Refactor to use C#7 'is null' operator

Author: SergeiPavlov

Extensions/Xtensive.Orm.BulkOperations/Internals/QueryOperation.cs

@@ -142,14 +142,14 @@ private void JoinViaIn(SqlStatement statement, SqlSelect select)
         var s = (SqlSelect) select.Clone();
         foreach (var column in columns) {
           var ex = SqlDml.Equals(s.From.Columns[column.Name], table.Columns[column.Name]);
-          s.Where = s.Where.IsNullReference() ? ex : SqlDml.And(s.Where, ex);
+          s.Where = s.Where is null ? ex : SqlDml.And(s.Where, ex);
         }
         var existingColumns = s.Columns.ToChainedBuffer();
         s.Columns.Clear();
         var columnToAdd = existingColumns.First(c => c.Name.Equals(columnInfo.Name, StringComparison.Ordinal));
         s.Columns.Add(columnToAdd);
         var @in = SqlDml.In(SqlDml.TableColumn(table, columnInfo.Name), s);
-        where = where.IsNullReference() ? @in : SqlDml.And(where, @in);
+        where = where is null ? @in : SqlDml.And(where, @in);
         columns.Add(columnInfo);
       }
 

Extensions/Xtensive.Orm.Security/Permission.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2011 Xtensive LLC.
+// Copyright (C) 2011 Xtensive LLC.
 // All rights reserved.
 // For conditions of distribution and use, see license.
 // Created by: Dmitri Maximov
@@ -41,15 +41,15 @@ public abstract class Permission
     /// <inheritdoc/>
     public bool Equals(Permission other)
     {
-      if (ReferenceEquals(null, other)) return false;
+      if (other is null) return false;
       if (ReferenceEquals(this, other)) return true;
       return Equals(other.Type, Type) && other.CanRead.Equals(CanRead) && other.CanWrite.Equals(CanWrite) && Equals(other.Query, Query);
     }
 
     /// <inheritdoc/>
     public override bool Equals(object obj)
     {
-      if (ReferenceEquals(null, obj)) return false;
+      if (obj is null) return false;
       if (ReferenceEquals(this, obj)) return true;
       if (obj.GetType() != typeof (Permission)) return false;
       return Equals((Permission) obj);

Orm/Xtensive.Orm.MySql/Sql.Drivers.MySql/v5_0/Compiler.cs

@@ -190,12 +190,12 @@ public override void Visit(SqlFunctionCall node)
     /// <inheritdoc/>
     protected override void VisitSelectLimitOffset(SqlSelect node)
     {
-      if (!node.Limit.IsNullReference()) {
+      if (node.Limit is not null) {
         AppendTranslated(node, SelectSection.Limit);
         node.Limit.AcceptVisitor(this);
       }
-      if (!node.Offset.IsNullReference()) {
-        if (node.Limit.IsNullReference()) {
+      if (node.Offset is not null) {
+        if (node.Limit is null) {
           AppendTranslated(node, SelectSection.Limit);
           _ = context.Output.Append(" 18446744073709551615 "); // magic number from http://dev.mysql.com/doc/refman/5.0/en/select.html
         }

Orm/Xtensive.Orm.PostgreSql/Sql.Drivers.PostgreSql/v8_0/Compiler.cs

@@ -31,7 +31,7 @@ public override void Visit(SqlDeclareCursor node)
     public override void Visit(SqlBinary node)
     {
       var right = node.Right as SqlArray;
-      if (!right.IsNullReference() && (node.NodeType is SqlNodeType.In or SqlNodeType.NotIn)) {
+      if (right is not null && (node.NodeType is SqlNodeType.In or SqlNodeType.NotIn)) {
         var row = SqlDml.Row(right.GetValues().Select(value => SqlDml.Literal(value)).ToArray());
         base.Visit(node.NodeType == SqlNodeType.In ? SqlDml.In(node.Left, row) : SqlDml.NotIn(node.Left, row));
       }

Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/Compiler.cs

@@ -75,7 +75,7 @@ public override void Visit(SqlUpdate node)
     /// <inheritdoc/>
     protected override void VisitUpdateLimit(SqlUpdate node)
     {
-      if (!node.Limit.IsNullReference()) {
+      if (node.Limit is not null) {
         if (!Driver.ServerInfo.Query.Features.Supports(QueryFeatures.UpdateLimit)) {
           throw new NotSupportedException(Strings.ExStorageDoesNotSupportLimitationOfRowCountToUpdate);
         }
@@ -104,7 +104,7 @@ public override void Visit(SqlDelete node)
     /// <inheritdoc/>
     protected override void VisitDeleteLimit(SqlDelete node)
     {
-      if (!node.Limit.IsNullReference()) {
+      if (node.Limit is not null) {
         if (!Driver.ServerInfo.Query.Features.Supports(QueryFeatures.DeleteLimit)) {
           throw new NotSupportedException(Strings.ExStorageDoesNotSupportLimitationOfRowCountToDelete);
         }
@@ -287,12 +287,12 @@ public override void Visit(SqlRound node)
       var shouldCastToDecimal = node.Type==TypeCode.Decimal;
       switch (node.Mode) {
         case MidpointRounding.ToEven:
-          result = node.Length.IsNullReference()
+          result = node.Length is null
             ? BankersRound(node.Argument, shouldCastToDecimal)
             : BankersRound(node.Argument, node.Length, shouldCastToDecimal);
           break;
         case MidpointRounding.AwayFromZero:
-          result = node.Length.IsNullReference()
+          result = node.Length is null
             ? RegularRound(node.Argument, shouldCastToDecimal)
             : RegularRound(node.Argument, node.Length, shouldCastToDecimal);
           break;

Orm/Xtensive.Orm.Tests.Core/Modelling/IndexingModel/TypeInfo.cs

@@ -75,7 +75,7 @@ public object Clone()
 
     public bool Equals(TypeInfo other)
     {
-      if (ReferenceEquals(null, other))
+      if (other is null)
         return false;
       if (ReferenceEquals(this, other))
         return true;
@@ -90,7 +90,7 @@ public bool Equals(TypeInfo other)
     /// <inheritdoc/>
     public override bool Equals(object obj)
     {
-      if (ReferenceEquals(null, obj))
+      if (obj is null)
         return false;
       if (ReferenceEquals(this, obj))
         return true;

Orm/Xtensive.Orm.Tests.Sql/CloneTests.cs

@@ -378,7 +378,7 @@ public void SqlSelectCloneTest()
         Assert.AreNotEqual(s.From, sClone.From);
         Assert.AreEqual(s.From.NodeType, sClone.From.NodeType);
       }
-      if (!s.Having.IsNullReference()) {
+      if (s.Having is not null) {
         Assert.AreNotEqual(s.Having, sClone.Having);
         Assert.AreEqual(s.Having.NodeType, sClone.Having.NodeType);
       }
@@ -431,7 +431,7 @@ public void SqlSelectCloneTest()
       for (int i = 0, l = s.OrderBy.Count; i < l; i++) {
         Assert.AreNotEqual(s.OrderBy[i], sClone.OrderBy[i]);
         Assert.AreEqual(s.OrderBy[i].Ascending, sClone.OrderBy[i].Ascending);
-        if (s.OrderBy[i].Expression.IsNullReference())
+        if (s.OrderBy[i].Expression is null)
           Assert.AreEqual(s.OrderBy[i].Expression, sClone.OrderBy[i].Expression);
         else
           Assert.AreNotEqual(s.OrderBy[i].Expression, sClone.OrderBy[i].Expression);
@@ -550,7 +550,7 @@ public void SqlDeleteCloneTest()
       Assert.AreNotEqual(d.Delete, dClone.Delete);
       Assert.AreEqual(d.NodeType, dClone.NodeType);
       Assert.AreEqual(d.Hints.Count, dClone.Hints.Count);
-      if (!d.Where.IsNullReference()) {
+      if (d.Where is not null) {
         Assert.AreNotEqual(d.Where, dClone.Where);
         Assert.AreEqual(d.Where.NodeType, dClone.Where.NodeType);
       }

Orm/Xtensive.Orm.Tests.Sql/Firebird/IndexTest.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2003-2010 Xtensive LLC.
+// Copyright (C) 2003-2010 Xtensive LLC.
 // All rights reserved.
 // For conditions of distribution and use, see license.
 // Created by: Csaba Beer
@@ -61,7 +61,7 @@ public override void CreateExpressionIndexTest()
       Assert.IsNotNull(i2);
       Assert.AreEqual(1, i2.Columns.Count);
 
-      Assert.IsTrue(!i2.Columns[0].Expression.IsNullReference());
+      Assert.IsTrue(i2.Columns[0].Expression is not null);
     }
 
     [Test, Ignore("Test is not implemented")]

Orm/Xtensive.Orm.Tests.Sql/IndexTest.cs

@@ -70,7 +70,7 @@ public virtual void CreateFilteredIndexTest()
       var i2 = t2.Indexes[FilteredIndexName];
       Assert.IsNotNull(i2);
       Assert.AreEqual(2, i2.Columns.Count);
-      Assert.IsTrue(!i2.Where.IsNullReference());
+      Assert.IsTrue(i2.Where is not null);
     }
   }
 }

Orm/Xtensive.Orm.Tests.Sql/MySQL/MiscTests.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2003-2010 Xtensive LLC.
+// Copyright (C) 2003-2010 Xtensive LLC.
 // All rights reserved.
 // For conditions of distribution and use, see license.
 // Created by: Malisa Ncube
@@ -42,10 +42,10 @@ public void BinaryExpressionTest()
     {
       SqlLiteral<int> l = SqlDml.Literal(1);
       bool passed = false;
-      if (!l.IsNullReference())
+      if (l is not null)
         passed = true;
       Assert.IsTrue(passed);
-      if (l.IsNullReference())
+      if (l is null)
         passed = false;
       Assert.IsTrue(passed);
     }