C#•2y ago

How to convert a Predicate to Expression

Hi friends, I have the method bellow My Question is is there any way or technique to Convert that Predicate to an Expression because the method should return an Expression ???

5 Replies

M B V R K•2y ago

Method:

    public Expression<Func<Core.Entities.StudentAbsence , bool>> GetPredicate( 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 ) );

        var whereAbsenceDateContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.AbsenceDate.ToFrenchDateString().Contains( query.Value ) );

        var whereAbsenceTimeContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.AbsenceTime.ToTimeString().Contains( query.Value ) );

        var whereCombinedDataAndTimeContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => ( x.AbsenceDate.ToFrenchDateString() + " " + x.AbsenceTime.ToTimeString() ).Contains( query.Value ) );

        var whereStudentIdEqualsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.StudentEnrollment.StudentId.ToString().Contains( query.Value ) );

        var whereBranchEqualsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.StudentEnrollment.Group.BranchId == query.Value );

        var whereGroupEqualsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.StudentEnrollment.GroupId.ToString() ==  query.Value );

    public Expression<Func<Core.Entities.StudentAbsence , bool>> GetPredicate( 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 ) );

        var whereAbsenceDateContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.AbsenceDate.ToFrenchDateString().Contains( query.Value ) );

        var whereAbsenceTimeContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.AbsenceTime.ToTimeString().Contains( query.Value ) );

        var whereCombinedDataAndTimeContainsValue = new Predicate<Core.Entities.StudentAbsence>( x => ( x.AbsenceDate.ToFrenchDateString() + " " + x.AbsenceTime.ToTimeString() ).Contains( query.Value ) );

        var whereStudentIdEqualsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.StudentEnrollment.StudentId.ToString().Contains( query.Value ) );

        var whereBranchEqualsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.StudentEnrollment.Group.BranchId == query.Value );

        var whereGroupEqualsValue = new Predicate<Core.Entities.StudentAbsence>( x => x.StudentEnrollment.GroupId.ToString() ==  query.Value );

// Combine the predicates into a single
var predicate = new Predicate<Core.Entities.StudentAbsence>( x => 
whereFullNameContainsValue( x )            ||
whereSchoolSubjectTitleContainsValue( x )  ||
whereAbsenceDateContainsValue( x )         ||
whereAbsenceTimeContainsValue( x )         ||
whereCombinedDataAndTimeContainsValue( x ) ||
whereStudentIdEqualsValue( x )             ||
whereBranchEqualsValue( x )                ||
whereGroupEqualsValue( x )                 ||

( whereGroupEqualsValue( x ) && whereAbsenceDateContainsValue( x ) ) );

        // Convert the predicate to an expression
        var expression = // Idon't kknow how to do it

        return expression;
    }

// Combine the predicates into a single
var predicate = new Predicate<Core.Entities.StudentAbsence>( x => 
whereFullNameContainsValue( x )            ||
whereSchoolSubjectTitleContainsValue( x )  ||
whereAbsenceDateContainsValue( x )         ||
whereAbsenceTimeContainsValue( x )         ||
whereCombinedDataAndTimeContainsValue( x ) ||
whereStudentIdEqualsValue( x )             ||
whereBranchEqualsValue( x )                ||
whereGroupEqualsValue( x )                 ||

( whereGroupEqualsValue( x ) && whereAbsenceDateContainsValue( x ) ) );

        // Convert the predicate to an expression
        var expression = // Idon't kknow how to do it

        return expression;
    }

I hope someone here to suggest a solution and massive thanks in advance

dancepanda42•2y ago

Expression<Func<Core.Entities.StudentAbsence, bool>> expression = (input) => predicate(input);

Expression<Func<Core.Entities.StudentAbsence, bool>> expression = (input) => predicate(input);

i think this should work

reflectronic•2y ago

you can’t “convert” a predicate to an expression, except perhaps as an expression that invokes that predicate if you want the full expression tree you need to create it directly from the lambda

M B V R K•2y ago

This one works perfectly Thanks you a lot mate

Accord•2y ago

Ask the thread owner or member with permission to close this!

Gaming

Programming

How to convert a Predicate to Expression