All Questions
2,851
questions
861
votes
11
answers
668k
views
IEnumerable vs List - What to Use? How do they work?
I have some doubts over how Enumerators work, and LINQ. Consider these two simple selects:
List<Animal> sel = (from animal in Animals
join race in Species
...
- 10.2k
779
votes
14
answers
861k
views
Using LINQ to remove elements from a List<T>
Say that I have LINQ query such as:
var authors = from x in authorsList
where x.firstname == "Bob"
select x;
Given that authorsList is of type List<Author>, how can ...
- 47.1k
525
votes
13
answers
513k
views
C# LINQ find duplicates in List
Using LINQ, from a List<int>, how can I retrieve a list that contains entries repeated more than once and their values?
- 5,323
403
votes
5
answers
174k
views
Flatten List in LINQ
I have a LINQ query which returns IEnumerable<List<int>> but i want to return only List<int> so i want to merge all my record in my IEnumerable<List<int>> to only one ...
- 11k
390
votes
11
answers
412k
views
Remove duplicates in the list using linq
I have a class Items with properties (Id, Name, Code, Price).
The List of Items is populated with duplicated items.
For ex.:
1 Item1 IT00001 $100
2 Item2 ...
- 59.2k
324
votes
18
answers
595k
views
Quickest way to compare two generic lists for differences
What is the quickest (and least resource intensive) to compare two massive (>50.000 items) and as a result have two lists like the ones below:
items that show up in the first list but not in the ...
- 4,009
289
votes
4
answers
821k
views
Select distinct using linq [duplicate]
I have a class list of class
public class LinqTest
{
public int id { get; set; }
public string value { get; set; }
}
List<LinqTest> myList = new List<LinqTest>();
myList.Add(new LinqTest(...
- 25.5k
254
votes
6
answers
660k
views
Get a list of distinct values in List
In C#, say I have a class called Note with three string member variables.
public class Note
{
public string Title;
public string Author;
public string Text;
}
And I have a list of type ...
- 4,546
228
votes
5
answers
454k
views
Linq select objects in list where exists IN (A,B,C)
I have a list of orders.
I want to select orders based on a set of order statuses.
So essentially select orders where order.StatusCode in ("A", "B", "C")
// Filter the orders based on the order ...
- 6,164
200
votes
13
answers
860k
views
Check if list contains element that contains a string and get that element
While searching for an answer to this question, I've run into similar ones utilizing LINQ but I haven't been able to fully understand them (and thus, implement them), as I'm not familiarized with it. ...
- 2,337
191
votes
5
answers
153k
views
How do I use LINQ to obtain a unique list of properties from a list of objects?
I'm trying to use LINQ to return a list of ids given a list of objects where the id is a property. I'd like to be able to do this without looping through each object and pulling out the unique ids ...
- 28.4k
189
votes
6
answers
281k
views
LINQ: "contains" and a Lambda query
I have a List<BuildingStatus> called buildingStatus. I'd like to check whether it contains a status whose char code (returned by GetCharCode()) equals some variable, v.Status.
Is there some way ...
- 20.8k
169
votes
10
answers
65k
views
Check whether an array is a subset of another
Any idea on how to check whether that list is a subset of another?
Specifically, I have
List<double> t1 = new List<double> { 1, 3, 5 };
List<double> t2 = new List<double> { 1,...
- 82.6k
150
votes
9
answers
533k
views
how to check if object already exists in a list
I have a list
List<MyObject> myList
and I am adding items to a list and I want to check if that object is already in the list.
so before I do this:
myList.Add(nextObject);
I want to ...
- 192k
142
votes
6
answers
113k
views
C#: How to convert a list of objects to a list of a single property of that object?
Say I have:
IList<Person> people = new List<Person>();
And the person object has properties like FirstName, LastName, and Gender.
How can I convert this to a list of properties of the ...
- 64.1k
142
votes
4
answers
202k
views
Lists: Count vs Count() [duplicate]
Given a list, which method is preferred to determine the number of elements inside?
var myList = new List<string>();
myList.Count
myList.Count()
- 5,039
138
votes
2
answers
134k
views
Easier way to populate a list with integers in .NET [duplicate]
Possible Duplicate:
Populating a list of integers in .NET
Is there a simpler or more elegant way of initializing a list of integers in C# other than this?
List<int> numberList = new List&...
The Coding Cowboy
134
votes
10
answers
103k
views
How can I get every nth item from a List<T>?
I'm using .NET 3.5 and would like to be able to obtain every *n*th item from a List. I'm not bothered as to whether it's achieved using a lambda expression or LINQ.
Edit
Looks like this question ...
- 6,573
130
votes
16
answers
163k
views
Checking if a list is empty with LINQ
What's the "best" (taking both speed and readability into account) way to determine if a list is empty? Even if the list is of type IEnumerable<T> and doesn't have a Count property.
Right now I'...
- 202k
124
votes
3
answers
62k
views
.NET List<T> Concat vs AddRange
What is the difference between the AddRange and Concat functions on a generic List? Is one recommended over the other?
- 39.8k
108
votes
10
answers
50k
views
Count property vs Count() method?
Working with a collection I have the two ways of getting the count of objects; Count (the property) and Count() (the method). Does anyone know what the key differences are?
I might be wrong, but I ...
user1017882
107
votes
7
answers
25k
views
Does Distinct() method keep original ordering of sequence intact?
I want to remove duplicates from list, without changing order of unique elements in the list.
Jon Skeet & others have suggested to use the following:
list = list.Distinct().ToList();
Reference:
...
- 2,740
106
votes
6
answers
167k
views
Freely convert between List<T> and IEnumerable<T>
How can I convert a List<MyObject> to an IEnumerable<MyObject> and then back again?
I want to do this in order to run a series of LINQ statements on the List, e. g. Sort()
- 47.1k
103
votes
10
answers
164k
views
C# Determine if List Has Duplicate
Requirement: In an unsorted List, determine if a duplicate exists.
The typical way I would do this is an n-squared nested loop. I'm wondering how others solve this. Is there an elegant, high ...
- 2,243
101
votes
7
answers
265k
views
Sorting a List<int>
Using C# what is the best way to sort a List numerically?
my list has items 5,7,3 and I would like them sorted 3,5,7. I know some longer ways, but I would imagine linq has a quicker way?
sorry this ...
- 7,077
92
votes
8
answers
175k
views
Conversion from List<T> to array T[]
Is there a short way of converting a strongly typed List<T> to an Array of the same type, e.g.: List<MyClass> to MyClass[]?
By short i mean one method call, or at least shorter than:
...
- 10.3k
91
votes
5
answers
149k
views
Simplest way to form a union of two lists
What is the easiest way to compare the elements of two lists say A and B with one another, and add the elements which are present in B to A only if they are not present in A?
To illustrate,
Take list ...
- 2,142
90
votes
8
answers
158k
views
How to check list A contains any value from list B?
List A:
1, 2, 3, 4
List B:
2, 5
How to check if list A contains any value from list B?
e.g. something like A.contains(a=>a.id = B.id)?
- 925
85
votes
7
answers
144k
views
How to get a distinct list from a List of objects?
I have a List<MyClass> someList.
class MyClass
{
public int Prop1...
public int Prop2...
public int Prop3...
}
I would like to know how to get a new distinct List<MyClass> ...
- 9,346
82
votes
11
answers
103k
views
How to Quickly Remove Items From a List
I am looking for a way to quickly remove items from a C# List<T>. The documentation states that the List.Remove() and List.RemoveAt() operations are both O(n)
List.Remove
List.RemoveAt
This ...
- 2,858
77
votes
17
answers
31k
views
Easiest way to Rotate a List in c#
Lists say I have a list List<int> {1,2,3,4,5}
Rotate means:
=> {2,3,4,5,1} => {3,4,5,1,2} => {4,5,1,2,3}
Maybe rotate is not the best word for this, but hope you understand what I ...
- 8,853
76
votes
9
answers
412k
views
How to get first object out from List<Object> using Linq
I have below code in c# 4.0.
//Dictionary object with Key as string and Value as List of Component type object
Dictionary<String, List<Component>> dic = new Dictionary<String, List<...
- 7,659
75
votes
6
answers
64k
views
How to get the closest number from a List<int> with LINQ?
How to get the closest number from a List<int> with LINQ?
For example:
List<int> numbers = new List<int>();
numbers.Add(2);
numbers.Add(5);
numbers.Add(7);
numbers.Add(10)
I need ...
- 3,381
75
votes
6
answers
40k
views
Sort one list by another
I have 2 list objects, one is just a list of ints, the other is a list of objects but the objects has an ID property.
What i want to do is sort the list of objects by its ID in the same sort order as ...
- 8,981
74
votes
5
answers
107k
views
How to find List has duplicate values in List<string> [duplicate]
How to find whether the List<string> has duplicate values or not ?
I tried with below code. Is there any best way to achieve ?
var lstNames = new List<string> { "A", "B", "A" };
if (...
- 6,473
73
votes
5
answers
81k
views
How to select values within a provided index range from a List using LINQ
I am a LINQ newbie trying to use it to acheive the following:
I have a list of ints:-
List<int> intList = new List<int>(new int[]{1,2,3,3,2,1});
Now, I want to compare the sum of the ...
- 5,116
72
votes
3
answers
61k
views
Differences between IQueryable, List, IEnumerator?
I am wondering what the difference between IQueryable, List, IEnumerator is and when I should use each one?
For instance when using Linq to SQL I would do something like this:
public List<User>...
- 84.3k
72
votes
5
answers
46k
views
C# Difference between First() and Find()
So I know that Find() is only a List<T> method, whereas First() is an extension for any IEnumerable<T>. I also know that First() will return the first element if no parameter is passed, ...
- 5,500
61
votes
3
answers
60k
views
LINQ: How to skip one then take the rest of a sequence
i would like to iterate over the items of a List<T>, except the first, preserving the order. Is there an elegant way to do it with LINQ using a statement like:
foreach (var item in list.Skip(...
- 15.4k
60
votes
5
answers
108k
views
Remove items of list from another lists with criteria
i have a list of writers.
public class Writers{
long WriterID { get;set; }
}
Also I have two lists of type Article.
public class Article{
long ArticleID { get; set; }
long WriterID { ...
- 3,841
59
votes
6
answers
128k
views
Compare Two Lists Via One Property Using LINQ
Say I have the following:
class Widget1{
public int TypeID { get; set; }
public string Color { get; set; }
}
class Widget2
{
public int TypeID { get; set; }
...
- 1,690
56
votes
5
answers
93k
views
Using LINQ to convert List<U> to List<T>
I have 2 classes which have some identical properties.
I stock into a list properties from 1st class, and after that, I want to take some needed properties and put them into a list of 2nd class type.
...
- 2,766
55
votes
10
answers
32k
views
Why is .ForEach() on IList<T> and not on IEnumerable<T>? [duplicate]
Possible Duplicate:
Why is there not a ForEach extension method on the IEnumerable interface?
I've noticed when writing LINQ-y code that .ForEach() is a nice idiom to use. For example, here is a ...
- 561
46
votes
12
answers
155k
views
compare two list and return not matching items using linq
i have a two list
List<Sent> SentList;
List<Messages> MsgList;
both have the same property called MsgID;
MsgList SentList
MsgID Content MsgID Content Stauts
1 ...
- 4,305
46
votes
2
answers
29k
views
populate a dictionary using linq
I have the following empty Dictionary
Dictionary<Guid, string> appTypeMap = new Dictionary<Guid, string>();
and the following list:
List<ApplicationType> allApplicationTypes =...
- 18.1k
43
votes
2
answers
62k
views
Get index of object in a list using Linq [duplicate]
I am new to Linq. I have a Customers table.ID,FullName,Organization,Location being the columns. I have a query in Sqlite returning me 2500 records of customers. I have to find the index of the ...
- 1,527
42
votes
4
answers
57k
views
Remove all empty elements from string array
I have this:
List<string> s = new List<string>{"", "a", "", "b", "", "c"};
I want to remove all the empty elements ("") from it quickly (probably through LINQ) without using a foreach ...
- 6,433
40
votes
7
answers
95k
views
Can I select multiple objects in a Linq query
Can I return more than one item in a select? For instance I have a List of Fixtures (think football (or soccer for the yanks) fixtures). Each fixture contains a home and away team and a home and away ...
- 12.6k
40
votes
4
answers
65k
views
Get the difference between two lists using LINQ
I have two lists and I need to compare them and only return a List of Items not in both.
var listOfIds = new List<int> {1,2,4};
var persons = new ObservableCollection<Person>
{
new ...
- 2,521
39
votes
4
answers
91k
views
Can LINQ ForEach have if statement?
Is it possible to add if-statement inside LINQ ForEach call?
sequence.Where(x => x.Name.ToString().Equals("Apple"))
.ToList()
.ForEach( /* If statement here */ );
- 2,593