Map Dynamic Linq Expression

Question

public static IQueryable<T> FilterExact<T>(this IQueryable<T> details, int c, Func<T, int> lambda)
{
    if (c > 0)
    {
        details = details.Where(s => lambda(s).Equals(c));
    }
    return details;
}

The above is what I have so far. The current error exist due to linq to entity error, which can be fixed by switching it to IEnumerable, but instead, what I want is to be able to make a new linq Expression, instead of executing the function directly.

How would I go about doing this? I would prefer mapping from Func<T, int> to Expression<Func<T, bool>>.

The reason I need this is because there are a few places where code just as below exist, except the same code is copy-pasted multiple times with a different entity column associated. I want to create this as a method to prevent code duplication, but need a way to specify which column to use. (I first tried reflection, but it slowed everything down significantly.)

if (!string.IsNullOrEmpty(searchCriteria.StudyDate))
{
    if (searchCriteria.StudyDate.Contains(":"))
    {
        string[] dates = searchCriteria.StudyDate.Split(':');
        DateTime startDate;
        DateTime endDate;
        DateTime.TryParse(dates[0], out startDate);
        DateTime.TryParse(dates[1], out endDate);
        if (startDate.Year > 1 && endDate.Year > 1 && endDate > startDate)
        {
            dropChargesStudies = dropChargesStudies.Where(s => s.PERFORMED >= startDate && s.PERFORMED <= endDate);
        }
        else
        {
            throw new Exception("The study date is invalid.");
        }
    }
    else
    {
        DateTime studyDateParsed;
        DateTime.TryParse(searchCriteria.StudyDate, out studyDateParsed);
        if (studyDateParsed.Year > 1)
        {
            dropChargesStudies = dropChargesStudies.Where(s => s.PERFORMED.Value == studyDateParsed);
        }
        else
        {
            throw new Exception("The study date is invalid.");
        }
    }
}

Possible duplicate of [converting a .net Func to a .net Expression>](http://stackoverflow.com/questions/767733/converting-a-net-funct-to-a-net-expressionfunct) — Grundy, Nov 13 '15 at 18:00
Do you really need this? Can't you just change your method signature to receive `Expression` methods do. — Ivan Stoev, Nov 13 '15 at 18:02
Yes I do. I'm trying to make something a little more complicated than above, and it will be used multiple times. — Joseph Whitley, Nov 13 '15 at 18:19
Then what are you are trying to do is wrong from the beginning. Good luck. — Ivan Stoev, Nov 13 '15 at 19:43
@JosephWhitley Nothing about that example explains why you can't accept an expression. If you don't accept an expression then it's simply impossible. Period. — Servy, Nov 13 '15 at 20:54
@JosephWhitley Accept an `Expression`, rather than a delegate, as Joe Ivan said. — Servy, Nov 13 '15 at 21:51
I would still need to map it from `Expression>` to `Expression>` — Joseph Whitley, Nov 14 '15 at 19:03

Map Dynamic Linq Expression

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