CODEWITHSUNDEEP
c#.netlinqlistlinq-group
M Afifi
M Afifi

Reputation: 4795

LINQ Dictionary Non-Distinct Values

I am struggeling a little with trying to write the LINQ query to do the following,

public class MyClass
{
    public int ID {get; set;}
    public int Name {get; set;}
    public IEnumerable<string> SomeIEnumerable {get; set;}
}

I am trying to create the object using LINQ from a DB query that would return something as follows,

ID    Name     SomeString
0     NameA    "MyValue"
1     NameB    "Value1"
1     NameB    "Value2"
2     NameC    "Value"

The LINQ is pretty easy to write as well,

from DataRow row in dataSet.Tables[0].Rows
select new MyClass
{
    ID = (int)row["ID"],
    Name = row["Name"].ToString(),
    SomeIEnumerable = new List<string>{ row["SomeString"].ToString() }
};

The tricky part is how do I turn this into a Dictionary where dictionary[1].SomeIEnumerable = {"Value1", "Value2"}

A simple ToDictionary would throw an ArgumentException

The main issue here, is how do I handle the fact that the keyis not distinct, and be able to lookup in the temporary dictionary the existing value to add to it the values I am interested in.

Upvotes: 1

Views: 1629

Answers (3)

leppie
leppie

Reputation: 117220

Instead of calling ToDictionary, call ToLookup. :)

Upvotes: 3

M Afifi
M Afifi

Reputation: 4795

Answer thanks to @Tilak is,

from DataRow row in dataSet.Tables[0].Rows
group row by new
{
    ID = (int) row["ID"],
    Name = row["Name].ToString()
} into rowGroup
select new MyClass
{
    ID = rowGroup.Key.ID,
    Name = rowGroup.Key.Name,
    SomeIEnumerable =
        from row in rowGroup
        select row["SomeString"].ToString()
};

Upvotes: 1

Tilak
Tilak

Reputation: 30698

You can also your grouping, and then use IGrouping to retrieve the list of items in the group

Sample code

    var simulatedData = Enumerable.Range(0,10).Select(x=> new {Key=x%3+1, Index=x}); 
    var dict = simulatedData.GroupBy(x=>x.Key).ToDictionary(x=>x.Key, x=>x.Select(t=>t.Index));

Upvotes: 3

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