CODEWITHSUNDEEP
c#linqlinq-to-sql
ethem
ethem

Reputation: 2908

LINQ Method Syntax - how to accomplish dynamic Linq statements

I use Linq to Entities to retrieve my records from DB. The function below is in a method. Method has some parameters (arguments) like group, datefrom, dateto, place, state , searchtext etc. etc.

the whole idea is if these parameters are not empty or null then accomplish the LINQ statments. The way I'm doing is I'm checking whether there is a value or not. if it has the value then I pass e.g. a.no_group= group if it doesn't has a value then I pass a statement like a.id!=-1, which is always true.

Problem: I mean I'm not happy with passing in every statement like "a.id != -1" which is always true . I use this because I have to put a value there. But I'm not happy with this way of doing it... (it works!)

Question: The question is: this right way of doing? 1- Can I replace a.id != -1 with something else ?

2- If you see the whole linq statement is duplicated because of language check. As you see the last linq statement checks on language 'Dutch' or 'French'... How to avoid dupliation?

3- I'm checking whether the current date (datetime.now) is between date_begin and date_end. Is this correct way...

The whole code works fine, but I think I'm complicating the code which can be much simpler...

But how?

if (Language == ConfBouwHelper.LanguageEnum.French)
{
//FRENCH RECORDS
 listAgendaItems = dc.agenda.Where(a =>
   ((String.IsNullOrEmpty(group)) ? (a.id != -1) : (a.no_group == group))
&& ((activityType.Equals("ALL")) ? (a.id != -1) : (a.type_manifestation == activityType))
&& ((String.IsNullOrEmpty(dateFrom)) ? (a.id != -1) : (a.date_debut.Value >= dateFrom))
&& ((String.IsNullOrEmpty(dateTo)) ? (a.id != -1) : (a.date_debut.Value <= dateTo))
&& ((String.IsNullOrEmpty(place)) ? (a.id != -1) : (a.emplacement.Contains(place)))
&& ((String.IsNullOrEmpty(state)) ? (a.id != -1) : (a.cd_prov == state))
&& ((String.IsNullOrEmpty(searchText)) ? (a.id != -1) : (a.libelle_activite.Contains(searchText)))
&& ((a.date_begin_display.HasValue ? DateTime.Now >= a.date_begin_display.Value : a.id != -1) &&
   (a.date_end_display.HasValue ? DateTime.Now <= a.date_end_display.Value : a.id != -1))
&& (a.langue == "FRENCH" || a.langue == "B")).ToList<agenda>(); //GET FRENCH
}
else
//DUTCH RECORDS
{
 listAgendaItems = dc.agenda.Where(a =>
   ((String.IsNullOrEmpty(group)) ? (a.id != -1) : (a.no_group == group))
&& ((activityType.Equals("ALL")) ? (a.id != -1) : (a.type_manifestation == activityType))
&& ((String.IsNullOrEmpty(dateFrom)) ? (a.id != -1) : (a.date_debut.Value >= dateFrom))
&& ((String.IsNullOrEmpty(dateTo)) ? (a.id != -1) : (a.date_debut.Value <= dateTo))
&& ((String.IsNullOrEmpty(place)) ? (a.id != -1) : (a.emplacement.Contains(place)))
&& ((String.IsNullOrEmpty(state)) ? (a.id != -1) : (a.cd_prov == state))
&& ((String.IsNullOrEmpty(searchText)) ? (a.id != -1) : (a.libelle_activite.Contains(searchText)))
&& ((a.date_begin_display.HasValue ? DateTime.Now >= a.date_begin_display.Value : a.id != -1) &&
   (a.date_end_display.HasValue ? DateTime.Now <= a.date_end_display.Value : a.id != -1))

&& (a.langue == "DUTCH" || a.langue == "B")).ToList<agenda>(); //GET DUTCH
}

Upvotes: 2

Views: 466

Answers (1)

Daniel Hilgarth
Daniel Hilgarth

Reputation: 174299

You can add multiple where clauses:

var query = dc.agenda;
if(!String.IsNullOrEmpty(group))
    query = query.Where(a => a.no_group == group)
if(!activityType.Equals("ALL"))
    query = query.Where(a => a.type_manifestation == activityType)
// and so on for all your conditions...

if (Language == ConfBouwHelper.LanguageEnum.French)
    query = query.Where(a => (a.langue == "FRENCH" || a.langue == "B"));
else
    query = query.Where(a => (a.langue == "DUTCH" || a.langue == "B"));

listAgendaItems = query.ToList<agenda>();

This is a lot cleaner and readable and also solves the problem with the duplication because of the languages.

Upvotes: 2

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