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Group dictionary to other dictionary via intermediate map

I have a dictionary that map between certain keys
var map = new Dictionary<string, string>(){ {"A", "One"}, {"B", "One"}, {"C", "Two"} };
I also have a dictionary containing values
var values = new Dictionary<string, double>() { {"A", 2.0}, {"B", 1.0}, {"C", 1.0} };
I want to map the values into a third dictionary so that the value of map is the key of the new dictionary. I.e. I want the new dictionary to be
var result = new Dictionary<string, double>() {{"One", 3.0}, {"Two", 1.0}};
This can of course be achieved using loops like so
var result = new Dictionary<string, double>();
foreach (var kv in values)
{
var key = map[kv.Key];
var value = kv.Value;
if (result.TryGetValue(key, out var temp))
result[key] = value + temp;
else
result.Add(key, value);
}
Or something like that...
But is it possible to do this in a one-liner using linq?

Try this,
var result = map
.Join(values, x => x.Key, y => y.Key, (x, y) => (x.Value, y.Value))
.GroupBy(x => x.Item1)
.ToDictionary(x => x.Key, y => y.Sum(s => s.Item2));
DotNet Fiddle: https://dotnetfiddle.net/tWd9j5

Looks like you're looking for Join method
var result = map.Join(values, x => x.Key, y => y.Key, (x, y) => (x.Value, y.Value)).ToDictionary(x => x.Item1, y => y.Item2);
And to handle duplication of value
var result = map
.Join(values, x => x.Key, y => y.Key, (x, y) => (x.Value, y.Value))
.GroupBy(x => x.Item1)
.ToDictionary(x => x.Key, y => y.First().Item2);

Sure you can.
var result = (from m in map
join v in values
on m.Key equals v.Key
group v.Value by m.Value into sameVal
select new { MValue = sameVal.Key, VValue = sameVal.Sum() }).ToDictionary(a => a.MValue, b => b.VValue);

C# Get dictionary first keys of duplicated values

I've got the following Dictionary:
Dictionary<int, int> myDict = new Dictionary<int, int>();
myDict.Add(0, 6);
myDict.Add(1, 10);
myDict.Add(2, 6);
myDict.Add(3, 14);
myDict.Add(4, 10);
myDict.Add(5, 10);
I already know how to get all the duplicates values:
var duplicatedValues = myDict.GroupBy(x => x.Value).Where(x => x.Count() > 1);
But what I want instead is the following: A list with all the keys of the duplicated values, but excluding the last duplicated ones. So in my list above the duplicates values are 10 and 6, and what I want is a list of the following keys: 0, 1, 4 (so excluding 2 and 5).
What is the best way to do this?
Any help would be appreciated. Thanks in advance.
EDIT: I did manage to do it with this piece of code by modifying something I found on the internet, but to be honest I find it a bit dumb to first create a string from the keys and then back into ints. I'm kinda new to the Aggregate-command, so any help how to modify the following code would be welcome:
var lookup = allIDs.ToLookup(x => x.Value, x => x.Key).Where(x => x.Count() > 1);
foreach (var item in lookup) {
var keys = item.Aggregate("", (s, v) => s + "," + v);
string[] split = keys.Split(',');
for (int i = 0; i < split.Length - 1; i++) {
if (!split[i].Equals("")) {
Console.WriteLine("removing card nr: " + split[i]);
CurrentField.removeCardFromField(Convert.ToInt32(split[i]));
}
}
}

This should do it:
var firstKeysOfDupeValues = myDict
.GroupBy(x => x.Value)
.SelectMany(x => x.Reverse().Skip(1))
.Select(p => p.Key);
.ToList();
After grouping by value, the last key for each value group is rejected using .Reverse().Skip(1) (this construct serves double duty: it also rejects the single keys of non-duplicated values) and the keys of the remaining key/value pairs are extracted into the result.

You could use
var allButLastDupKeys = myDict.GroupBy(kv => kv.Value)
.Where(g => g.Count() > 1)
.SelectMany(g => g.Take(g.Count() - 1).Select(kv => kv.Key));
string dupKeys = string.Join(",", allButLastDupKeys); // 0,1,4

Join two dictionaries by value diffs

I have these two dictionaries:
Dictionary<char, double> analyzed_symbols = new Dictionary<char, double>();
Dictionary<char, double> decode_symbols = new Dictionary<char, double>();
I need to create another dictionary that should have their keys as key and value, like this:
Dictionary<char, char> replace_symbols = new Dictionary<char, char>();
The condition to "join" them is that difference between values should be minimal, like this:
Math.Min(Math.Abs(analyzed_symbols[key] - decode_symbols[key]))
I guess I should use LINQ for this purpose but can't figure out how to write query properly.
Data Sample:
analyzed_symbols = [a, 173], [b, 1522], [z, 99]
decode_symbols = [в, 100], [д, 185], [e, 1622]
For these dicts output data should look like this:
replace_symbols = [z, в], [b, е], [a, д]
I've found question that is pretty close to what I need, but not exactly. Snowy asks there about one close value, but I need to do the same thing for two dictionaries.

This is my take on it:
var analyzed_symbols = new Dictionary<char, double>(){ {'a', 173}, {'b', 1522}, {'z', 99} };
var decode_symbols = new Dictionary<char, double>(){ {'в', 100}, {'д', 185}, {'e', 1622} };
var q = from a in analyzed_symbols
from d in decode_symbols
let tmp = new { A = a.Key, D = d.Key, Value = Math.Abs(a.Value - d.Value) }
group tmp by tmp.A into g
select new
{
Key = g.Key,
Value = g.OrderBy (x => x.Value).Select (x => x.D).First()
};
var replace_symbols = q.ToDictionary (x => x.Key, x => x.Value);

Okay, I'll try. I divided into several queries, because it's more readable that way.
//sorting values of the dictionaries to easily get closest
var analyzedSortedValues = analyzed_symbols.Values.OrderBy(k => k);
var decodeSortedValues = decode_symbols.Values.OrderBy(k => k);
//creating pairs of the closest values. Here I use iterator index i to skip
//some values that have been used already (is it correct?)
var t = analyzedSortedValues.Select((k, i) => new { a = k, d = decodeSortedValues.Skip(i).Any() ? decodeSortedValues.Skip(i).First() : -1 });
//printing results by getting appropriate keys from corresponding dictionaries
foreach (var item in t)
{
Console.WriteLine("[{0}, {1}]", analyzed_symbols.FirstOrDefault(kvp => kvp.Value == item.a).Key, decode_symbols.FirstOrDefault(kvp => kvp.Value == item.d).Key);
}

I am not exactly sure how to do it via LINQ but here is the longhand version of what you want to do.
private static Dictionary<char, char> BuildReplacementDictionary(Dictionary<char, double> analyzedSymbols,
Dictionary<char, double> decodeSymbols)
{
Dictionary<char, char> replaceSymbols = new Dictionary<char, char>(analyzedSymbols.Count);
foreach (KeyValuePair<char, double> analyzedKvp in analyzedSymbols)
{
double bestMatchValue = double.MaxValue;
foreach (KeyValuePair<char, double> decodeKvp in decodeSymbols)
{
var testValue = Math.Abs(analyzedKvp.Value - decodeKvp.Value);
if (testValue <= bestMatchValue)
{
bestMatchValue = testValue;
replaceSymbols[analyzedKvp.Key] = decodeKvp.Key;
}
}
}
return replaceSymbols;
}
What it does is it goes through each element of the analyzed dictionary, test every element of the decoded dictionary, and if that match is the same or better than the previous match it found it will use the new value from the decoded dictionary.

Checking a dictionary if there are same values for a key

I have a dictionary object like this:
CustomKeys<int, string>
eg;
1000, F1
1001, F2
1002, F1
1003, F4
1004, F2
I want to know if I have more than 1 of same values in this dictionary. I would also want to keep a note of which keys(unique id) has duplicates.
Is that possible?

It is possible using GroupBy and than Count() > 1 to keep track of which values that have duplicates.
var q = dic.GroupBy(x => x.Value)
.Select (x => new { Item = x, HasDuplicates = x.Count() > 1 });

You can find all key values they had the same values like this;
Dictionary<int, string> d = new Dictionary<int, string>();
d.Add(1000, "F1");
d.Add(1001, "F2");
d.Add(1002, "F1");
d.Add(1003, "F4");
d.Add(1004, "F2");
var dublicate = d.ToLookup(x => x.Value, x => x.Key).Where(x => x.Count() > 1);
foreach (var i in dublicate)
{
Console.WriteLine(i.Key);
}
Here is a DEMO.
But if you want to get a boolean value since your item's has a same value, look at Magnus's answer which is great.

I'm not sure by what you mean by "keeping note of which has duplicate values". If you mean keeping note of the keys, you could do this:
var keys = new Dictionary<int, string>();
keys.Add(1000, "F1");
keys.Add(1001, "F2");
keys.Add(1002, "F1");
keys.Add(1003, "F4");
keys.Add(1004, "F2");
var duplicates = keys.GroupBy(i => i.Value).Select(i => new
{
keys = i.Select(x => x.Key),
value = i.Key,
count = i.Count()
});
foreach (var duplicate in duplicates)
{
Console.WriteLine("Value: {0} Count: {1}", duplicate.value, duplicate.count);
foreach (var key in duplicate.keys)
{
Console.WriteLine(" - {0}", key);
}
}
If you mean keeping track of the duplicate values only, see Sonor's answer.

Another solution could be:
var duplicates = dictionary.GroupBy( g => g.Value )
.Where( x => x.Count( ) > 1 )
.Select( x => new { Item = x.First( ), Count = x.Count( ) } )
.ToList( );

How to convert List<String> to Dictionary<int,String>

I have List<String>, i need to convert it to Dictionary<int,String> with auto generation of Key, is any shortest way to accomplish that? I have tried:
var dictionary = new Dictionary<int, String>();
int index = 0;
list.ForEach(x=>{
definitions.Add(index, x);
index++;
});
but i think it is dirty way.

var dict = list.Select((s, i) => new { s, i }).ToDictionary(x => x.i, x => x.s);

I find this to be the neatest
int index = 0;
var dictionary = myList.ToDictionary(item => index++);

In my opinion, what you have is more readable than the Linq way (and as a bonus, it happens to be more efficient):
foreach(var item in list)
dictionary[index++] = item;

Use:
var dict = list.Select((x, i) => new {x, i})
.ToDictionary(a => a.i, a => a.x);