Using a Lambda Expression Over a Dictionary<string, List<object>> in C#

Question

I have a dictionary that looks like this:

public Dictionary<string, List<EquipmentRow>> TableRows { get; set; }

EquipmentRow class:

public class EquipmentRow
{
    public string Model { get; set; }
    public bool New { get; set; }
}

I want to create/filter a structurally same Dictionary as the previous one which only contains a list of items in which property New is equal to true. How to achieve that by using a Lambda Expression? For example:

var newLocationDevices = locationDevices.Where(x => x.Value.Where()) etc.

mehrandvd · Accepted Answer · 2022-06-07 17:17:44Z

2

You can do it simply using this code:

var newLocationDevices = locationDevices
    .ToDictionary(
        o => o.Key,
        o => o.Value.Where(i => i.New).ToList()
    );

edited Jun 7, 2022 at 17:17

answered Jun 7, 2022 at 17:13

mehrandvd

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5 Comments

Domagoj Hamzic Over a year ago

'KeyValuePair<string, List<EquipmentRow>>' does not contain a definition for 'New'

mehrandvd Over a year ago

@DomagojHamzic I had a typo which I've just fixed it. i=>i.New instead of 'o.New'

Prasad Telkikar Over a year ago

Will it filter Key value elements where New = false;?

mehrandvd Over a year ago

@PrasadTelkikar As I understood the problem, only the inner list is needed to be filtered, not the outer one. Otherwise, another Where is needed just as you've mentioned.

Prasad Telkikar Over a year ago

What if inner list contains single element and it is New=false

Prasad Telkikar · Accepted Answer · 2022-06-07 17:06:22Z

1

You can filter dictionary using .Where() clause and check bool value using .Any(),

var result = locationDevices
      .Where(x => x.Value.Any(x => x.New)) //Filter existing dictionary
      .ToDictionary(x => x.Key, x => x.Value.Where(y => y.New).ToList()); //Create new Dictionary.

answered Jun 7, 2022 at 17:06

Prasad Telkikar

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3 Comments

Domagoj Hamzic Over a year ago

thanks, also correct answer but I can not mark >1 answer as correct :(

Peter Smith Over a year ago

@DomagojHamzic But you can do a +1

ScottyD0nt Over a year ago

this is slightly different the accepted answer, keys that would have an empty list are not going to be present in the dictionary in this version.

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