Lambda Expresssion - using EntityFramework Include() and Any operation?

Question

The following code is working

var queryResults = _db.Projects
           .Include("Participants.Person")
           .Where(Project => Project.Participants.Any(Parti => Parti.Person.FirstName == "test3"));

I am dynamically building lambda expression. In order to achieve the above I have to write lots of code.

I would like to achieve the following.

var queryResults = _db.Projects
           .Include("Participants.Person")
           .Where(Project => Project.Participants.Person.FirstName == "test3"));

Any suggestion please share.

Edited section following

I am trying with Any operation. But i m getting exception in this line. Any suggestions?

MemberExpression propertyOuter = Expression.Property(c, "Participant");

ParameterExpression tpe = Expression.Parameter(typeof(Participant), "Participant");
Expression left1 = Expression.Property(tpe, typeof(Participant).GetProperty("Person"));
Expression left2 = Expression.Property(left1, typeof(Person).GetProperty("FirstName"));
Expression right1 = Expression.Constant(filter.FieldValue);
Expression InnerLambda = Expression.Equal(left2, right1);
Expression<Func<Participant, bool>> innerFunction = Expression.Lambda<Func<Participant, bool>>(InnerLambda, tpe);

MethodInfo method = typeof(Enumerable).GetMethods().Where(m => m.Name == "Any" && m.GetParameters().Length == 2).Single().MakeGenericMethod(typeof(Participant));

MemberExpression propertyOuter = Expression.Property(c, "Participant");

var anyExpression = Expression.Call(method, propertyOuter, innerFunction);

Yann Olaf · Answer 1 · 2012-11-02T14:23:00.753

0

Perhaps this is working for you.

var queryResults = _db.Persons
   .Where( p => p.FirstName == "test3")
   .SelectMany(p => p.Participant.Projects)
   .Include("Participants.Person");

Edit: or if person has many participants

var queryResults = _db.Persons
   .Where( p => p.FirstName == "test3")
   .SelectMany(p => p.Participants.SelectMany(par => par.Projects))
   .Include("Participants.Person");

edited Nov 02 '12 at 14:23

answered Nov 02 '12 at 13:51

Yann Olaf

597
3
12

No, I am not finding sub entities this line .SelectMany(p => p.Participants.) – sivaL Nov 02 '12 at 14:06
have you selected from _db.Persons as suggested or form _db.Projects? – Yann Olaf Nov 02 '12 at 14:09
I selected from _db.Persons only. – sivaL Nov 02 '12 at 14:15
Ok this means person and participant is in a M to N relation, right? – Yann Olaf Nov 02 '12 at 14:19
see edited suggestion. ...SelectMany(p => p.Participants.SelectMany(par => par.Projects))... – Yann Olaf Nov 02 '12 at 14:34

score 0 · Accepted Answer · edited May 23 '17 at 11:48

I got the solution, its working.

Lambda expression

var queryResults = _db.Projects
       .Include("Participants.Person")
       .Where(Project => Project.Participants.Any(Participant => Participant.Person.FirstName == "test3"));

Source code to build dynamic lambda expression

 ParameterExpression c = Expression.Parameter(typeof(T), entityType.Name);
 ParameterExpression tpe = Expression.Parameter(typeof(Participant), "Participant");
 Expression left1 = Expression.Property(tpe, typeof(Participant).GetProperty("Person"));
 Expression left2 = Expression.Property(left1, typeof(Person).GetProperty("FirstName"));
 Expression right1 = Expression.Constant(filter.FieldValue);
 Expression InnerLambda = Expression.Equal(left2, right1);
 Expression<Func<Participant, bool>> innerFunction = Expression.Lambda<Func<Participant, bool>>(InnerLambda, tpe);

 MethodInfo method = typeof(Enumerable).GetMethods().Where(m => m.Name == "Any" && m.GetParameters().Length == 2).Single().MakeGenericMethod(typeof(Participant));

 var outer = Expression.Property(c, typeof(Project).GetProperty("Participants"));

 var anyExpression = Expression.Call(method, outer, innerFunction);

This helped lot. Building a dynamic expression tree to filter on a collection property

Lambda Expresssion - using EntityFramework Include() and Any operation?

2 Answers2