private static Expression EqualityExpr(Expression oneParam, Expression otherParam, string memberName, Type memberType,
GetMemberAccessor getMemberAccessor)
{
if (memberType.IsGenericType && ValidSequenceTypes.Contains(memberType.GetGenericTypeDefinition()))
{
return(SequenceEqualsExpr(oneParam, otherParam, memberName, memberType.GenericTypeArguments.Single(), getMemberAccessor));
}
if (memberType.IsValueType || ValueTypeEquivalents.Contains(memberType))
{
return(EqualOperatorExpr(oneParam, otherParam, memberName, getMemberAccessor));
}
if (memberType.GetInterfaces().Any(i =>
i.IsGenericType &&
i.GetGenericTypeDefinition() == typeof(IEquatable <>) &&
i.GenericTypeArguments.Single() == memberType))
{
return
(Expression.OrElse(
EqualOperatorExpr(oneParam, otherParam, memberName, getMemberAccessor),
Expression.AndAlso(
Expression.Not(
Expression.ExclusiveOr(
Expression.Equal(
getMemberAccessor(oneParam, memberName),
Expression.Constant(null)),
Expression.Equal(
getMemberAccessor(otherParam, memberName),
Expression.Constant(null)))),
EqualsExpr(oneParam, otherParam, memberName, memberType, getMemberAccessor))));
}
throw new ArgumentException($"cannot handle field {memberName} of type {memberType.FullName}");
}
private static Func <T, T, bool> ForMembers <T, TMember>(
IEnumerable <TMember> memberInfos,
Func <TMember, Type> getMemberType,
GetMemberAccessor getMemberAccessor)
where TMember : MemberInfo
{
ParameterExpression oneParam = Expression.Parameter(typeof(T), "one");
ParameterExpression otherParam = Expression.Parameter(typeof(T), "other");
if (!memberInfos.Any())
{
return(Expression.Lambda <Func <T, T, bool> >(
Expression.Constant(true),
oneParam,
otherParam)
.Compile());
}
var equalityExpressions = memberInfos.Select(memberInfo =>
EqualityExpr(oneParam, otherParam, memberInfo.Name, getMemberType(memberInfo), getMemberAccessor));
var andExpression = equalityExpressions.Aggregate(Expression.AndAlso);
Expression <Func <T, T, bool> > equalsExpression = Expression.Lambda <Func <T, T, bool> >(
andExpression,
new[] { oneParam, otherParam });
return(equalsExpression.Compile());
}
private static Expression EqualityExpr(Expression oneParam, Expression otherParam, string memberName, Type memberType,
GetMemberAccessor getMemberAccessor)
{
if (memberType.IsValueType || ValueTypeEquivalents.Contains(memberType))
{
// one == other
return(EqualOperatorExpr(oneParam, otherParam, memberName, getMemberAccessor));
}
if (memberType.GetInterfaces().Any(i =>
i.IsGenericType &&
i.GetGenericTypeDefinition() == typeof(IEquatable <>) &&
i.GenericTypeArguments.Single() == memberType))
{
// one == null ? other == null : one.Equals(other)
return
(Condition(
Equal(
getMemberAccessor(oneParam, memberName),
Constant(null)),
Equal(
getMemberAccessor(otherParam, memberName),
Constant(null)),
TypedEqualsExpr(oneParam, otherParam, memberName, memberType, getMemberAccessor)));
}
if (new[] { memberType }.Concat(memberType.GetInterfaces()).FirstOrDefault(i =>
i.IsGenericType &&
i.GetGenericTypeDefinition() == typeof(IEnumerable <>)) is Type firstEnumerableType)
{
// (one == null && other == null) || (one != null && other != null && Enumerable.SequenceEquals(one, other))
return
(OrElse(
AndAlso(
Equal(
getMemberAccessor(oneParam, memberName),
Constant(null)),
Equal(
getMemberAccessor(otherParam, memberName),
Constant(null))),
AndAlso(
AndAlso(
NotEqual(
getMemberAccessor(oneParam, memberName),
Constant(null)),
NotEqual(
getMemberAccessor(otherParam, memberName),
Constant(null))),
SequenceEqualsExpr(oneParam, otherParam, memberName, firstEnumerableType.GetGenericArguments().Single(), getMemberAccessor))));
}
return(ObjectEqualsExpression(oneParam, otherParam, memberName, getMemberAccessor));
}
private static MethodCallExpression SequenceEqualsExpr(
Expression oneParam, Expression otherParam, string memberName, Type elementType, GetMemberAccessor getMemberAccessor)
{
var enumerableType = typeof(IEnumerable <>).MakeGenericType(elementType);
return(Expression.Call(
null,
Methods.SequenceEqual(elementType),
Expression.Convert(
getMemberAccessor(oneParam, memberName), enumerableType),
Expression.Convert(
getMemberAccessor(otherParam, memberName), enumerableType)));
}
private static BinaryExpression EqualOperatorExpr(
Expression oneParam, Expression otherParam, string fieldName, GetMemberAccessor getMemberAccessor) =>
Expression.Equal(
getMemberAccessor(oneParam, fieldName),
getMemberAccessor(otherParam, fieldName));
private static MethodCallExpression EqualsExpr(
Expression oneParam, Expression otherParam, string memberName, Type memberType, GetMemberAccessor getMemberAccessor) =>
Expression.Call(
getMemberAccessor(oneParam, memberName),
Methods.EquatableEquals(memberType),
getMemberAccessor(otherParam, memberName));
private static MethodCallExpression ObjectEqualsExpression
(Expression oneParam, Expression otherParam, string memberName, GetMemberAccessor getMemberAccessor) =>
Call(
Methods.ObjectEquals,
getMemberAccessor(oneParam, memberName),
getMemberAccessor(otherParam, memberName));