LINQ select in C# dictionary

Question

I have next dictionary in C#

Dictionary<string, object> subDictioanry = new Dictionary<string, object>(); List<Dictionary<string, string>> subList = new List<Dictionary<string, string>>(); subList.Add(new Dictionary<string, string>(){ {"valueLink", "link1"}, {"valueTitle","title1"} }); subList.Add(new Dictionary<string, string>(){ {"valueLink", "link2"}, {"valueTitle","title2"} }); subList.Add(new Dictionary<string, string>(){ {"valueLink", "link3"}, {"valueTitle","title3"} }); subDictioanry.Add("title", "title"); subDictioanry.Add("name", "name"); subDictioanry.Add("fieldname1", subList); Dictionary<string, object> exitDictionary = new Dictionary<string, object>(); exitDictionary.Add("first", subDictioanry); exitDictionary.Add("second", subDictioanry);

Is it possible to get all "valueTitle" with help of LINQ select?

UPDATE: Sorry, i should write it first - i need to get result from exitDictionary, not from subList

This would be way easier to reason about if you used classes instead of dictionaries. Just saying. — millimoose
– millimoose, Commented Nov 1, 2013 at 12:03

Alex Filipovici · Accepted Answer · 2013-11-01 12:28:22Z

If you are searching by the fieldname1 value, try this:

var r = exitDictionary .Select(i => i.Value).Cast<Dictionary<string, object>>() .Where(d => d.ContainsKey("fieldname1")) .Select(d => d["fieldname1"]).Cast<List<Dictionary<string, string>>>() .SelectMany(d1 => d1 .Where(d => d.ContainsKey("valueTitle")) .Select(d => d["valueTitle"]) .Where(v => v != null)).ToList();

If you are looking by the type of the value in the subDictionary (Dictionary<string, object> explicitly), you may do this:

var r = exitDictionary .Select(i => i.Value).Cast<Dictionary<string, object>>() .SelectMany(d=>d.Values) .OfType<List<Dictionary<string, string>>>() .SelectMany(d1 => d1 .Where(d => d.ContainsKey("valueTitle")) .Select(d => d["valueTitle"]) .Where(v => v != null)).ToList();

Both alternatives will return:

title1 title2 title3 title1 title2 title3

Arran · Accepted Answer · 2013-11-01 12:01:47Z

One way would be to first flatten the list with a SelectMany:

subList.SelectMany(m => m).Where(k => k.Key.Equals("valueTitle"));

gleng · Accepted Answer · 2013-11-01 12:05:54Z

3

This will return all the values matching your key valueTitle

subList.SelectMany(m => m).Where(kvp => kvp.Key == "valueTitle").Select(k => k.Value).ToList();

edited Nov 1, 2013 at 12:05

answered Nov 1, 2013 at 11:58

gleng

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1 Comment

Arran Over a year ago

This is incorrect. kvp would not be a KeyValuePair, it would be a Dictionary<string, string>. You are missing a SelectMany to flatten the list.

无名小路 · Accepted Answer · 2021-01-09 14:29:20Z

var res = exitDictionary .Select(p => p.Value).Cast<Dictionary<string, object>>() .SelectMany(d => d) .Where(p => p.Key == "fieldname1") .Select(p => p.Value).Cast<List<Dictionary<string,string>>>() .SelectMany(l => l) .SelectMany(d=> d) .Where(p => p.Key == "valueTitle") .Select(p => p.Value) .ToList();

This also works, and easy to understand.

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