I am trying to create a dictionary that can hold multiple values per key, and I have created an class called Pair that consists of two strings. I have defined idDictionary to contain a string as the key, and Pair as the value, but I am unsure how to write the ToDictionary statement as this concept is new to me, and I couldn't find any examples of this.
Dictionary<string, Pair<string, string>> idDictionary = new Dictionary<string, Pair<string, string>>();
I know with a regular generic Dictionary of I would simply use something like this:
idDictionary = resultData.Rows.Select(row => row.Split(','))
.ToDictionary(id => id[0], id => id[1]);
I am not sure how I would implement something similar for the object called Pair. Maybe I'm missing something really simple, but many thanks to those with answers.
EDIT to include full code block and more thorough explanation
The original code block is here (with a generic dictionary). The reason I am changing this is due to the fact that if there is more than 1 value per key, the application errors out due to duplicate keys.
private List<ImportItem<T>> ProcessReportResult(CSVTable resultData, ICollection<ImportItem<T>> data, Func<T, string> keyFilter)
{
WriteLog("{1}{0} records found.{1}", resultData.Rows.Length, Environment.NewLine);
//key = Order Number; value = Order ID
var idDictionary = resultData.Rows.Select((row => row.Split(','))).ToDictionary(id => id[0], id => id[1]);
idDictionary.ForEach(id => WriteLog("Input Id = {0} - Matching record Id = {1}", id.Key, id.Value));
var processList = data.Where(item => idDictionary.ContainsKey(keyFilter(item.DataItem))).ToList();
processList.ForEach(item => item.id = idDictionary[keyFilter(item.DataItem)]);
return processList;
}
A genral solution to get the one to many key value store can be achieved via grouping but that would require to have value as List of items. If I try to explain it via your given sample then the query to convert the rows to per key multi value store can be created by:
idDictionary =
resultData.Rows
.GroupBy(row => row.Id, row => row.Split(','))
.ToDictionary(g => g.Key, g => g.ToList());
Update:
Specific solution to your problem. Assuming that data would have structure something like:
List<Row> rows = new List<Row>{
new Row{
values = "1,A"
},
new Row{
values = "2,C,D,E"
},
new DataRow{
values = "3,E,X,CV,B"
},
};
You can use the Group here as well to get the Key, Value(List). Note, Here I have skipped the first value which is already captured as key at index 0.
var idDictionary =
rows.GroupBy(row => row.values.Split(',')[0],
row => row.values.Split(',').Skip(1))
.ToDictionary(g => g.Key, g => g.ToList());
This will give you the result like:
/* output -
|1, (A)|
|2, (C,D,E)|
|3, (E,X,CV,B)|
*/
Though you have to change the implementation for fetching the values via List.
But this solution will prevent the Program if there are more than one values found per key.
Not sure exactly what you need maybe this simple example will help?
idDictionary = resultData.Rows
.Select((row => row.Split(',')))
.ToDictionary<string, Pair<string, string>>
(id => id[0],id => new Pair(id[1],id[1]));
This version of ToDictionary takes two functions, one that returns the key and one that returns the value for each item in the enumeration.
You'll have to decide whether you want a tuple-based approach (or pair even) if you know how many items are in each row or if you need to consider that each row may have a different number of items.
// Setup sample data
var resultData = new
{
Rows = new string[] { "1,A,B,C", "2,A,B", "3,A,B,C,D" }
};
// If same length for each row, tuple would work easily
// Dictionary<string, Tuple<string, string>>
var tuples = resultData.Rows
.Select(r => r.Split(','))
.ToDictionary(
r => r[0],
r => Tuple.Create(r[1], r[2])
);
// If length is variable, then some type of collection could be better
// Dictionary<string, List<string>>
var lists = resultData.Rows
.Select(r => r.Split(','))
.ToDictionary(
r => r[0],
r => r.Skip(1).ToList() // Skip adding id element
);
Here is the output for the 1st item to compare each:
?lists["1"]
Count = 3
[0]: "A"
[1]: "B"
[2]: "C"
?tuples["1"]
{(A, B)}
Item1: "A"
Item2: "B"
The original code block is here (with a generic dictionary). The reason I am changing this is due to the fact that if there is more than 1 value per key, the application errors out due to duplicate keys.
Seems like what you are looking for is ToLookup
"Lookup<TKey, TElement>
represents a collection of keys each mapped to one or more values."
.
var idDictionary = resultData.Rows.Select((row => row.Split(',')))
.ToLookup(id => id[0], id => id[1]);
EDIT
A short sample:
var lines = new string[] { "a,b", "a,c", "d,e" };
var dict = lines.Select(line => line.Split(','))
.ToLookup(x => x[0], x => x[1]);
result:
Key: a Value: [b,c]
Key: e Value: [e]
Sample usage:
Console.WriteLine(string.Join(",", dict["a"]));
Related
Looking for someone to help me with C#, LINQ.
I have a Dictionary<int,int> that I am ordering like so: .OrderBy(_ => _.Value).ThenBy(_ => ThisMethodReturnsAnotherIReadOnlyDict<int,int>()).ThenByDescending(_ => _.Key).
What I want is to order the first dictionary by its value and then if there are still equal values I want that tie to be broke by the ThisMethodReturnsAnotherIReadOnlyDict<int,int>(). This first key/value of this ThisMethodReturnsAnotherIReadOnlyDict to break the tie and be on top. And finally, if everything fails, then order by it's key descending.
Some data for this like:
(First Dictionary)
[1,400]
[2,550]
[3,200]
[4,200]
(Second dictionary)
[3,50]
[4,140]
[2,600]
[1,700]
For this scenario I want my ordering to return: [3,50]
Can anyone help please?
Thanks!
It looks like you're looking for something like this:
var firstDict = new Dictionary<int, int>() {
{1,400},
{2,550},
{3,200},
{4,200}
};
var secondDict = new Dictionary<int, int>() {
{3,50},
{4,140},
{2,600},
{1,700}
};
var result = (from kvp in firstDict
join tieBreaker in secondDict on kvp.Key equals tieBreaker.Key
select new { kvp.Key, V1 = kvp.Value, V2 = tieBreaker.Value })
.OrderBy(x => x.V1)
.ThenBy(x => x.V2)
.ThenByDescending(x => x.Key)
.First();
This will join the first and second dictionaries together by its keys and will, respectively, order by the value of the first dictionary, the value of the second dictionary and then descending by the key itself.
How about:
var ans = firstDict
.OrderBy(kv => kv.Value)
.ThenBy(kv => ThisMethodReturnsAnotherIReadOnlyDict<int,int>().TryGetValue(kv.Key, out var val2) ? val2 : kv.Key)
.ToList();
Unless ThisMethodReturnsAnotherIReadOnlyDict<int,int> may change, you may want to cache the return value in a variable before sorting.
I have a List<KeyValuePair<string, List<string>>, so the data looks something like:
user1, [trigger1,trigger2,trigger3]
user2, [trigger1,trigger4]
user3, [trigger2,trigger3,trigger4]
user1, [trigger0,trigger4]
I would like to make this a Dictionary<string,List<string>>, but directly this fails because there would be duplicate keys. Is there a way to merge the contents of the attached Values on the fly (meaning if there is user1 twice as keys, combine the two associated Lists<>) in LINQ?
You need to group KVPs on Key, and use SelectMany to "flatten" the lists. If you do not want duplicates, use Distinct() to remove them:
var res = list
.GroupBy(p => p.Key)
.ToDictionary(
g => g.Key
, g => g.SelectMany(p => p.Value).Distinct().ToList()
); // ^^^^^^^^^^
// Remove Distinct() if you would like to keep all items
A GroupBy will do most of the work, combined with making a list of all the grouped items and you are done. The result of the GroupBy contains an enumerable of lists, so we have to select all string items using SelectMany and construct a list out of that.
Dictionary<string, List<string>> d = l.GroupBy(k => k.Key)
.ToDictionary( k => k.Key
, k => k.SelectMany(s => s.Value).ToList()
);
You can accomplish this through a series of chained LINQ queries in the following order :
GroupBy() - This will create groups of each of your individual users to avoid issues when creating your dictionary (namely duplicate keys).
ToDictionary() - This method will work to bind a given set of data using a key and a value, since you already have your keys (via the earlier call), you just need to get your values from each group.
SelectMany() - This will select all of the individual values from your earlier groups, essentially merging all of the items from each set of users into a single collection.
Distinct() - This will be applied on the list of strings generated in the previous step to remove any duplicates. If you want to allow duplicates, simply remove this step.
Implementing this would look something like the following snippet of code :
// Group the collections by user and then select the keys based on those users
var dictionary = list.GroupBy(l => l.Key)
.ToDictionary(
x => x.Key,
x => x.SelectMany(l => l.Value)
.Distinct()
.ToList()
);
Example
// Example of your existing data
var list = new List<KeyValuePair<string, List<string>>>(){
new KeyValuePair<string,List<string>>("User 1", new List<string>(){ "trigger1" ,"trigger2", "trigger3" }),
new KeyValuePair<string,List<string>>("User 2", new List<string>(){ "trigger1" ,"trigger2" }),
new KeyValuePair<string,List<string>>("User 3", new List<string>(){ "trigger2" ,"trigger3", "trigger4" }),
new KeyValuePair<string,List<string>>("User 1", new List<string>(){ "trigger0" ,"trigger4" }),
};
// Group the collections by user and then select the keys based on those users
var dictionary = list.GroupBy(l => l.Key)
.ToDictionary(
x => x.Key,
x => x.SelectMany(l => l.Value)
.Distinct()
.ToList()
);
// Output each key with it's associated values
foreach(var key in dictionary.Keys)
{
Console.WriteLine("Key: " + key + ", Values: " + String.Join(",",dictionary[key].ToArray()));
}
// Example output
// Key: User 1, Values: trigger1,trigger2,trigger3,trigger0,trigger4
// Key: User 2, Values: trigger1,trigger2
// Key: User 3, Values: trigger2,trigger3,trigger4
You can see an interactive version of this here.
Try this :
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
List<KeyValuePair<string, List<string>>> myList = new List<KeyValuePair<string,List<string>>>() {
new KeyValuePair<string, List<string>>("user1", new List<string> { "trigger1","trigger2","trigger3"}),
new KeyValuePair<string, List<string>>("user2", new List<string> { "trigger1","trigger4"}),
new KeyValuePair<string, List<string>>("user3", new List<string> { "trigger2","trigger3","trigger4"}),
new KeyValuePair<string, List<string>>("user1", new List<string> { "trigger0","trigger4"})
};
Dictionary<string, List<string>> dict = myList
.GroupBy(x => x.Key, y => y)
.ToDictionary(x => x.Key, y => y.Select(z => z.Value).SelectMany(a => a).ToList());
}
}
}
I have the following dictionary:
Dictionary<string, string> clauses = new Dictionary<string, string>();
where the clauses are like this:
"A|B" - "some text"
"A|D|E" - "some text"
"G" - "some text"
"E|A" - "some text"
...
and I want to populate the dictionary below:
Dictionary<string, int> columnsBitMap = new Dictionary<string, int>();
where the string values are the unique letters of the first dictionary strings and int values are calculated by math formula.
I have the following which is working perfectly:
columnsBitMap = String.Join("|", clauses.Select(clause => clause).Select(clause => clause.Key)).Split('|')
.Distinct().OrderBy(column => column)
-- can I remove the next Select ?
.Select((column, index) => new KeyValuePair<string, int>(column, index))
.ToDictionary(column => column.Key, column => Convert.ToInt32(Math.Pow(2, column.Value)));
but I am wondering if this could be simplified removing the .Select part?
The output should be like this:
A 1
B 2
D 4
E 8
G 16
This bit is completely superfluous:
.Select(clause => clause)
Just remove it and the rest should work fine.
I dont see much reason to get rid of the part
.Select((column, index) => new KeyValuePair<string, int>(column, index))
But if you're against using a KeyValuePair<TKey,TValue> you could just make it an anonymous object
.Select((column, index) => new{ Key = column, Value = index })
But there's not a great amount of difference.
I approached your requirement in a slightly different way:
var result = clauses.SelectMany(clause => clause.Key.Split('|'))
.Distinct().OrderBy(column => column)
.Select((column, index) => new {Key=column,Value=index})
.ToDictionary(column => column.Key, column => Convert.ToInt32(Math.Pow(2, column.Value)));
Working example with your test case: http://rextester.com/PWC41147
public static IEnumerable<KeyValuePair<string, string>> GetGroupKeyValuePairs(string category)
{
var list = new List<KeyValuePair<string, string>>();
using (DataConnection connection = new DataConnection())
{
List<KeyValuePair<string,string>> settings = connection.Get<Settings>()
.Where(a => a.Category == category )
.Select(pair => new KeyValuePair<string,string>(pair.TheName, pair.TheValue))
.ToList();
list = settings;
}
return list;
}
The exception is:
InvalidOperationException:
Key 'Garanti.Oda' appears more than one time
How can I collect duplicate keys?
The method that you show isn't going to have a problem with multiple pairs with the same key. I assume that afterward, you're doing something like creating a dictionary of these pairs, and that's where you have a problem. E.g.
var pairs = GetGroupKeyValuePairs("some category");
var dict = new Dictionary<string, string>();
foreach (var pair in pairs)
dict.Add(pair.Key, pair.Value); // exception when it hits a duplicate
Instead, you need to use the pairs in a way that's friendly to duplicates, e.g. ToLookup.
var pairs = GetGroupKeyValuePairs("some category");
var lookup = pairs.ToLookup(x => x.Key, x => x.Value);
Then, for example if the list had "a", "b" and "a", "c", then lookup["a"] gives you "b" and "c".
Assuming you want to find duplicates by Key only (e.g. so that you can build a dictionary), you could GroupBy the prospective key and find all instances of more than one:
var dupeSettings = connection.Get<Settings>()
.Where(a => a.Category == category)
.GroupBy(a => a.TheName)
.Where(grp => grp.Count() > 1)
.Select(dupe => dupe.Key)
.ToList();
Or, if you want duplicates of both key and value, project and group by an anonymous class:
var dupeSettings = connection.Get<Settings>()
.Where(a => a.Category == category)
.GroupBy(a => new {a.TheName, a.TheValue})
.Where(grp => grp.Count() > 1)
.Select(dupe => dupe.Key) // Key.TheName, Key.TheValue
.ToList();
This is kind-of related to this question, on how to merge two dictionaries in C#. An elegant Linq solution is presented, which is cool.
However, that question relates to Dictionary<Object1, Object2>, whereas I have a dictionary where the value is a List<Object2>.
I am looking for a solution for merging a Dictionary<Object1, List<Object2>>, with the following requirements:
If Dictionary1 contains the same key as Dictionary2, then their List<Object2> lists should be combined. You would end up with a new key-value-pair with the shared key, and the combined lists from the two dictionaries.
If Dictionary1 contains a key that Dictionary2 doesn't then the List<Object2> list from Dictionary1 should become the value, and vice versa.
This may not be possible in Linq, or it may be worth writing it out longhand with for loops and the like, but it would be nice to have an elegant solution.
I would suggest creating your own extension method. It will be more efficient and easier to modify.
public static void MergeDictionaries<OBJ1, OBJ2>(this IDictionary<OBJ1, List<OBJ2>> dict1, IDictionary<OBJ1, List<OBJ2>> dict2)
{
foreach (var kvp2 in dict2)
{
// If the dictionary already contains the key then merge them
if (dict1.ContainsKey(kvp2.Key))
{
dict1[kvp2.Key].AddRange(kvp2.Value);
continue;
}
dict1.Add(kvp2);
}
}
The difficulty is dealing with the merging of key conflicts.
If we start by flattening all the input dictionaries using SelectMany, we can group together the elements by their key.
var result = dictionaries
.SelectMany(dict => dict)
.GroupBy(kvp => kvp.Key)
The result set contains groups where each group's key is a key from the original dictionaries, and the contents of the group are an IEnumerable<List<T>> of the lists with the same key. From these groups, we can merge all List<T> into a single IEnumerable<T> using a Select transformation with SelectMany.
var result = dictionaries
.SelectMany(dict => dict)
.GroupBy(kvp => kvp.Key)
.Select(grp => new { Key = grp.Key, Items = grp.SelectMany(list => list)})
We can then get a dictionary from this using a ToDictionary transformation, converting the IEnumerable<T> back to a List<T>.
var result = dictionaries
.SelectMany(dict => dict)
.GroupBy(kvp => kvp.Key)
.Select(grp => new { Key = grp.Key, Items = grp.SelectMany(list => list)})
.ToDictionary(kip => kip.Key, kip => new List<T>(kip.Items));
Updated in response to comment
You can populate dictionaries however you like. I have assumed it is a type which implements IEnumerable<IDictionary<TKey, List<T>>> for a TKey and T of your choosing.
The simplest way would be using a List<T> as follows:
List<IDictionary<TKey, List<T>>> dictionaries
= new List<IDictionary<TKey, List<T>>>();
dictionaries.Add(dictionary1); // Your variable
dictionaries.Add(dictionary2); // Your variable
// Add any other dictionaries here.
// Code as above!
You just need to change item merging part in solution to the previous problem.
For object we have this:
.ToDictionary(group => group.Key, group => group.First())
i.e. for duplicated items, just take the first one.
But we could use this:
.ToDictionary(group => group.Key, group => group.SelectMany(list => list).ToList());
to concatenate lists.
So, the final expression would be
var result = dictionaries.SelectMany(dict => dict)
.ToLookup(pair => pair.Key, pair => pair.Value)
.ToDictionary(group => group.Key,
group => group.SelectMany(list => list).ToList());
You could try a different merging expression if you need some extra list merging logic (e.g. only merge distinct items)
I'll be the first to admit that this is not all that pretty but this works for me.
var d1 = new Dictionary<string, List<string>>();
var d2 = new Dictionary<string, List<string>>();
d1["test"] = new List<string>() { "Stockholm", "Motala" };
d1["more"] = new List<string>() { "numerous", "populous", "bigger", "plentiful" };
d2["test"] = new List<string>() { "Washington", "Charlottesville" };
d2["less"] = new List<string>() { "insufficient", "small", "imperceptible" };
var intersect = (from key in d1.Keys.Intersect(d2.Keys) select new { Key = key, Value = new List<string>(d1[key].Concat(d2[key])) }).ToDictionary(d => d.Key, d => d.Value);
var merged = d1.Concat(d2).Where(d => !intersect.Keys.Contains(d.Key)).Concat(intersect).ToDictionary(d => d.Key, d => d.Value);