Linq Expression to Turn DataTable to Dictionary of <Key, List<Values>>

Question

I am trying to convert a DataTable of the form

Key  Value
1    A
1    B
1    C
2    X
2    Y

To a Dictionary

1 [A,B,C]
2 [X,Y]

The lambda expression I am using is

GetTable("..sql..").AsEnumerable().
    .Select(r => new {Key = r.Field<int>("Key"), Val = r.Field<string>("Value")})
    .GroupBy(g => g.Key)
    .ToDictionary(a => a.Key, a => String.Join(",", a.Value))

But it fails with "Cannot convert lambda expression to type 'System.Collections.Generic.IEqualityComparer' because it is not a delegate type"

How can I accomplish this?

Answer 1

This does it:

GetTable("..sql..").AsEnumerable().
    .Select(r => new {Key = r.Field<int>("Key"), Val = r.Field<string>("Value")})
    .GroupBy(g => g.Key)
    .ToDictionary(a => a.Key, a => String.Join(",", a.Select(x => x.Value).ToList()))

Answer 2

Here's another way you can do it...

GetTable("..sql..").AsEnumerable()
    .GroupBy(x => x.Field<int>("Key"))
    .ToDictionary(grp => grp.Key, x => x.Select(y => y.Field<string>("Value")).ToList());