C
C#•3y ago
M B V R K

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
M B V R KOP•3y 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
dancepanda42•3y 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
reflectronic•3y 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
M B V R KOP•3y ago
This one works perfectly Thanks you a lot mate
Accord
Accord•3y ago
Ask the thread owner or member with permission to close this!

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