linq Select Collection Column Dynamic

Question

I want select Col1 or Col2 by dynamic in linq command for example

var temp1= "Col1";

thank you for answer

I try by

((ICollection<SanadItem>)x.GetType().GetProperty(temp1).GetType()).Select(g =>...

but get error LINQ to Entities does not recognize the method 'System.Type GetType()' method

public class class1 {
 public int Id {get; set;}
 public string Name {get; set;}
 public string Code {get; set;}
 public ICollection<Class2> Col1 {get; set;}
 public ICollection<Class2> Col2 {get; set;}
}

public class class2 {
 public int Id {get; set;}
 public int Id2 {get; set;}
 public int Bed {get; set;}
 public int Bes {get; set;}
}
...
..
.

public class mycontext:dbcontext{
  public DbSet<Class1> class1 { get; set; }
  public DbSet<Class2> class2 { get; set; }
}

var db = new mycontext()
var qbase = db.class1;
        var qbase2 = qbase.Select(x => new
        {
            Id = x.Id,
            Code = x.Code,
            Name = x.Name,
           //--> I want select x.Col1 or x.Col2 by Dynamic but I cannot use library Linq.Dynamic
            items =  x.Col1.Where(xx => xx.Id2 == x.Id).GroupBy(b=>b.Id2).Select(y =>
                new
                { 
                    Bed = y.Sum(c=>c.Bed),
                    Bes = y.Sum(c => c.Bes),
                })                  
        });

Do you want the whole subselect or just the select part to be dyamic? — user3411327, Apr 25 '14 at 15:29
I want specified column in line items= x.Col1... I want specified Col1 for Col2 in linq — khoshghadam, Apr 25 '14 at 15:44
I mean, do you want the whole expression x.Col1.Where().GroupBy().Select() or just the Select() expression to be dynamic? — user3411327, Apr 25 '14 at 15:51
no all two query is same but Linq Command Where do on Filed Col1 or Col2 — khoshghadam, Apr 25 '14 at 16:24

score 0 · Answer 1 · answered Apr 25 '14 at 07:06

Try it this way

var qbase2 = qbase.Select(x => new
        {
            Id = x.Id,
            Code = x.Code,
            Name = x.Name,
            DynamicCol = (int)s.GetType().GetProperty("Col1").GetValue(x, null) ,
            //Remember to cast the dynamic column according to its datatype
            items =  x.Col1.Where(xx => xx.Id2 == x.Id).GroupBy(b=>b.Id2).Select(y =>
                new
                { 
                    Bed = y.Sum(c=>c.Bed),
                    Bes = y.Sum(c => c.Bes),
                })                  
        });

LINQ to Entities does not recognize the method 'System.Object GetValue(System.Object, System.Object[])' method, and this method cannot be translated into a store expression. — khoshghadam, Apr 25 '14 at 07:20

score 0 · Answer 2 · edited May 23 '17 at 12:14

0

you can not use this x.GetType()... in linq query, because it will not be translated to expression tree, only methods can be used in linq which your provider can translate them to expression tree to run on Data Base side, you can read more about these, from post i added (Here).

and about your question, if you insist on to use reflection, you have to fetch all of your data from data base first, and for this, you need to add .ToList() before your .Select() :

... var qbase2 = qbase.ToList().Select(x => new ...

OR

... var qbase = db.class1.ToList(); ....

edited May 23 '17 at 12:14

Community

1
1

answered Apr 25 '14 at 10:08

Amir Sherafatian

2,083
2
20
32

thank you for answer but I need specified field befor to list because I have very record – khoshghadam Apr 25 '14 at 15:43
you are welcome, but you can never do this in `linq to entities` – Amir Sherafatian Apr 26 '14 at 08:29
thank you amir but this is not linq to entities. this is (Code First) and do in database also other develepor find this problem and use dynamic linq – khoshghadam Apr 26 '14 at 20:45
yes, finally i think, you have no way but dynamic linq – Amir Sherafatian Apr 27 '14 at 04:55

score 0 · Answer 3 · answered Apr 26 '14 at 10:41

I think the following works:

public class DynamicQuery<T>
    {
        public IEnumerable<T> GetByFieldFilterObjectValue(IEnumerable<T> collection, string colName, object value)
        {
            IEnumerable<T> results = collection.Where(d => d.GetType().GetProperty(colName).GetValue(d, null).Equals(value));

            return results;
        }
    }

here is a sample of how I use it - dogs is a collection of Dog:

DynamicQuery<Dog> dogQuery = new DynamicQuery<Dog>();

var dogsSelected = dogQuery.GetByFieldFilterObjectValue(dogs, "Age", 2);

thank you for answer but I want get IQueryable no IEnumerable because Linq do on Database and database have very record — khoshghadam, Apr 26 '14 at 20:48

score 0 · Answer 4 · answered Oct 07 '15 at 21:32

Using answer from Co. Aden and Modifying it. Use AsEnumerable() before select.

var qbase2 = qbase.AsEnumerable().Select(x => new
    {
        Id = x.Id,
        Code = x.Code,
        Name = x.Name,
        DynamicCol = (int)s.GetType().GetProperty("Col1").GetValue(x, null) ,
        //Remember to cast the dynamic column according to its datatype
        items =  x.Col1.Where(xx => xx.Id2 == x.Id).GroupBy(b=>b.Id2).Select(y =>
            new
            { 
                Bed = y.Sum(c=>c.Bed),
                Bes = y.Sum(c => c.Bes),
            })                  
    });

score -1 · Answer 5 · answered Apr 25 '14 at 07:43

-1

Try This one.

var qbase2 = db.class1.select( x => new { x.Id, x.Code,x.Name}).ToList();

answered Apr 25 '14 at 07:43

Harshana Narangoda

775
1
8
23

your command is not dynamic also my query in sample is complex but your code only select 3 column – khoshghadam Apr 25 '14 at 07:46
dynamic means? what do you want to select, in here I select 3 columns.what do you need to do more? – Harshana Narangoda Apr 25 '14 at 07:48
the select may be change var temp = "Family"; select (x=> new {x,id, x.code, temp}).Tolist(); also your select is simple but in top you can see select from collection – khoshghadam Apr 25 '14 at 07:56
Please tell me what do you want to select, then I can help you. – Harshana Narangoda Apr 25 '14 at 08:17

linq Select Collection Column Dynamic

5 Answers5