C
C#•3y ago
M B V R K

How to return a named predicates

Hi friends, I want to build a Method that returns a set of Predicates Example: 
    private Predicate<Core.Entities.StudentAbsence>[] GetPredicates( SearchStudentAbsencesQuery query )
    {
        var whereFullNameContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => ( x.StudentEnrollment.Student.FirstName + x.StudentEnrollment.Student.FamilyName ).Contains( query.Value ) );
        var whereSchoolSubjectTitleContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.SchoolSubject.FullTitle.Contains( query.Value ) );
// Other predicates

        var predicates = new[]
                         {
                             whereFullNameContainsValue ,
                             whereSchoolSubjectTitleContainsValue ,
                             // Others
                         };
        
        return predicates;
    }
    private Predicate<Core.Entities.StudentAbsence>[] GetPredicates( SearchStudentAbsencesQuery query )
    {
        var whereFullNameContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => ( x.StudentEnrollment.Student.FirstName + x.StudentEnrollment.Student.FamilyName ).Contains( query.Value ) );
        var whereSchoolSubjectTitleContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.SchoolSubject.FullTitle.Contains( query.Value ) );
// Other predicates

        var predicates = new[]
                         {
                             whereFullNameContainsValue ,
                             whereSchoolSubjectTitleContainsValue ,
                             // Others
                         };
        
        return predicates;
    }
The Issue: How do I can return those predicates but everyone with a name like properties, let me explain more depending on the example I provided the use of that result will be like this: 
var predicates = GetPredicates(Query);

var result = await db.<StudentAbsence>().Where( predicates[0] || predicates[1] //... ).ToListAsync()
var predicates = GetPredicates(Query);

var result = await db.<StudentAbsence>().Where( predicates[0] || predicates[1] //... ).ToListAsync()
as you will notice that to get every predicate I should use its index, instead of that I want when I got the predicates use their names like this following 
var predicates = GetPredicates(Query);

var result = await db.<StudentAbsence>().Where( predicates.whereFullNameContainsValue  || predicates.whereSchoolSubjectTitleContainsValue //... ).ToListAsync()
var predicates = GetPredicates(Query);

var result = await db.<StudentAbsence>().Where( predicates.whereFullNameContainsValue  || predicates.whereSchoolSubjectTitleContainsValue //... ).ToListAsync()
I hope the explanation of the issue is clear, please is this even possible, if yes how do I can achieve this ? and massive thanks.
8 Replies
becquerel
becquerel•3y ago
you will want to make a class that contains properties with your desired names that provides access to these predicates or return a named tuple, but that's yucky
M B V R K
M B V R KOP•3y ago
hmmm, the problem is this method will works generically and the names of predicates will not be fixed
becquerel
becquerel•3y ago
then I think you're out of luck if you want to use names at compile time, you have to know the names at compile time
M B V R K
M B V R KOP•3y ago
hmmmm so this maybe impossible right ?
becquerel
becquerel•3y ago
unless i'm missing something, and you don't wanna make a new class, then yeah i think so
M B V R K
M B V R KOP•3y ago
Hmm this be done using Anonymous types ?
becquerel
becquerel•3y ago
possibly i don't mess around with those too much
phaseshift
phaseshift•3y ago
Make a class with normal properties (as already said), or return a dict and use string or enum as the key

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