// Creates the three canonical null guard conditions.
private static Expression CreateNullGuardBlockExpression <TProperty>(AutoEqualityPropertyContext context, LabelTarget labelTarget)
{
var areEqualExpression = CreateIfThenExpression <TProperty, bool>(context, labelTarget, (left, right) => ReferenceEquals(left, right), true);
var leftIsNullExpression = CreateIfThenExpression <TProperty, bool>(context, labelTarget, (left, right) => ReferenceEquals(left, null), false);
var rightIsNullExpression = CreateIfThenExpression <TProperty, bool>(context, labelTarget, (left, right) => ReferenceEquals(left, null), false);
return(Expression.Block(
areEqualExpression,
leftIsNullExpression,
rightIsNullExpression
));
}
public static Expression CreateEqualsExpression <TProperty>(AutoEqualityPropertyContext context)
{
var labelTarget = Expression.Label(typeof(bool));
var nullGuardBlockExpression = CreateNullGuardBlockExpression <TProperty>(context, labelTarget);
var equalsMethodExpression = CreateEqualsMethodExpression <TProperty>(context);
return(Expression.Block(new[]
{
nullGuardBlockExpression,
Expression.Return(labelTarget, equalsMethodExpression),
Expression.Label(labelTarget, defaultValue: Expression.Constant(false))
}));
}
private static Expression CreateIfThenExpression <TProperty, TResult>(AutoEqualityPropertyContext context, LabelTarget labelTarget, Func <TProperty, TProperty, bool> referenceEquals, TResult result)
{
// Let the compiler create this expression for us.
var referenceEquasExpression = (Expression <Func <TProperty, TProperty, bool> >)((left, right) => referenceEquals(left, right));
var referenceEquasInvokeExpression = Expression.Invoke(
referenceEquasExpression,
Expression.Property(context.LeftParameter, context.Property),
Expression.Property(context.RightParameter, context.Property)
);
return(Expression.IfThen(
referenceEquasInvokeExpression,
Expression.Return(labelTarget, Expression.Constant(result))
));
}
// The 'rightParameter' argument is not used but by having the same signature for both methods allows for a few optimizations in other places.
public static Expression CreateGetHashCodeExpression <TProperty>(AutoEqualityPropertyContext context)
{
if (HasDefaultComparer(context.Property.PropertyType))
{
// Short-cut to have compiler write this expression for us.
//var getHashCodeFunc = (Expression<Func<TProperty, int>>)((obj) => ReferenceEquals(obj, null) ? 0 : GetComparer<TProperty>(context.Attribute).GetHashCode(obj));
var getHashCodeFunc = (Expression <Func <TProperty, int> >)((obj) => GetComparer <TProperty>(context.Attribute).GetHashCode(obj));
return(Expression.Invoke(
getHashCodeFunc,
Expression.Property(context.LeftParameter, context.Property)
));
}
else
{
// Call the instance 'GetHashCode' method by default.
var labelTarget = Expression.Label(typeof(int));
//var getHashCodeNullGuardExpression = CreateGetHashCodeNullGuardExpression<TProperty>(context, labelTarget);
//var getHashCodeMethod = context.Property.PropertyType.GetMethod(nameof(GetHashCode));
var getHashCodeFunc = (Expression <Func <TProperty, int> >)((obj) => ReferenceEquals(obj, null) ? 0 : obj.GetHashCode());
return(Expression.Invoke(
getHashCodeFunc,
Expression.Property(context.LeftParameter, context.Property)
));
}
// ReSharper disable once AssignNullToNotNullAttribute - getHashCodeMethod is never null
//var getHashCodeExpression = Expression.Call(
// Expression.Property(context.LeftParameter, context.Property),
// getHashCodeMethod
//);
//return Expression.Block(new[]
//{
// getHashCodeNullGuardExpression,
// Expression.Return(labelTarget, getHashCodeExpression),
// Expression.Label(labelTarget, defaultValue: Expression.Constant(0))
//});
}
private static Expression CreateEqualsMethodExpression <TProperty>(AutoEqualityPropertyContext context)
{
if (HasDefaultComparer(context.Property.PropertyType))
{
// Short-cut to have compiler write this expression for us.
var equalsFunc = (Expression <Func <TProperty, TProperty, bool> >)((x, y) => GetComparer <TProperty>(context.Attribute).Equals(x, y));
return(Expression.Invoke(
equalsFunc,
Expression.Property(context.LeftParameter, context.Property),
Expression.Property(context.RightParameter, context.Property)
));
}
var equalsMethod = GetEqualsMethod(context.Property.PropertyType);
return(Expression.Call(
Expression.Property(context.LeftParameter, context.Property),
equalsMethod,
Expression.Property(context.RightParameter, context.Property)
));
}
private static Expression CreateGetHashCodeNullGuardExpression <TProperty>(AutoEqualityPropertyContext context, LabelTarget labelTarget)
{
var propertyIsNullExpression = CreateIfThenExpression <TProperty, int>(labelTarget, (left, right) => ReferenceEquals(left, right), context.LeftParameter, Expression.Constant(null, typeof(TProperty)), 0);
return(Expression.Block(propertyIsNullExpression));
}