public static Expression ForEach(ParameterExpression item, Expression source, Expression body)
{
if (!typeof(IEnumerable).IsAssignableFrom(source.Type))
{
throw new InvalidOperationException($"{source.Type} does not implement IEnumerable and cannot be iterated using foreach");
}
ParameterExpression enumerator = Expression.Parameter(typeof(IEnumerator), "enumerator");
LabelTarget forEachEnd = Expression.Label();
return(Expression.Block(
new[] { item, enumerator },
Expression.Assign(
enumerator,
Expression.Call(source, EnumerableMembers.GetEnumerator())
),
Expression.Loop(
Expression.IfThenElse(
Expression.Call(enumerator, EnumerableMembers.MoveNext()),
Expression.Block(
Expression.Assign(item, Expression.Convert(Expression.Property(enumerator, EnumerableMembers.Current()), item.Type)),
body
),
Expression.Break(forEachEnd)
),
forEachEnd
)
));
}
private Expression MoveEnumerator(ParameterExpression enumerator, ParameterExpression someLeft)
{
return(Expression.Assign(
someLeft,
Expression.Call(
enumerator,
EnumerableMembers.MoveNext(typeof(IDiffItem))
)
));
}