Datatable todictionary several columns

Question

I'm trying to convert a datatable to a dictionary using the method described here, but I get an error

Cannot implicitly convert type System.Collections.Generic.Dictionary>' to 'System.Collections.Generic.Dictionary``.

This link helped, but only one value is pulled into the dictionary, not several which is what I need.

Thanks for any help.

public class MCEAV
{
    public int ID { get; set; }
    public int BOOK_ID { get; set; }
    public double DATA { get; set; }
}

Dictionary<int, MCEAV> dctGREEKS = new Dictionary<int, MCEAV>();
dctGREEKS = DATActx.MONTECARLO_EAVs.Select(Z => new { Z.ID, Z.BOOK_ID, Z.DATA}).ToDictionary(Z => Z.ID);

If you have 1 value in `MONTECARLO_EAVs` you'll get one values in the dictionary. That is simple. — Zein Makki, Jul 29 '16 at 06:51

score 2 · Accepted Answer · answered Jul 29 '16 at 06:44

You need to specify the name of the class when using new else it is an anonymous type:

dctGREEKS = DATActx.MONTECARLO_EAVs.Select(Z => 
                               new MCEAV()
                               { 
                                  ID = Z.ID, 
                                  BOOK_ID = Z.BOOK_ID, 
                                  DATA = Z.DATA
                               }).ToDictionary(Z => Z.ID);

So new { Z.ID, Z.BOOK_ID, Z.DATA} is an instance of an anonymous type created by the compiler while new MCEAV() is an instance of type MCEAV which is what you want for your dictionary.

Thankyou! this was driving me crazy, I had run ways to get the code to work. — Zeus, Jul 29 '16 at 06:52

score 2 · Answer 2 · answered Jul 29 '16 at 06:54

Based on your code, I guess you want something like this.

var result = dt.AsEnumerable()
        .ToDictionary(x=>x.Field<int>("ID"), 
                      x=> new MCEAV() 
                      {
                          ID = x.Field<int>("ID"),
                          BOOK_ID = x.Field<int>("BOOK_ID"), 
                          DATA = x.Field<double>("DATA") 

                      });

Check this Example

Datatable todictionary several columns

2 Answers2