Chaining / building LINQ query with an OR instead of AND

问题

Edited to be clearer.

If for example I have this IQueryable:

DateTime theDate = new DateTime(2015, 09, 30);

var query = from org in Organisations
            where org.DisableOrganisation == false &&
              org.DisableReports == false
            select new
            {
                OrganisationId = org.OrganisationId
            };

and later in the method I want to add an OR to it, e.g.

// Check to see if the date is the last day of the month.
if (theDate.AddDays(1).Day == 1)
{
    // The following statement introduces an AND but I want to make this an OR.
    query = query.Where(x => x.Frequency == "M");
}

This effectively makes my query...

var query = from org in Organisations
            where org.DisableOrganisation == false &&
              org.DisableReports == false &&
              org.Frequency == "M"
            select new
            {
                OrganisationId = org.OrganisationId
            };

but I want to make it...

var query = from org in Organisations
            where (org.DisableOrganisation == false &&
              org.DisableReports == false) ||
              org.Frequency == "M"
            select new
            {
                OrganisationId = org.OrganisationId
            };

How do I go about making this an OR instead of an AND ?

P.S. Cannot use PredicateBuilder as it is essentially LinqKit which has a dependency of EntityFramework (≥ 6.0.2), I'm stuck using EF 4.3.1

SOLVED: Thanks to D Stanley (To be honest I had used this form of solution before, I simply forgot about it).

DateTime theDate = new DateTime(2015, 09, 30);
bool isEndOfMonth = theDate.AddDays(1).Day == 1;

var query = from org in Organisations
            where (org.DisableOrganisation == false &&
              org.DisableReports == false) ||
              (isEndOfMonth &&
               pr.ProfileType == "L" && 
               pr.Frequency == "M")
            select new
            {
                OrganisationId = org.OrganisationId
            };

回答1:

You can't do it by chaining - you'll have to use some sort of expression builder, or just build that in your original filter:

var day = theDate.AddDays(1).Day;

var query = from org in Organisations
            where (org.DisableOrganisation == false &&
                   org.DisableReports == false) ||
                  (day == 1 &&
                   org.ProfileType == "L" && 
                   org.Frequency == "M")
            select new
            {
                OrganisationId = org.OrganisationId
            };

回答2:

To combine conditions with OR instead of AND, use the PredicateBuilder:

predicate = predicate.Or(p => p.Description.Contains (temp));
return dataContext.Products.Where(predicate);

来源：https://stackoverflow.com/questions/32866123/chaining-building-linq-query-with-an-or-instead-of-and