All Questions
15,560
questions
1716
votes
29
answers
251k
views
Why not inherit from List<T>?
When planning out my programs, I often start with a chain of thought like so:
A football team is just a list of football players. Therefore, I should represent it with:
var football_team = new ...
- 26k
1636
votes
24
answers
1.8m
views
How to Sort a List<T> by a property in the object
I have a class called Order which has properties such as OrderId, OrderDate, Quantity, and Total. I have a list of this Order class:
List<Order> objListOrder = new List<Order>();
...
- 216k
1125
votes
32
answers
678k
views
Randomize a List<T>
What is the best way to randomize the order of a generic list in C#? I've got a finite set of 75 numbers in a list I would like to assign a random order to, in order to draw them for a lottery type ...
- 14.1k
890
votes
3
answers
992k
views
C# List<string> to string with delimiter
Is there a function in C# to quickly convert some collection to string and separate values with delimiter?
For example:
List<string> names --> string names_together = "John, Anna, Monica"
- 20k
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
757
votes
30
answers
902k
views
How do I clone a generic list in C#?
I have a generic list of objects in C#, and wish to clone the list. The items within the list are cloneable, but there doesn't seem to be an option to do list.Clone().
Is there an easy way around ...
- 7,877
637
votes
32
answers
849k
views
Remove duplicates from a List<T> in C#
Anyone have a quick method for de-duplicating a generic List in C#?
- 39.7k
610
votes
28
answers
562k
views
How to remove elements from a generic list while iterating over it?
I am looking for a better pattern for working with a list of elements which each need processed and then depending on the outcome are removed from the list.
You can't use .Remove(element) inside a ...
- 10.8k
561
votes
18
answers
239k
views
List<T> or IList<T> [closed]
Can anyone explain to me why I would want to use IList over List in C#?
Related question: Why is it considered bad to expose List<T>
- 19.2k
560
votes
14
answers
1.2m
views
How to initialize a list of strings (List<string>) with many string values
How is it possible to initialize (with a C# initializer) a list of strings? I have tried with the example below but it's not working.
List<string> optionList = new List<string>
{
"...
- 8,867
530
votes
5
answers
335k
views
How to add item to the beginning of List<T>?
I want to add a "Select One" option to a drop down list bound to a List<T>.
Once I query for the List<T>, how do I add my initial Item, not part of the data source, as the FIRST element ...
- 9,731
508
votes
17
answers
858k
views
How can I add an item to a IEnumerable<T> collection?
My question as title above. For example
IEnumerable<T> items = new T[]{new T("msg")};
items.ToList().Add(new T("msg2"));
but after all it only has 1 item inside. Can we have ...
- 5,965
500
votes
12
answers
478k
views
ArrayList vs List<> in C#
What is the difference between ArrayList and List<> in C#?
Is it only that List<> has a type while ArrayList doesn't?
- 14.3k
485
votes
10
answers
796k
views
List<T> OrderBy Alphabetical Order
I'm using C# on Framework 3.5. I'm looking to quickly sort a Generic List<T>. For the sake of this example, let's say I have a List of a Person type with a property of lastname. How would I ...
- 9,845
461
votes
6
answers
1.2m
views
Getting a list item by index
I've recently started using c# moving over from Java. I can't seem to find how to get a list item by index. In java to get the first item of the list it would be:
list1.get(0);
What is the ...
- 4,659
409
votes
8
answers
462k
views
How to easily initialize a list of Tuples?
I love tuples. They allow you to quickly group relevant information together without having to write a struct or class for it. This is very useful while refactoring very localized code.
Initializing a ...
- 18.8k
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
379
votes
10
answers
558k
views
How do I copy items from list to list without foreach?
How do I transfer the items contained in one List to another in C# without using foreach?
- 13.3k
360
votes
15
answers
594k
views
Merge two (or more) lists into one, in C# .NET
Is it possible to convert two or more lists into one single list, in .NET using C#?
For example,
public static List<Product> GetAllProducts(int categoryId){ .... }
.
.
.
var ...
- 4,677
357
votes
5
answers
587k
views
Converting from IEnumerable to List [duplicate]
I want to convert from IEnumerable<Contact> to List<Contact>. How can I do this?
- 17.7k
350
votes
14
answers
435k
views
List of Timezone IDs for use with FindTimeZoneById() in C#?
Can someone please point me to a complete list of all the timezones referenced by the id expected in TimeZoneInfo.FindTimeZoneById()? I can't find a list anywhere and I've looked through the .NET ...
- 3,764
340
votes
11
answers
668k
views
Conversion of System.Array to List
Last night I had dream that the following was impossible. But in the same dream, someone from SO told me otherwise. Hence I would like to know if it it possible to convert System.Array to List
Array ...
- 3,971
333
votes
21
answers
382k
views
Split a List into smaller lists of N size [duplicate]
I am attempting to split a list into a series of smaller lists.
My Problem: My function to split lists doesn't split them into lists of the correct size. It should split them into lists of size 30 ...
- 25.4k
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
312
votes
29
answers
612k
views
Convert generic List/Enumerable to DataTable?
I have few methods that returns different Generic Lists.
Exists in .net any class static method or whatever to convert any list into a datatable? The only thing that i can imagine is use Reflection ...
- 4,668
307
votes
7
answers
709k
views
Getting all file names from a folder using C# [duplicate]
I wanted to know if it is possible to get all the names of text files in a certain folder.
For example, I have a folder with the name Maps, and I would like to get the names of all the text files in ...
- 3,271
306
votes
15
answers
559k
views
Convert a list to a string in C#
How do I convert a list to a string in C#?
When I execute toString on a List object, I get:
System.Collections.Generic.List`1[System.String]
- 63.3k
294
votes
9
answers
324k
views
Compare two List<T> objects for equality, ignoring order [duplicate]
Yet another list-comparing question.
List<MyType> list1;
List<MyType> list2;
I need to check that they both have the same elements, regardless of their position within the list. Each ...
- 3,129
291
votes
8
answers
237k
views
Shorter syntax for casting from a List<X> to a List<Y>?
I know it's possible to cast a list of items from one type to another (given that your object has a public static explicit operator method to do the casting) one at a time as follows:
List<Y> ...
- 22.7k
291
votes
10
answers
961k
views
How to remove item from list in C#?
I have a list stored in resultlist as follows:
var resultlist = results.ToList();
It looks something like this:
ID FirstName LastName
-- --------- --------
1 Bill Smith
2 John ...
- 45.2k
291
votes
11
answers
302k
views
Remove items from one list in another
I'm trying to figure out how to traverse a generic list of items that I want to remove from another list of items.
So let's say I have this as a hypothetical example
List<car> list1 = ...
- 47.1k
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
269
votes
11
answers
392k
views
How can I convert comma separated string into a List<int> [duplicate]
string tags = "9,3,12,43,2"
List<int> TagIds = tags.Split(',');
This doesn't work cause the split method returns a string[]
- 5,846
254
votes
11
answers
295k
views
Split string, convert ToList<int>() in one line
I have a string that has numbers
string sNumbers = "1,2,3,4,5";
I can split it then convert it to List<int>
sNumbers.Split( new[] { ',' } ).ToList<int>();
How can I convert string ...
- 16.3k
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
250
votes
13
answers
149k
views
Convert List<DerivedClass> to List<BaseClass>
While we can inherit from base class/interface, why can't we declare a List<>
using same class/interface?
interface A
{ }
class B : A
{ }
class C : B
{ }
class Test
{
static void Main(...
- 21.7k
246
votes
12
answers
648k
views
How can I find the last element in a List<>?
The following is an extract from my code:
public class AllIntegerIDs
{
public AllIntegerIDs()
{
m_MessageID = 0;
m_MessageType = 0;
m_ClassID = 0;
...
- 7,215
233
votes
14
answers
386k
views
Check if a string contains an element from a list (of strings)
For the following block of code:
For I = 0 To listOfStrings.Count - 1
If myString.Contains(lstOfStrings.Item(I)) Then
Return True
End If
Next
Return False
The output is:
Case 1:
...
- 3,374
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
224
votes
8
answers
413k
views
How do I get the list of keys in a Dictionary?
I only want the Keys and not the Values of a Dictionary.
I haven't been able to get any code to do this yet. Using another array proved to be too much work as I use remove also.
How do I get a List of ...
- 7,709
221
votes
8
answers
204k
views
Case-Insensitive List Search
I have a list testList that contains a bunch of strings. I would like to add a new string into the testList only if it doesn't already exist in the list. Therefore, I need to do a case-insensitive ...
- 2,717
218
votes
6
answers
323k
views
How do you concatenate Lists in C#?
If I have:
List<string> myList1;
List<string> myList2;
myList1 = getMeAList();
// Checked myList1, it contains 4 strings
myList2 = getMeAnotherList();
// Checked myList2, it contains 6 ...
- 5,339
213
votes
7
answers
249k
views
How can I add to a List's first position? [duplicate]
I just have a List<T> and I would like to add an item to this list but at the first position.
MyList.add() adds the item as the last. How can I add it as the first?.
Thanks for help!
- 13.5k
213
votes
6
answers
213k
views
How to merge 2 List<T> and removing duplicate values from it in C#
I have two lists List that I need to combine in third list and remove duplicate values from that lists
A bit hard to explain, so let me show an example of what the code looks like and what I want as ...
- 14.7k
211
votes
9
answers
543k
views
How to split() a delimited string to a List<String>
I had this code:
String[] lineElements;
. . .
try
{
using (StreamReader sr = new StreamReader("TestFile.txt"))
{
String line;
while ((...
210
votes
4
answers
188k
views
Create an array or List of all dates between two dates [duplicate]
I am generating multi-series graphs with the date along the X-Axis.
The problem is that not all of the series in the graph have the same dates in the date range. Meaning that if I choose 1 Feb ...
- 7,067
209
votes
4
answers
297k
views
C# List of objects, how do I get the sum of a property
I have a list of objects. One property of the individual object entry is amount. How do I get the sum of amount?
If my list was of type double I may be able to do something like this:
double total = ...
- 4,507
205
votes
9
answers
531k
views
Check if list is empty in C#
I have a generic list object. I need to check if the list is empty.
How do I check if a List<T> is empty in C#?
- 2,415