protected override Expression <Func <TFrom, TTo, bool> > CompileToExpression()
{
var from = Expression.Parameter(typeof(IEnumerable <>).MakeGenericType(EnumerableReflection <TFrom> .ItemType), "from");
var to = Expression.Parameter(typeof(IEnumerable <>).MakeGenericType(EnumerableReflection <TTo> .ItemType), "to");
var fromEnumeratorVariable = Expression.Parameter(typeof(IEnumerator <>).MakeGenericType(EnumerableReflection <TFrom> .ItemType), "fromEnumerator");
var toEnumeratorVariable = Expression.Parameter(typeof(IEnumerator <>).MakeGenericType(EnumerableReflection <TTo> .ItemType), "toEnumerator");
var hasFromVariable = Expression.Parameter(typeof(bool), "hasFrom");
var hasToVariable = Expression.Parameter(typeof(bool), "hasTo");
var end = Expression.Label(typeof(bool));
Expression nullHandling;
if (this.aMapNullToEmpty)
{
nullHandling = Expression.IfThen(
Expression.Equal(from, Expression.Constant(null, from.Type)),
Expression.Return(
end,
Expression.Not(
Expression.Call(LinqMethods.Any(EnumerableReflection <TTo> .ItemType), to)
)
)
);
}
else
{
nullHandling = Expression.Empty();
}
return(Expression.Lambda <Func <TFrom, TTo, bool> >(
Expression.Block(
new[] { fromEnumeratorVariable, toEnumeratorVariable, hasFromVariable, hasToVariable },
nullHandling,
Expression.Assign(fromEnumeratorVariable, Expression.Call(from, EnumerableMethods.GetEnumerable(EnumerableReflection <TFrom> .ItemType))),
Expression.Assign(toEnumeratorVariable, Expression.Call(to, EnumerableMethods.GetEnumerable(EnumerableReflection <TTo> .ItemType))),
Expression.Loop(
Expression.Block(
Expression.Assign(hasFromVariable, Expression.Call(fromEnumeratorVariable, EnumerableMethods.MoveNext(EnumerableReflection <TFrom> .ItemType))),
Expression.Assign(hasToVariable, Expression.Call(toEnumeratorVariable, EnumerableMethods.MoveNext(EnumerableReflection <TTo> .ItemType))),
Expression.IfThen(
Expression.AndAlso(
Expression.Not(hasFromVariable),
Expression.Not(hasToVariable)
),
Expression.Return(end, Expression.Constant(true))
),
Expression.IfThen(
Expression.OrElse(
Expression.Not(hasFromVariable),
Expression.Not(hasToVariable)
),
Expression.Return(end, Expression.Constant(false))
),
Expression.IfThen(
Expression.Not(
this.CreateItemEqualityExpression(
Expression.Property(fromEnumeratorVariable, EnumerableMethods.Current(EnumerableReflection <TFrom> .ItemType)),
Expression.Property(toEnumeratorVariable, EnumerableMethods.Current(EnumerableReflection <TTo> .ItemType))
)
),
Expression.Return(end, Expression.Constant(false))
)
)
),
Expression.Label(end, Expression.Constant(true))
),
from, to
));
}