CODEWITHSUNDEEP
c#entity-frameworklinqiqueryablelinqkit
Ruslan Borovok
Ruslan Borovok

Reputation: 530

How to select a value in LINQ Query in depends on Expression result?

I'm using EF6 and I'm looking for a solution to build a query that should select one of the fields in depends on a value that Expression returns. I'm playing with the LINQKit library for that but get a failure with this.

So I've created the reusable predicate that calculates logic in DB:

public partial class Study
{
    public static Expression<Func<Study, bool>> ShouldNameBeDisplayedForStaffExpression(int staffId)
    {
        return study =>
            (study.StudyViewAccessId == 1 && study.StudyEditAccessId == 1)
            || study.Roles.Any(y => y.StaffId == staffId);
        //Here other additional logic
    }
}

And now I need to set up proper value to Name field depends on the result that the predicate returns. The main requirement - it should be done on the query level (in IQueryable collection). The studiesCoreModelsQuery is EF6 EntitySets.

IQueryable<Study> studiesCoreModelsQuery = this._dbContext.Studies;
IQueryable<StudyViewModel> query = studiesCoreModelsQuery.AsExpandable().Select(x => new StudyViewModel
{
    Name = Study.ShouldNameBeDisplayedForStaffExpression(staffId).Invoke(x)
        ? x.Name
        : "Hidden"
});

Cannot understand how to get a result of Expression execution in Select. I will be appreciated for any help.

Upvotes: 0

Views: 292

Answers (1)

Ruslan Borovok
Ruslan Borovok

Reputation: 530

@Ivan Stoev you are right.Your suggestion solved the issue. Work code next:

IQueryable<Study> studiesCoreModelsQuery = this._dbContext.Studies;
var expression = Study.ShouldNameBeDisplayedForStaffExpression(staffId);
IQueryable<StudyViewModel> query = studiesCoreModelsQuery.AsExpandable().Select(x => new StudyViewModel
{
    Name = expression.Invoke(x)
        ? x.Name
        : "Hidden"
});

Upvotes: 1

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