Reduce cast usage for aggregate functions (#2036)

Co-authored-by: Alexander Zaytsev <alexzaytsev2019@gmail.com>

Author: maca88

src/NHibernate.DomainModel/FooComponent.cs

@@ -92,6 +92,8 @@ public Int32 Count
 			set { _count = value; }
 		}
 
+		public int NotMapped { get; set; }
+
 		public DateTime[] ImportantDates
 		{
 			get { return _importantDates; }

src/NHibernate.DomainModel/NHSpecific/NullableInt32.cs

@@ -7,7 +7,7 @@ namespace NHibernate.DomainModel.NHSpecific
 	/// A nullable type that wraps an <see cref="Int32"/> value.
 	/// </summary>
 	[TypeConverter(typeof(NullableInt32Converter)), Serializable()]
-	public struct NullableInt32 : IFormattable, IComparable
+	public struct NullableInt32 : IFormattable, IComparable, IConvertible
 	{
 		public static readonly NullableInt32 Default = new NullableInt32();
 
@@ -234,5 +234,94 @@ public static NullableInt32 Parse(string s)
 		// TODO: implement the rest of the Parse overloads found in Int32
 
 		#endregion
+
+		#region IConvertible
+
+		public TypeCode GetTypeCode()
+		{
+			return _value.GetTypeCode();
+		}
+
+		public bool ToBoolean(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToBoolean(provider);
+		}
+
+		public char ToChar(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToChar(provider);
+		}
+
+		public sbyte ToSByte(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToSByte(provider);
+		}
+
+		public byte ToByte(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToByte(provider);
+		}
+
+		public short ToInt16(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToInt16(provider);
+		}
+
+		public ushort ToUInt16(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToUInt16(provider);
+		}
+
+		public int ToInt32(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToInt32(provider);
+		}
+
+		public uint ToUInt32(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToUInt32(provider);
+		}
+
+		public long ToInt64(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToInt64(provider);
+		}
+
+		public ulong ToUInt64(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToUInt64(provider);
+		}
+
+		public float ToSingle(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToSingle(provider);
+		}
+
+		public double ToDouble(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToDouble(provider);
+		}
+
+		public decimal ToDecimal(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToDecimal(provider);
+		}
+
+		public DateTime ToDateTime(IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToDateTime(provider);
+		}
+
+		public string ToString(IFormatProvider provider)
+		{
+			return _value.ToString(provider);
+		}
+
+		public object ToType(System.Type conversionType, IFormatProvider provider)
+		{
+			return ((IConvertible) _value).ToType(conversionType, provider);
+		}
+
+		#endregion
 	}
 }

src/NHibernate.DomainModel/Northwind/Entities/Address.cs

@@ -61,6 +61,8 @@ public string Fax
             get { return _fax; }
         }
 
+		public int NotMapped => 1;
+
         public static bool operator ==(Address address1, Address address2)
         {
             if (!ReferenceEquals(address1, null) &&
@@ -114,4 +116,4 @@ public override int GetHashCode()
                 (_fax ?? string.Empty).GetHashCode();
         }
     }
-}
+}

src/NHibernate.DomainModel/Northwind/Entities/IEntity.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace NHibernate.DomainModel.Northwind.Entities
+{
+	public interface IEntity<TId>
+	{
+		TId Id { get; set; }
+	}
+
+	public interface IEntity : IEntity<int>
+	{
+	}
+}

src/NHibernate.DomainModel/Northwind/Entities/Product.cs

@@ -103,9 +103,11 @@ public virtual float ShippingWeight
 			set { _shippingWeight = value; }
 		}
 
+		public virtual int NotMapped => 1;
+
 		public virtual ReadOnlyCollection<OrderLine> OrderLines
 		{
 			get { return new ReadOnlyCollection<OrderLine>(_orderLines); }
 		}
 	}
-}
+}

src/NHibernate.DomainModel/Northwind/Entities/User.cs

@@ -28,7 +28,7 @@ public interface IUser
 		EnumStoredAsInt32 Enum2 { get; set; }
 	}
 
-	public class User : IUser
+	public class User : IUser, IEntity
 	{
 		public virtual int Id { get; set; }
 
@@ -50,6 +50,10 @@ public class User : IUser
 
 		public virtual EnumStoredAsInt32 Enum2 { get; set; }
 
+		public virtual int NotMapped { get; set; }
+
+		public virtual Role NotMappedRole { get; set; }
+
 		public User() { }
 
 		public User(string name, DateTime registeredAt)

src/NHibernate.Test/Async/Linq/SelectionTests.cs

@@ -11,7 +11,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using NHibernate.DomainModel.NHSpecific;
 using NHibernate.DomainModel.Northwind.Entities;
+using NHibernate.Type;
 using NUnit.Framework;
 using NHibernate.Linq;
 
@@ -307,6 +309,10 @@ public async Task CanProjectWithCastAsync()
 
 			var names5 = await (db.Users.Select(p => new { p1 = (p as IUser).Name }).ToListAsync());
 			Assert.AreEqual(3, names5.Count);
+
+			var names6 = await (db.Users.Select(p => new { p1 = (long) p.Id }).ToListAsync());
+			Assert.AreEqual(3, names6.Count);
+
 			// ReSharper restore RedundantCast
 		}
 
@@ -453,6 +459,23 @@ public async Task CanSelectConditionalObjectAsync()
 			Assert.That(fatherIsKnown, Has.Exactly(1).With.Property("FatherIsKnown").True);
 		}
 
+		[Test]
+		public async Task CanCastToDerivedTypeAsync()
+		{
+			var dogs = await (db.Animals
+			                      .Where(a => ((Dog) a).Pregnant)
+			                      .Select(a => new {a.SerialNumber})
+			                      .ToListAsync());
+			Assert.That(dogs, Has.Exactly(1).With.Property("SerialNumber").Not.Null);
+		}
+
+		[Test]
+		public async Task CanCastToCustomRegisteredTypeAsync()
+		{
+			TypeFactory.RegisterType(typeof(NullableInt32), new NullableInt32Type(), Enumerable.Empty<string>());
+			Assert.That(await (db.Users.Where(o => (NullableInt32) o.Id == 1).ToListAsync()), Has.Count.EqualTo(1));
+		}
+
 		public class Wrapper<T>
 		{
 			public T item;