I have a problem with a query. I have a List with int and want to use it to get the values from my dictionary. The dictionary-keys are int and some of them have the value of the list-items. My question is how i get the objects out of the dictionary, thats keys matces the list items. Was programming JAVA the last years and now struggling with LINQ :(
Thanks in advance
Problem solved. Thank you all :)
No idea how to close this topic. I am reading stackoverflow since one year, but this was my first post.
You can use Linq to join list items with dictionary KeyValuePair entries on entry key. And then select entry value from each joined pair:
var values = from l in list
join kvp in dictionary on l equals kvp.Key
select kvp.Value;
Lambda syntax:
var values = list.Join(dictionary, l => l, kvp => kvp.Key, (l,kvp) => kvp.Value);
Basically:
var value = dictionary[integerKey];
Or:
if (dictionary.TryGetValue(integerKey, out value)) {
}
You can also create an extension method:
public static class DictionaryExtensions
{
public static IEnumerable<TValue> FilterValuesBy<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, IEnumerable<TKey> filter)
{
if (dictionary == null) throw new ArgumentNullException("dictionary");
if (filter == null) throw new ArgumentNullException("filter");
var coll = filter as ICollection<TKey> ?? new HashSet<TKey>(filter);
return dictionary.Where(kvp => coll.Contains(kvp.Key)).Select(kvp => kvp.Value);
}
}
Usage:
class Program
{
static void Main()
{
var dict = Enumerable.Range(0, 10).ToDictionary(x => x);
var filter = Enumerable.Range(0, 2);
foreach (var i in dict.FilterValuesBy(filter))
{
Console.WriteLine(i);
}
Console.ReadLine();
}
}
Simple Linq method chain:
var dict = Enumerable.Range(0, 10).ToDictionary(x => x);
var filter = Enumerable.Range(0, 2).ToList();
var filtered = dict.Where(x => filter.Contains(x.Key)).Select(x => x.Value).ToList();
Related
***ctx.Load(listItemCollection,
eachItem => eachItem.Include(
item => item,
item => item["Column1"],
item => item["Column2"]
));***
i have list of fields in a array of string instead of column1 and column2, how can i pass it through in include linq, not able to create proper lambda on runtime. i tried following ways but couldn't get success. Static befor loops works but thw fields added in loop fails as it doesn't evaluate string value in loop
***Expression<Func<ListItem, object>>[] paramss = new
Expression<Func<ListItem, object>>[length];
paramss[0] = x => x.ContentType;
paramss[1] = x => x["Title"];
count = 2;
foreach (string item in solConnDefModel.Columns)
{ paramss[count] = x => x[item];
count++;
}***
Please take a reference of below code:
List dlist = context.Web.Lists.GetByTitle("listname");
context.Load(dlist);
context.ExecuteQuery();
string[] fieldNames = { "Id", "Title", "num", "mStartDate" };
// Create the expression used to define the fields to be included
List<Expression<Func<ListItemCollection, object>>> fieldsToBeIncluded = new List<Expression<Func<ListItemCollection, object>>>();
foreach (string s in fieldNames)
{
fieldsToBeIncluded.Add(items => items.Include(item => item[s]));
}
// Initialize the collection of list items
var listItems = dlist.GetItems(new CamlQuery());
context.Load(listItems, fieldsToBeIncluded.ToArray());
context.ExecuteQuery();
You can hover on load method to see what type parameter it requires, then generate a corresponding one and pass it.
i have to create lambda expression at runtime. following code i was able to get expected value
Expression<Func<ListItem, object>>[] paramss = new Expression<Func<ListItem, object>>[length];
foreach (string item in Columns)
{
if (item.ToLower() != "contenttype")
{
ParameterExpression parameter = Expression.Parameter(typeof(ListItem), "x");
var propertyInfo = typeof(ListItem).GetMethod("get_Item");
var arguments = new List<Expression> { Expression.Constant(item) };
var expression = Expression.Call(parameter, propertyInfo, arguments);
var lambda = Expression.Lambda<Func<ListItem, object>>(expression, parameter);
paramss[count] = lambda;
}
else
{
paramss[count] = x => x.ContentType;
}
count++;
}
I've written a Linq sentence like this:
var fs = list
.GroupBy(i =>
new {
X = i.X,
Ps = i.Properties.Where(p => p.Key.Equals("m")) <<<<<<<<<<<
}
)
.Select(g => g.Key });
Am I able to group by IEnumerable.Where(...) fields?
The grouping won't work here.
When grouping, the runtime will try to compare group keys in order to produce proper groups. However, since in the group key you use a property (Ps) which is a distinct IEnumerable<T> for each item in list (the comparison is made on reference equality not on sequence equality) this will result in a different collection for each element; in other words if you'll have two items:
var a = new { X = 1, Properties = new[] { "m" } };
var b = new { X = 1, Properties = new[] { "m" } };
The GroupBy clause will give you two distinct keys as you can see from the image below.
If your intent is to just project the items into the structure of the GroupBy key then you don't need the grouping; the query below should give the same result:
var fs = list.Select(item => new
{
item.X,
Ps = item.Properties.Where(p => p.Key == "m")
});
However, if you do require the results to be distinct, you'll need to create a separate class for your result and implement a separate IEqualityComparer<T> to be used with Distinct clause:
public class Result
{
public int X { get; set; }
public IEnumerable<string> Ps { get; set; }
}
public class ResultComparer : IEqualityComparer<Result>
{
public bool Equals(Result a, Result b)
{
return a.X == b.X && a.Ps.SequenceEqual(b.Ps);
}
// Implement GetHashCode
}
Having the above you can use Distinct on the first query to get distinct results:
var fs = list.Select(item => new Result
{
X = item.X,
Ps = item.Properties.Where( p => p.Key == "m")
}).Distinct(new ResultComparer());
i have a dictionary defined as follows:
Dictionary<string, int> Controls = new Dictionary<string, int>();
using the following code i am putting keys which have similar value into var
var result = (from p in Controls
group p by p.Value into g
where g.Count() > 1
select g);
But neither i am able to convert 'result' into dictionary again or nor i am able to access item inside 'result'
i tried this code but
foreach (System.Linq.Lookup<int, KeyValuePair<string, int>> Item in result)
{
}
Plz help.
try this:
var dict = result.ToDictionary(x => x.Key, x => x.Select(y => y.Key).ToList())
and access it like
foreach(var item in dict)
BTW, there's no type var. It's just instruction for the compiler to determine type for variable, but it's strongly typed. In your case, I think, it would be IEnumerable<IGrouping<TKey, TSource>>. Actually you can access result like this too:
foreach(var item in result)
{
// item is type Lookup<int, KeyValuePair<string, int>>.Grouping
// you can go through item like
foreach(var i in item)
{
}
// or convert it ToList()
var l = item.ToList()
// l is type List<KeyValuePair<string, int>>
}
I'm building a word anagram program that uses a database which contains one simple table:
Words
---------------------
varchar(15) alphagram
varchar(15) anagram
(other fields omitted for brevity)
An alphagram is the letters of a word arranged in alphabetical order. For example, the alphagram for OVERFLOW would be EFLOORVW. Every Alphagram in my database has one or more Anagrams. Here's a sample data dump of my table:
Alphagram Anagram
EINORST NORITES
EINORST OESTRIN
EINORST ORIENTS
EINORST STONIER
ADEINRT ANTIRED
ADEINRT DETRAIN
ADEINRT TRAINED
I'm trying to build a LINQ query that would return a list of Alphagrams along with their associated Anagrams. Is this possible?
UPDATE: Here's my solution based on the suggestions below! Thanks all!
using (LexiconEntities ctx = new LexiconEntities())
{
var words = ctx.words;
var query =
from word in words
where word.alphagram == "AEINRST"
group word by word.alphagram into alphagramGroup
select new { Alphagram = alphagramGroup.Key, Anagrams = alphagramGroup };
foreach (var alphagramGroup in query)
{
Console.WriteLine("Alphagram: {0}", alphagramGroup.Alphagram);
foreach (var anagram in alphagramGroup.Anagrams)
{
Console.WriteLine("Anagram: {0}", anagram.word1);
}
}
}
var list = anagrams.Select(
a => new {
Alphagram = a.ToCharArray().OrderBy(s => s).ToString(),
Anagram = a
}).toList();
A totally new answer...
You seem to need a groupby query look at How to: Group Data (Entity Framework).
this should accomplish what you want...
I did a testy with LINQ and this works...
var words = new List<Word>()
{
new ConsoleApplication1.Word("EINORST", "NORITES"),
new ConsoleApplication1.Word("EINORST", "OESTRIN"),
new ConsoleApplication1.Word("EINORST", "STONIER"),
new ConsoleApplication1.Word("ADEINRT", "ANTIRED"),
new ConsoleApplication1.Word("ADEINRT", "DETRAIN"),
new ConsoleApplication1.Word("ADEINRT", "TRAINED")
};
var q = words.GroupBy(w => w.Alphagram).Select(w => new { Alphagram = w.Key, Anagrams = w.Select(p => p.Anagram).ToList() }).ToList();
foreach (var item in q)
{
Console.WriteLine("Alphagram : {0}, Anagrams = {1}", item.Alphagram, String.Join(",", item.Anagrams));
}
var words = new List<Words>()
{
new Words("EINORST", "NORITES"),
new Words("EINORST", "OESTRIN"),
new Words("EINORST", "STONIER"),
new Words("ADEINRT", "ANTIRED"),
new Words("ADEINRT", "DETRAIN"),
new Words("ADEINRT", "TRAINED")
};
var result = words.GroupBy(w => w.Alphagram, w => w.Anagram)
.Select(w => new {
Alphagram = w.Key,
Anagrams = w.Where(p => w.Key.ToCharArray().SequenceEqualUnOrdered(p.ToCharArray())).ToList()
}
)
.ToList();
public static bool SequenceEqualUnOrdered<T>(this IEnumerable<T> first, IEnumerable<T> second)
{
return new HashSet<T>(first).SetEquals(second);
}
Is it what you are looking for? It is LINQ to Objects. You may want to use LINQ-to-SQL or LINQ-to-Entites to fetch your records into your objects and then use the above-mentioned LINQ-to-Objects query over the already-fetched object collection.
I have got a collection. The coll has strings:
Location="Theater=1, Name=regal, Area=Area1"
Location="Theater=34, Name=Karm, Area=Area4445"
and so on. I have to extract just the Name bit from the string. For example, here I have to extract the text 'regal' and group the query. Then display the result as
Name=regal Count 33
Name=Karm Count 22
I am struggling with the query:
Collection.Location.GroupBy(????);(what to add here)
Which is the most short and precise way to do it?
Yet another Linq + Regex approach:
string[] Location = {
"Theater=2, Name=regal, Area=Area1",
"Theater=2, Name=regal, Area=Area1",
"Theater=34, Name=Karm, Area=Area4445"
};
var test = Location.Select(
x => Regex.Match(x, "^.*Name=(.*),.*$")
.Groups[1].Value)
.GroupBy(x => x)
.Select(x=> new {Name = x.Key, Count = x.Count()});
Query result for tested strings
Once you've extracted the string, just group by it and count the results:
var query = from location in locations
let name = ExtractNameFromLocation(location)
group 1 by name in grouped
select new { Name=grouped.Key, Count=grouped.Count() };
That's not particularly efficient, however. It has to do all the grouping before it does any counting. Have a look at this VJ article for an extension method for LINQ to Objects,
and this one about Push LINQ which a somewhat different way of looking at LINQ.
EDIT: ExtractNameFromLocation would be the code taken from answers to your other question, e.g.
public static string ExtractNameFromLocation(string location)
{
var name = (from part in location.Split(',')
let pair = part.Split('=')
where pair[0].Trim() == "Name"
select pair[1].Trim()).FirstOrDefault();
return name;
}
Here is another LINQ alternative solution with a working example.
static void Main(string[] args)
{
System.Collections.Generic.List<string> l = new List<string>();
l.Add("Theater=1, Name=regal, Area=Area"); l.Add("Theater=34, Name=Karm, Area=Area4445");
foreach (IGrouping<string, string> g in l.GroupBy(r => extractName(r)))
{
Console.WriteLine( string.Format("Name= {0} Count {1}", g.Key, g.Count()) );
}
}
private static string extractName(string dirty)
{
System.Text.RegularExpressions.Match m =
System.Text.RegularExpressions.Regex.Match(
dirty, #"(?<=Name=)[a-zA-Z0-9_ ]+(?=,)");
return m.Success ? m.Value : "";
}