.cs
+++ b/common/ASC.Common/Data/DataExtensions.cs
@@ -92,8 +92,7 @@ namespace ASC.Common.Data
                 return DBNull.Value;
             }
 
-            var @enum = value as Enum;
-            if (@enum != null)
+            if (value is Enum @enum)
             {
                 return @enum.ToString("d");
             }
diff --git a/common/ASC.Common/Data/DbManager.cs b/common/ASC.Common/Data/DbManager.cs
index 73ce3396ed..e8c8fbac58 100644
--- a/common/ASC.Common/Data/DbManager.cs
+++ b/common/ASC.Common/Data/DbManager.cs
@@ -128,8 +128,7 @@ namespace ASC.Common.Data
         {
             if (HttpContext.Current != null)
             {
-                var dbManager = DisposableHttpContext.Current[databaseId] as DbManager;
-                if (dbManager == null || dbManager.disposed)
+                if (!(DisposableHttpContext.Current[databaseId] is DbManager dbManager) || dbManager.disposed)
                 {
                     var localDbManager = new DbManager(databaseId);
                     var dbManagerAdapter = new DbManagerProxy(localDbManager);
diff --git a/common/ASC.Common/DependencyInjection/DictionaryElementCollection.cs b/common/ASC.Common/DependencyInjection/DictionaryElementCollection.cs
index 79f25e7ee8..4a5147729c 100644
--- a/common/ASC.Common/DependencyInjection/DictionaryElementCollection.cs
+++ b/common/ASC.Common/DependencyInjection/DictionaryElementCollection.cs
@@ -46,8 +46,7 @@ namespace ASC.Common.DependencyInjection
             public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, System.Type destinationType)
             {
                 var instantiableType = GetInstantiableType(destinationType);
-                var elementCollection = value as DictionaryElementCollection;
-                if (elementCollection == null || !(instantiableType != null))
+                if (!(value is DictionaryElementCollection elementCollection) || !(instantiableType != null))
                     return base.ConvertTo(context, culture, value, destinationType);
                 var dictionary = (IDictionary)Activator.CreateInstance(instantiableType);
                 var genericArguments = instantiableType.GetGenericArguments();
diff --git a/common/ASC.Common/DependencyInjection/TypeManipulation.cs b/common/ASC.Common/DependencyInjection/TypeManipulation.cs
index c2dabc7248..2e0e60bbf1 100644
--- a/common/ASC.Common/DependencyInjection/TypeManipulation.cs
+++ b/common/ASC.Common/DependencyInjection/TypeManipulation.cs
@@ -77,8 +77,7 @@ namespace ASC.Common.DependencyInjection
 
         private static TypeConverter GetTypeConverterFromName(string converterTypeName)
         {
-            var typeConverter = Activator.CreateInstance(Type.GetType(converterTypeName, true)) as TypeConverter;
-            if (typeConverter == null)
+            if (!(Activator.CreateInstance(Type.GetType(converterTypeName, true)) is TypeConverter typeConverter))
                 throw new ConfigurationErrorsException("");
             return typeConverter;
         }
diff --git a/common/ASC.Common/Security/Authentication/Account.cs b/common/ASC.Common/Security/Authentication/Account.cs
index 96cfab0af5..a81ecadba5 100644
--- a/common/ASC.Common/Security/Authentication/Account.cs
+++ b/common/ASC.Common/Security/Authentication/Account.cs
@@ -65,8 +65,7 @@ namespace ASC.Common.Security.Authentication
 
         public override bool Equals(object obj)
         {
-            var a = obj as IAccount;
-            return a != null && ID.Equals(a.ID);
+            return obj is IAccount a && ID.Equals(a.ID);
         }
 
         public override int GetHashCode()
diff --git a/common/ASC.Common/Security/Authorizing/Domain/Action.cs b/common/ASC.Common/Security/Authorizing/Domain/Action.cs
index d4e294a83f..6ad1db4f41 100644
--- a/common/ASC.Common/Security/Authorizing/Domain/Action.cs
+++ b/common/ASC.Common/Security/Authorizing/Domain/Action.cs
@@ -62,8 +62,7 @@ namespace ASC.Common.Security.Authorizing
 
         public override bool Equals(object obj)
         {
-            var a = obj as Action;
-            return a != null && a.ID == ID;
+            return obj is Action a && a.ID == ID;
         }
 
         public override string ToString()
diff --git a/common/ASC.Common/Security/Authorizing/Domain/Role.cs b/common/ASC.Common/Security/Authorizing/Domain/Role.cs
index 123fa4940f..5cc7590125 100644
--- a/common/ASC.Common/Security/Authorizing/Domain/Role.cs
+++ b/common/ASC.Common/Security/Authorizing/Domain/Role.cs
@@ -70,8 +70,7 @@ namespace ASC.Common.Security.Authorizing
 
         public override bool Equals(object obj)
         {
-            var r = obj as Role;
-            return r != null && r.ID == ID;
+            return obj is Role r && r.ID == ID;
         }
 
         public override string ToString()
diff --git a/common/ASC.Common/Security/SecurityObjectId.cs b/common/ASC.Common/Security/SecurityObjectId.cs
index 92287a91d0..d81152cdc7 100644
--- a/common/ASC.Common/Security/SecurityObjectId.cs
+++ b/common/ASC.Common/Security/SecurityObjectId.cs
@@ -51,8 +51,7 @@ namespace ASC.Common.Security
 
         public override bool Equals(object obj)
         {
-            var other = obj as SecurityObjectId;
-            return other != null &&
+            return obj is SecurityObjectId other &&
                    Equals(AzObjectIdHelper.GetFullObjectId(other), AzObjectIdHelper.GetFullObjectId(this));
         }
     }
diff --git a/common/ASC.Common/Threading/Workers/WorkItem.cs b/common/ASC.Common/Threading/Workers/WorkItem.cs
index 89c29e1898..65f3c7fe76 100644
--- a/common/ASC.Common/Threading/Workers/WorkItem.cs
+++ b/common/ASC.Common/Threading/Workers/WorkItem.cs
@@ -64,8 +64,7 @@ namespace ASC.Common.Threading.Workers
             {
                 if (disposing)
                 {
-                    var disposable = Item as IDisposable;
-                    if (disposable != null)
+                    if (Item is IDisposable disposable)
                     {
                         disposable.Dispose();
                     }
diff --git a/common/ASC.Core.Common/Billing/Tariff.cs b/common/ASC.Core.Common/Billing/Tariff.cs
index 6ccf53a6da..4e998b7936 100644
--- a/common/ASC.Core.Common/Billing/Tariff.cs
+++ b/common/ASC.Core.Common/Billing/Tariff.cs
@@ -69,8 +69,7 @@ namespace ASC.Core.Billing
 
         public override bool Equals(object obj)
         {
-            var t = obj as Tariff;
-            return t != null && t.QuotaId == QuotaId;
+            return obj is Tariff t && t.QuotaId == QuotaId;
         }
     }
 }
\ No newline at end of file
diff --git a/common/ASC.Core.Common/Billing/TariffService.cs b/common/ASC.Core.Common/Billing/TariffService.cs
index a5df0bdd52..ed597ad217 100644
--- a/common/ASC.Core.Common/Billing/TariffService.cs
+++ b/common/ASC.Core.Common/Billing/TariffService.cs
@@ -256,8 +256,7 @@ namespace ASC.Core.Billing
                           ? GetBillingUrlCacheKey(tenant.Value)
                           : string.Format("notenant{0}", !string.IsNullOrEmpty(affiliateId) ? "_" + affiliateId : "");
             key += quota.Visible ? "" : "0";
-            var urls = cache.Get<Dictionary<string, Tuple<Uri, Uri>>>(key) as IDictionary<string, Tuple<Uri, Uri>>;
-            if (urls == null)
+            if (!(cache.Get<Dictionary<string, Tuple<Uri, Uri>>>(key) is IDictionary<string, Tuple<Uri, Uri>> urls))
             {
                 urls = new Dictionary<string, Tuple<Uri, Uri>>();
                 if (billingConfigured)
diff --git a/common/ASC.Core.Common/Caching/CachedUserService.cs b/common/ASC.Core.Common/Caching/CachedUserService.cs
index 3554bfa02b..28ce9f8bc0 100644
--- a/common/ASC.Core.Common/Caching/CachedUserService.cs
+++ b/common/ASC.Core.Common/Caching/CachedUserService.cs
@@ -221,8 +221,7 @@ namespace ASC.Core.Caching
             GetChangesFromDb();
 
             var key = GetRefCacheKey(tenant);
-            var refs = cache.Get<UserGroupRefStore>(key) as IDictionary<string, UserGroupRef>;
-            if (refs == null)
+            if (!(cache.Get<UserGroupRefStore>(key) is IDictionary<string, UserGroupRef> refs))
             {
                 refs = service.GetUserGroupRefs(tenant, default);
                 cache.Insert(key, new UserGroupRefStore(refs), CacheExpiration);
diff --git a/common/ASC.Core.Common/Context/Impl/AuthorizationManager.cs b/common/ASC.Core.Common/Context/Impl/AuthorizationManager.cs
index 88917242c0..720efcf3c6 100644
--- a/common/ASC.Core.Common/Context/Impl/AuthorizationManager.cs
+++ b/common/ASC.Core.Common/Context/Impl/AuthorizationManager.cs
@@ -118,8 +118,7 @@ namespace ASC.Core
         private IEnumerable<AzRecord> FilterAces(IEnumerable<AzRecord> aces, Guid subjectId, Guid actionId, ISecurityObjectId objectId)
         {
             var objId = AzObjectIdHelper.GetFullObjectId(objectId);
-            var store = aces as AzRecordStore;
-            return store != null ?
+            return aces is AzRecordStore store ?
                 store.Get(objId).Where(a => (a.SubjectId == subjectId || subjectId == Guid.Empty) && (a.ActionId == actionId || actionId == Guid.Empty)) :
                 aces.Where(a => (a.SubjectId == subjectId || subjectId == Guid.Empty) && (a.ActionId == actionId || actionId == Guid.Empty) && a.ObjectId == objId);
         }
diff --git a/common/ASC.Core.Common/Context/Impl/TenantManager.cs b/common/ASC.Core.Common/Context/Impl/TenantManager.cs
index 4d1d27d514..409c249f66 100644
--- a/common/ASC.Core.Common/Context/Impl/TenantManager.cs
+++ b/common/ASC.Core.Common/Context/Impl/TenantManager.cs
@@ -127,8 +127,7 @@ namespace ASC.Core
         {
             var newTenant = tenantService.SaveTenant(tenant);
 
-            var oldTenant = CallContext.GetData(CURRENT_TENANT) as Tenant;
-            if (oldTenant != null) SetCurrentTenant(newTenant);
+            if (CallContext.GetData(CURRENT_TENANT) is Tenant oldTenant) SetCurrentTenant(newTenant);
 
             return newTenant;
         }
diff --git a/common/ASC.Core.Common/Context/Impl/UserManager.cs b/common/ASC.Core.Common/Context/Impl/UserManager.cs
index bfbb6b94c5..55a67c392e 100644
--- a/common/ASC.Core.Common/Context/Impl/UserManager.cs
+++ b/common/ASC.Core.Common/Context/Impl/UserManager.cs
@@ -280,8 +280,7 @@ namespace ASC.Core
 
             var refs = GetRefsInternal(tenant.TenantId);
             IEnumerable<UserGroupRef> userRefs = null;
-            var store = refs as UserGroupRefStore;
-            if (store != null)
+            if (refs is UserGroupRefStore store)
             {
                 userRefs = store.GetRefsByUser(userID);
             }
@@ -313,8 +312,7 @@ namespace ASC.Core
 
             var refs = GetRefsInternal(tenantId);
 
-            var store = refs as UserGroupRefStore;
-            if (store != null)
+            if (refs is UserGroupRefStore store)
             {
                 var userRefs = store.GetRefsByUser(userID);
 
diff --git a/common/ASC.Core.Common/Context/WorkContext.cs b/common/ASC.Core.Common/Context/WorkContext.cs
index 07291c2ef1..df455b7e4c 100644
--- a/common/ASC.Core.Common/Context/WorkContext.cs
+++ b/common/ASC.Core.Common/Context/WorkContext.cs
@@ -144,8 +144,7 @@ namespace ASC.Core
 
         private static void NotifyEngine_AfterTransferRequest(NotifyEngine sender, NotifyRequest request)
         {
-            var tenant = (request.Properties.Contains("Tenant") ? request.Properties["Tenant"] : null) as Tenant;
-            if (tenant != null)
+            if ((request.Properties.Contains("Tenant") ? request.Properties["Tenant"] : null) is Tenant tenant)
             {
                 CoreContext.TenantManager.SetCurrentTenant(tenant);
             }
diff --git a/common/ASC.Core.Common/Core/AzRecord.cs b/common/ASC.Core.Common/Core/AzRecord.cs
index 84fa2f933b..c50b53657d 100644
--- a/common/ASC.Core.Common/Core/AzRecord.cs
+++ b/common/ASC.Core.Common/Core/AzRecord.cs
@@ -106,8 +106,7 @@ namespace ASC.Core
 
         public override bool Equals(object obj)
         {
-            var r = obj as AzRecord;
-            return r != null &&
+            return obj is AzRecord r &&
                 r.Tenant == Tenant &&
                 r.SubjectId == SubjectId &&
                 r.ActionId == ActionId &&
diff --git a/common/ASC.Core.Common/Core/DBResourceManager.cs b/common/ASC.Core.Common/Core/DBResourceManager.cs
index d9bfccdc39..3b0176dfc3 100644
--- a/common/ASC.Core.Common/Core/DBResourceManager.cs
+++ b/common/ASC.Core.Common/Core/DBResourceManager.cs
@@ -234,8 +234,7 @@ namespace TMResourceData
             private Dictionary<string, string> GetResources()
             {
                 var key = string.Format("{0}/{1}", filename, culture);
-                var dic = cache.Get(key) as Dictionary<string, string>;
-                if (dic == null)
+                if (!(cache.Get(key) is Dictionary<string, string> dic))
                 {
                     lock (locker)
                     {
diff --git a/common/ASC.Core.Common/Core/Group.cs b/common/ASC.Core.Common/Core/Group.cs
index d028ac8a0b..e8feec8ab0 100644
--- a/common/ASC.Core.Common/Core/Group.cs
+++ b/common/ASC.Core.Common/Core/Group.cs
@@ -90,8 +90,7 @@ namespace ASC.Core
 
         public override bool Equals(object obj)
         {
-            var g = obj as Group;
-            return g != null && g.Id == Id;
+            return obj is Group g && g.Id == Id;
         }
     }
 }
diff --git a/common/ASC.Core.Common/Core/GroupInfo.cs b/common/ASC.Core.Common/Core/GroupInfo.cs
index 93e640057a..514d020af8 100644
--- a/common/ASC.Core.Common/Core/GroupInfo.cs
+++ b/common/ASC.Core.Common/Core/GroupInfo.cs
@@ -65,8 +65,7 @@ namespace ASC.Core.Users
 
         public override bool Equals(object obj)
         {
-            var g = obj as GroupInfo;
-            if (g == null) return false;
+            if (!(obj is GroupInfo g)) return false;
             if (ID == Guid.Empty && g.ID == Guid.Empty) return ReferenceEquals(this, g);
             return g.ID == ID;
         }
diff --git a/common/ASC.Core.Common/Core/Partner.cs b/common/ASC.Core.Common/Core/Partner.cs
index 7b681d88af..b8eb0b3632 100644
--- a/common/ASC.Core.Common/Core/Partner.cs
+++ b/common/ASC.Core.Common/Core/Partner.cs
@@ -169,8 +169,7 @@ namespace ASC.Core
 
         public override bool Equals(object obj)
         {
-            var p = obj as Partner;
-            return p != null && p.Id == Id;
+            return obj is Partner p && p.Id == Id;
         }
 
         public override int GetHashCode()
diff --git a/common/ASC.Core.Common/Core/UserGroupRef.cs b/common/ASC.Core.Common/Core/UserGroupRef.cs
index bbec0474bb..6598adbb87 100644
--- a/common/ASC.Core.Common/Core/UserGroupRef.cs
+++ b/common/ASC.Core.Common/Core/UserGroupRef.cs
@@ -74,8 +74,7 @@ namespace ASC.Core
 
         public override bool Equals(object obj)
         {
-            var r = obj as UserGroupRef;
-            return r != null && r.Tenant == Tenant && r.UserId == UserId && r.GroupId == GroupId && r.RefType == RefType;
+            return obj is UserGroupRef r && r.Tenant == Tenant && r.UserId == UserId && r.GroupId == GroupId && r.RefType == RefType;
         }
 
         public static implicit operator UserGroupRef(UserGroupRefCacheItem cache)
diff --git a/common/ASC.Core.Common/Core/UserInfo.cs b/common/ASC.Core.Common/Core/UserInfo.cs
index c6823871b3..de518ab8e6 100644
--- a/common/ASC.Core.Common/Core/UserInfo.cs
+++ b/common/ASC.Core.Common/Core/UserInfo.cs
@@ -116,8 +116,7 @@ namespace ASC.Core.Users
 
         public override bool Equals(object obj)
         {
-            var ui = obj as UserInfo;
-            return ui != null && ID.Equals(ui.ID);
+            return obj is UserInfo ui && ID.Equals(ui.ID);
         }
 
         public CultureInfo GetCulture()
diff --git a/common/ASC.Core.Common/Notify/Engine/InterceptorStorage.cs b/common/ASC.Core.Common/Notify/Engine/InterceptorStorage.cs
index e4971a6642..51e704a223 100644
--- a/common/ASC.Core.Common/Notify/Engine/InterceptorStorage.cs
+++ b/common/ASC.Core.Common/Notify/Engine/InterceptorStorage.cs
@@ -41,8 +41,7 @@ namespace ASC.Notify.Engine
         {
             get
             {
-                var storage = CallContext.GetData(CallContext_Prefix) as Dictionary<string, ISendInterceptor>;
-                if (storage == null)
+                if (!(CallContext.GetData(CallContext_Prefix) is Dictionary<string, ISendInterceptor> storage))
                 {
                     storage = new Dictionary<string, ISendInterceptor>(10);
                     CallContext.SetData(CallContext_Prefix, storage);
diff --git a/common/ASC.Core.Common/Notify/Engine/NotifyEngine.cs b/common/ASC.Core.Common/Notify/Engine/NotifyEngine.cs
index 707f1cf014..9841ee8892 100644
--- a/common/ASC.Core.Common/Notify/Engine/NotifyEngine.cs
+++ b/common/ASC.Core.Common/Notify/Engine/NotifyEngine.cs
@@ -401,8 +401,7 @@ namespace ASC.Notify.Engine
 
         private SendResponse SendDirectNotify(int tenantId, NotifyRequest request, ISenderChannel channel)
         {
-            var recipient = request.Recipient as IDirectRecipient;
-            if (recipient == null) throw new ArgumentException("request.Recipient not IDirectRecipient", "request");
+            if (!(request.Recipient is IDirectRecipient recipient)) throw new ArgumentException("request.Recipient not IDirectRecipient", "request");
 
             request.CurrentSender = channel.SenderName;
 
@@ -488,8 +487,7 @@ namespace ASC.Notify.Engine
             {
                 if (!stylers.ContainsKey(message.Pattern.Styler))
                 {
-                    var styler = Activator.CreateInstance(Type.GetType(message.Pattern.Styler, true)) as IPatternStyler;
-                    if (styler != null)
+                    if (Activator.CreateInstance(Type.GetType(message.Pattern.Styler, true)) is IPatternStyler styler)
                     {
                         stylers.Add(message.Pattern.Styler, styler);
                     }
diff --git a/common/ASC.Core.Common/Notify/Model/NotifyAction.cs b/common/ASC.Core.Common/Notify/Model/NotifyAction.cs
index 6f3e4cb306..31b247560f 100644
--- a/common/ASC.Core.Common/Notify/Model/NotifyAction.cs
+++ b/common/ASC.Core.Common/Notify/Model/NotifyAction.cs
@@ -59,8 +59,7 @@ namespace ASC.Notify.Model
 
         public override bool Equals(object obj)
         {
-            var a = obj as INotifyAction;
-            return a != null && a.ID == ID;
+            return obj is INotifyAction a && a.ID == ID;
         }
 
         public override int GetHashCode()
diff --git a/common/ASC.Core.Common/Notify/Patterns/NVelocityPatternFormatter.cs b/common/ASC.Core.Common/Notify/Patterns/NVelocityPatternFormatter.cs
index b36caa7283..4603abb7d7 100644
--- a/common/ASC.Core.Common/Notify/Patterns/NVelocityPatternFormatter.cs
+++ b/common/ASC.Core.Common/Notify/Patterns/NVelocityPatternFormatter.cs
@@ -71,8 +71,7 @@ namespace ASC.Notify.Patterns
 
         private static void EventCartridgeReferenceInsertion(object sender, ReferenceInsertionEventArgs e)
         {
-            var originalString = e.OriginalValue as string;
-            if (originalString == null) return;
+            if (!(e.OriginalValue is string originalString)) return;
             var lines = originalString.Split(new[] { '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries);
             if (lines.Length == 0) return;
             e.NewValue = string.Empty;
diff --git a/common/ASC.Core.Common/Notify/Patterns/Pattern.cs b/common/ASC.Core.Common/Notify/Patterns/Pattern.cs
index 788f4a7ad0..3c2605273c 100644
--- a/common/ASC.Core.Common/Notify/Patterns/Pattern.cs
+++ b/common/ASC.Core.Common/Notify/Patterns/Pattern.cs
@@ -60,8 +60,7 @@ namespace ASC.Notify.Patterns
 
         public override bool Equals(object obj)
         {
-            var p = obj as IPattern;
-            return p != null && p.ID == ID;
+            return obj is IPattern p && p.ID == ID;
         }
 
         public override int GetHashCode()
diff --git a/common/ASC.Core.Common/Notify/Patterns/XmlPatternProvider2.cs b/common/ASC.Core.Common/Notify/Patterns/XmlPatternProvider2.cs
index c87f6736b8..b5896d3700 100644
--- a/common/ASC.Core.Common/Notify/Patterns/XmlPatternProvider2.cs
+++ b/common/ASC.Core.Common/Notify/Patterns/XmlPatternProvider2.cs
@@ -59,8 +59,7 @@ namespace ASC.Notify.Patterns
             var xdoc = new XmlDocument();
             xdoc.LoadXml(xml);
 
-            var xformatter = xdoc.SelectSingleNode("/patterns/formatter") as XmlElement;
-            if (xformatter != null)
+            if (xdoc.SelectSingleNode("/patterns/formatter") is XmlElement xformatter)
             {
                 var type = xformatter.GetAttribute("type");
                 if (!string.IsNullOrEmpty(type))
diff --git a/common/ASC.Core.Common/Notify/Recipients/DirectRecipient.cs b/common/ASC.Core.Common/Notify/Recipients/DirectRecipient.cs
index 9fb2dcd7d2..17c8447f0e 100644
--- a/common/ASC.Core.Common/Notify/Recipients/DirectRecipient.cs
+++ b/common/ASC.Core.Common/Notify/Recipients/DirectRecipient.cs
@@ -77,8 +77,7 @@ namespace ASC.Notify.Recipients
 
         public override bool Equals(object obj)
         {
-            var recD = obj as IDirectRecipient;
-            if (recD == null) return false;
+            if (!(obj is IDirectRecipient recD)) return false;
             return Equals(recD.ID, ID);
         }
 
diff --git a/common/ASC.Core.Common/Notify/Recipients/RecipientsGroup.cs b/common/ASC.Core.Common/Notify/Recipients/RecipientsGroup.cs
index 9d452ee2e1..bef149944a 100644
--- a/common/ASC.Core.Common/Notify/Recipients/RecipientsGroup.cs
+++ b/common/ASC.Core.Common/Notify/Recipients/RecipientsGroup.cs
@@ -48,8 +48,7 @@ namespace ASC.Notify.Recipients
 
         public override bool Equals(object obj)
         {
-            var recGr = obj as IRecipientsGroup;
-            if (recGr == null) return false;
+            if (!(obj is IRecipientsGroup recGr)) return false;
             return Equals(recGr.ID, ID);
         }
 
diff --git a/common/ASC.Core.Common/Security/Authentication/UserAccount.cs b/common/ASC.Core.Common/Security/Authentication/UserAccount.cs
index 3ec64757ea..d45bdf0435 100644
--- a/common/ASC.Core.Common/Security/Authentication/UserAccount.cs
+++ b/common/ASC.Core.Common/Security/Authentication/UserAccount.cs
@@ -71,8 +71,7 @@ namespace ASC.Core.Security.Authentication
 
         public override bool Equals(object obj)
         {
-            var a = obj as IUserAccount;
-            return a != null && ID.Equals(a.ID);
+            return obj is IUserAccount a && ID.Equals(a.ID);
         }
 
         public override int GetHashCode()
diff --git a/common/ASC.Core.Common/Tenants/Tenant.cs b/common/ASC.Core.Common/Tenants/Tenant.cs
index 7d57bc4bed..e31bd5b37e 100644
--- a/common/ASC.Core.Common/Tenants/Tenant.cs
+++ b/common/ASC.Core.Common/Tenants/Tenant.cs
@@ -122,8 +122,7 @@ namespace ASC.Core.Tenants
 
         public override bool Equals(object obj)
         {
-            var t = obj as Tenant;
-            return t != null && t.TenantId == TenantId;
+            return obj is Tenant t && t.TenantId == TenantId;
         }
 
         public override int GetHashCode()
diff --git a/common/ASC.Core.Common/Tenants/TenantQuota.cs b/common/ASC.Core.Common/Tenants/TenantQuota.cs
index d84459f335..2b5b94018d 100644
--- a/common/ASC.Core.Common/Tenants/TenantQuota.cs
+++ b/common/ASC.Core.Common/Tenants/TenantQuota.cs
@@ -211,8 +211,7 @@ namespace ASC.Core.Tenants
 
         public override bool Equals(object obj)
         {
-            var q = obj as TenantQuota;
-            return q != null && q.Id == Id;
+            return obj is TenantQuota q && q.Id == Id;
         }
 
 
diff --git a/common/ASC.Core.Common/Tenants/TenantVersion.cs b/common/ASC.Core.Common/Tenants/TenantVersion.cs
index 5906cfe5a4..29cbe440d6 100644
--- a/common/ASC.Core.Common/Tenants/TenantVersion.cs
+++ b/common/ASC.Core.Common/Tenants/TenantVersion.cs
@@ -57,8 +57,7 @@ namespace ASC.Core
 
         public override bool Equals(object obj)
         {
-            var v = obj as TenantVersion;
-            return v != null && v.Id == Id;
+            return obj is TenantVersion v && v.Id == Id;
         }
 
         public override string ToString()
diff --git a/common/ASC.Core.Common/Tests/Class1.cs b/common/ASC.Core.Common/Tests/Class1.cs
index 6f6bf8fd7a..2358826d90 100644
--- a/common/ASC.Core.Common/Tests/Class1.cs
+++ b/common/ASC.Core.Common/Tests/Class1.cs
@@ -56,8 +56,7 @@ namespace ASC.Common.Tests.Security.Authorizing
 
         public override bool Equals(object obj)
         {
-            var class1 = obj as Class1;
-            return class1 != null && Equals(class1.Id, Id);
+            return obj is Class1 class1 && Equals(class1.Id, Id);
         }
 
         public override int GetHashCode()
diff --git a/common/ASC.Core.Common/Tests/DomainStub.cs b/common/ASC.Core.Common/Tests/DomainStub.cs
index 85a91a49fe..d5ce8a21b3 100644
--- a/common/ASC.Core.Common/Tests/DomainStub.cs
+++ b/common/ASC.Core.Common/Tests/DomainStub.cs
@@ -334,8 +334,7 @@ namespace ASC.Common.Tests.Security.Authorizing
 
             public override bool Equals(object obj)
             {
-                var p = obj as PermissionRecord;
-                return p != null && Id == p.Id;
+                return obj is PermissionRecord p && Id == p.Id;
             }
         }
     }
diff --git a/common/ASC.Data.Storage/DiscStorage/DiscDataStore.cs b/common/ASC.Data.Storage/DiscStorage/DiscDataStore.cs
index 20e0796b31..57287d02a0 100644
--- a/common/ASC.Data.Storage/DiscStorage/DiscDataStore.cs
+++ b/common/ASC.Data.Storage/DiscStorage/DiscDataStore.cs
@@ -145,9 +145,8 @@ namespace ASC.Data.Storage.DiscStorage
             //Copy stream
 
             //optimaze disk file copy
-            var fileStream = buffered as FileStream;
             long fslen;
-            if (fileStream != null && WorkContext.IsMono)
+            if (buffered is FileStream fileStream && WorkContext.IsMono)
             {
                 File.Copy(fileStream.Name, target, true);
                 fslen = fileStream.Length;
diff --git a/common/ASC.MessagingSystem/MessageTarget.cs b/common/ASC.MessagingSystem/MessageTarget.cs
index d96908f02b..71a3e4b194 100644
--- a/common/ASC.MessagingSystem/MessageTarget.cs
+++ b/common/ASC.MessagingSystem/MessageTarget.cs
@@ -40,9 +40,8 @@ namespace ASC.MessagingSystem
             try
             {
                 var res = new List<string>();
-                var ids = value as System.Collections.IEnumerable;
 
-                if (ids != null)
+                if (value is System.Collections.IEnumerable ids)
                 {
                     res.AddRange(from object id in ids select id.ToString());
                 }
diff --git a/web/ASC.Web.Api/Models/QuotaWrapper.cs b/web/ASC.Web.Api/Models/QuotaWrapper.cs
index 1067f4bd8a..00b0f6d892 100644
--- a/web/ASC.Web.Api/Models/QuotaWrapper.cs
+++ b/web/ASC.Web.Api/Models/QuotaWrapper.cs
@@ -107,8 +107,7 @@ namespace ASC.Web.Studio.Core.Quota
                 result.UserStorageSize = CoreContext.Configuration.PersonalMaxSpace;
 
                 var webItem = WebItemManager.Instance[WebItemManager.DocumentsProductID];
-                var spaceUsageManager = webItem.Context.SpaceUsageStatManager as IUserSpaceUsage;
-                if (spaceUsageManager != null)
+                if (webItem.Context.SpaceUsageStatManager is IUserSpaceUsage spaceUsageManager)
                     result.UserUsedSize = spaceUsageManager.GetUserSpaceUsage(SecurityContext.CurrentAccount.ID);
             }
 
diff --git a/web/ASC.Web.Core/NavigationWebItem.cs b/web/ASC.Web.Core/NavigationWebItem.cs
index d92500754a..a20f2dbc10 100644
--- a/web/ASC.Web.Core/NavigationWebItem.cs
+++ b/web/ASC.Web.Core/NavigationWebItem.cs
@@ -58,8 +58,7 @@ namespace ASC.Web.Core
 
         public override bool Equals(object obj)
         {
-            var m = obj as IWebItem;
-            return m != null && ID == m.ID;
+            return obj is IWebItem m && ID == m.ID;
         }
 
         public override int GetHashCode()
diff --git a/web/ASC.Web.Core/Tfa/TfaAppUserSettings.cs b/web/ASC.Web.Core/Tfa/TfaAppUserSettings.cs
index 4ce2071045..229ddfbe6c 100644
--- a/web/ASC.Web.Core/Tfa/TfaAppUserSettings.cs
+++ b/web/ASC.Web.Core/Tfa/TfaAppUserSettings.cs
@@ -106,8 +106,7 @@ namespace ASC.Web.Studio.Core.TFA
 
         public static void DisableForUser(Guid guid)
         {
-            var defaultSettings = new TfaAppUserSettings().GetDefault() as TfaAppUserSettings;
-            if (defaultSettings != null)
+            if (new TfaAppUserSettings().GetDefault() is TfaAppUserSettings defaultSettings)
             {
                 defaultSettings.SaveForUser(guid);
             }
diff --git a/web/ASC.Web.Core/WebItemManager.cs b/web/ASC.Web.Core/WebItemManager.cs
index d380c38c3d..564ed2bbc0 100644
--- a/web/ASC.Web.Core/WebItemManager.cs
+++ b/web/ASC.Web.Core/WebItemManager.cs
@@ -229,8 +229,7 @@ namespace ASC.Web.Core
 
         public Guid GetParentItemID(Guid itemID)
         {
-            var m = this[itemID] as IModule;
-            return m != null ? m.ProjectId : Guid.Empty;
+            return this[itemID] is IModule m ? m.ProjectId : Guid.Empty;
         }
 
         public static int GetSortOrder(IWebItem item)
diff --git a/web/ASC.Web.Core/WebItemSecurity.cs b/web/ASC.Web.Core/WebItemSecurity.cs
index 9d1d0b8a5c..80febe8c60 100644
--- a/web/ASC.Web.Core/WebItemSecurity.cs
+++ b/web/ASC.Web.Core/WebItemSecurity.cs
@@ -370,11 +370,9 @@ namespace ASC.Web.Core
 
             public ISecurityObjectId InheritFrom(ISecurityObjectId objectId)
             {
-                var s = objectId as WebItemSecurityObject;
-                if (s != null)
+                if (objectId is WebItemSecurityObject s)
                 {
-                    var parent = WebItemSecurityObject.Create(WebItemManager.Instance.GetParentItemID(s.WebItemId).ToString("N")) as WebItemSecurityObject;
-                    return parent != null && parent.WebItemId != s.WebItemId && parent.WebItemId != Guid.Empty ? parent : null;
+                    return WebItemSecurityObject.Create(WebItemManager.Instance.GetParentItemID(s.WebItemId).ToString("N")) is WebItemSecurityObject parent && parent.WebItemId != s.WebItemId && parent.WebItemId != Guid.Empty ? parent : null;
                 }
                 return null;
             }
diff --git a/web/ASC.Web.Core/WhiteLabel/AdditionalWhiteLabelSettings.cs b/web/ASC.Web.Core/WhiteLabel/AdditionalWhiteLabelSettings.cs
index 46ca95f9aa..ec97a76ff9 100644
--- a/web/ASC.Web.Core/WhiteLabel/AdditionalWhiteLabelSettings.cs
+++ b/web/ASC.Web.Core/WhiteLabel/AdditionalWhiteLabelSettings.cs
@@ -76,9 +76,7 @@ namespace ASC.Web.Core.WhiteLabel
         {
             get
             {
-                var defaultSettings = GetDefault() as AdditionalWhiteLabelSettings;
-
-                if (defaultSettings == null) return false;
+                if (!(GetDefault() is AdditionalWhiteLabelSettings defaultSettings)) return false;
 
                 return StartDocsEnabled == defaultSettings.StartDocsEnabled &&
                        HelpCenterEnabled == defaultSettings.HelpCenterEnabled &&
diff --git a/web/ASC.Web.Core/WhiteLabel/CompanyWhiteLabelSettings.cs b/web/ASC.Web.Core/WhiteLabel/CompanyWhiteLabelSettings.cs
index 3251883893..ea92bdfa7a 100644
--- a/web/ASC.Web.Core/WhiteLabel/CompanyWhiteLabelSettings.cs
+++ b/web/ASC.Web.Core/WhiteLabel/CompanyWhiteLabelSettings.cs
@@ -58,9 +58,7 @@ namespace ASC.Web.Core.WhiteLabel
         {
             get
             {
-                var defaultSettings = GetDefault() as CompanyWhiteLabelSettings;
-
-                if (defaultSettings == null) return false;
+                if (!(GetDefault() is CompanyWhiteLabelSettings defaultSettings)) return false;
 
                 return CompanyName == defaultSettings.CompanyName &&
                        Site == defaultSettings.Site &&
diff --git a/web/ASC.Web.Core/WhiteLabel/MailWhiteLabelSettings.cs b/web/ASC.Web.Core/WhiteLabel/MailWhiteLabelSettings.cs
index 69e662c330..966262a07c 100644
--- a/web/ASC.Web.Core/WhiteLabel/MailWhiteLabelSettings.cs
+++ b/web/ASC.Web.Core/WhiteLabel/MailWhiteLabelSettings.cs
@@ -61,9 +61,7 @@ namespace ASC.Web.Core.WhiteLabel
         {
             get
             {
-                var defaultSettings = GetDefault() as MailWhiteLabelSettings;
-
-                if (defaultSettings == null) return false;
+                if (!(GetDefault() is MailWhiteLabelSettings defaultSettings)) return false;
 
                 return FooterEnabled == defaultSettings.FooterEnabled &&
                        FooterSocialEnabled == defaultSettings.FooterSocialEnabled &&