Getting error “The parameter was not bound in the specified LINQ to Entities query expression.”

问题

I am trying to create a generic way to find deals that have a date that fall within a list of user-specified date ranges. Here's my code:

var closeDates = new List<Range<DateTime>>
    {{ new Range<DateTime>{ Start = DateTime.Now, End = DateTime.Now.AddDays(1) }};

var deals = dbContext.Deals.AsQueryable();
deals = _helperService.ApplyDateRanges(deals, deal => deal.ClosedDate, closeDates);

The _helperService method:

public IQueryable<T> ApplyDateRanges<T>(IQueryable<T> query, Expression<Func<T, DateTime>> dateSelector, IEnumerable<Range<DateTime>> dates)
{
    var enumerable = dates as Range<DateTime>[] ?? dates.ToArray();

    Expression<Func<T, Range<DateTime>, bool>> matcher =
        (row, rangeItem) => (rangeItem.Start == null || dateSelector.Invoke(row) >= rangeItem.Start) &&
                            (rangeItem.End == null || dateSelector.Invoke(row) < rangeItem.End.Value.AddDays(1));

    var expr = PredicateBuilder.False<T>();
    foreach (var dt in enumerable)
    {
        expr = expr.Or(d => matcher.Invoke(d, dt));
    }
    return query.AsExpandable().Where(expr.Expand());
}

But I'm getting the error: The parameter 'deal' was not bound in the specified LINQ to Entities query expression. What is causing this?

回答1:

The exception message indicates that the dateSelector parameter has not been rebound correctly. Since there is third party package involved, I can't tell what is causing it.

But I guess this is related to your previous question. I was going to suggest you another simple manual expression building based working solution not involving third party packages. And here it is (assuming Range class Start/End members are of type DateTime?):

public static class QueryableExtensions
{
    public static IQueryable<T> WhereIn<T>(IQueryable<T> source, Expression<Func<T, DateTime>> dateSelector, IEnumerable<Range<DateTime>> ranges)
    {
        var filter = ranges == null ? null : ranges.Select(range =>
        {
            var startFilter = range.Start != null ? Expression.GreaterThanOrEqual(dateSelector.Body, Expression.Constant(range.Start.Value.Date)) : null;
            var endFilter = range.End != null ? Expression.LessThan(dateSelector.Body, Expression.Constant(range.End.Value.Date.AddDays(1))) : null;
            return startFilter == null ? endFilter : endFilter == null ? startFilter : Expression.AndAlso(startFilter, endFilter);
        })
        .Where(item => item != null)
        .Aggregate(Expression.OrElse);
        return filter != null ? source.Where(Expression.Lambda<Func<T, bool>>(filter, dateSelector.Parameters[0])) : source;
    }
}

and you can use it simply like this (no helper service instance needed, following LINQ spirit):

var deals = dbContext.Deals.WhereIn(deal => deal.ClosedDate, closeDates);

来源：https://stackoverflow.com/questions/36722610/getting-error-the-parameter-was-not-bound-in-the-specified-linq-to-entities-que