I have list of integer and I am trying to sort this based on first in descending order and after that I want to sort with in two list based on even and odds but still in descending order like this
using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
var numbers = new List<int>() { 3, 7, 1, 5, 4, 6, 2 };
var sortedDescendingNumbers = numbers.OrderByDescending(x => x);
var sortedNumbers = sortedDescendingNumbers.ThenByDescending(x => x % 2 == 0);
foreach (var num in sortedNumbers)
{
Console.Write(num + " ");
}
}
}
but this one print the result as 7 6 5 4 3 2 1 and I am expecting output like 7 5 3 1 6 4 2
Your first block of numbers should be the odd ones, so you have to order by divisibility by 2 first and then by descending value.
var sortedOddEvenNumbers = numbers.OrderBy(x => x % 2 == 0);
var sortedNumbers = sortedOddEvenNumbers.ThenByDescending(x => x);
I have an unsorted list of ints:
1 3 1 2 4 3 2 1
I need to sort it, and before each group of equal numbers, insert a 0:
0 1 1 1 0 2 2 0 3 3 0 4
Is there a way to get from the first list to the second list with just one LINQ statement? I'm stuck at
from num in numbers
orderby num
select num
followed by a foreach loop that manually constructs the final output based on these results. I'd like to eliminate the second loop entirely, if possible.
Try:
list.GroupBy(n => n)
.OrderBy(g => g.Key)
.SelectMany(g => new[] { 0 }.Concat(g))
For each group of numbers, prepend 0, and then flatten the list with SelectMany.
And in query syntax:
from num in list
group num by num into groupOfNums
orderby groupOfNums.Key
from n in new[] { 0 }.Concat(groupOfNums)
select n
int[] nums = { 1, 3, 1, 2, 4, 3 ,2 ,1};
var newlist = nums.GroupBy(x => x)
.OrderBy(x=>x.Key)
.SelectMany(g => new[] { 0 }.Concat(g)).ToList();
Try this out on LinqPad.
var list = new int[]{1, 3, 1, 2, 4, 3, 2, 1};
var q = from x in list
orderby x
group x by x into xs
from y in (new int[]{0}).Concat(xs)
select y;
q.Dump();
This should give you the desired result.
I have a list using this Linq query
filterEntities = (from list in filterEntities where list.Id== 0 && list.Id== 1 && list.Id == 3 && list.Id== 6 select list).OrderBy(r => r.Id).ToList();
Now this linq returns a list like
ID Age
0 18
0 19
1 21
3 24
6 32
6 08
I want to generate a list using sum of same Id's which returns like
ID Age
0 37
1 21
3 24
6 40
Please suggest me possible query
I think you are looking to use a group by like this
List<int> ids = new List<int>() { 0, 1, 3, 6 };
filterEntities = (from list in filterEntities
where ids.Contains(list.Id)
group list by list.id into g
orderby g.Key
select new
{
ID = g.Key,
Age = g.Sum(x => x.Age),
}).ToList();
I would clean up the query like this, because the long expression looks a bit confusing:
var idList = new List<int> { 0, 1, 3, 6};
filterEntities = from e in filterEntities
where idList.Contains(e.Id)
group e by e.Id into g
select new { Id = g.Key, Sum = g.Sum(e =>e.Age) };
filterEntities = filterEntities.Where(l=>new[] { 0, 1, 3, 6 }.Contains(l.Id))
.Sum(c=>c.Age)
.GroupBy(r=>r.Id)
.ToList();
Okay, so this seems simple, but I can't think of a straightforward solution;
Basically I have an object array in C# that contains, say, 102 elements. I then also have 4 other empty arrays. I want to iterate through the original array and distribute the 100 elements evenly, then distribute 101 and 102 to the 1st and 2nd new arrays respectively.
int i = 1,a=0, b=0, c=0, d = 0;
foreach (ReviewStatus data in routingData)
{
if (i == 1)
{
threadOneWork[a] = data;
a++;
}
if (i == 2)
{
threadTwoWork[b] = data;
b++;
}
if (i == 3)
{
threadThreeWork[c] = data;
c++;
}
if (i == 4)
{
threadFourWork[d] = data;
d++;
i = 0;
}
i++;
}
Now the above code definitely works, but I was curious, does anybody know of a better way to do this??
var workArrays = new[] {
threadOneWork,
threadTwoWork,
threadThreeWork,
threadFourWork,
};
for(int i=0; i<routingData.Length; i++) {
workArrays[i%4][i/4] = routingData[i];
}
Put the four arrays into an array of arrays, and use i%4 as an index. Assuming that thread###Work arrays have enough space to store the data, you can do this:
var tw = new[] {threadOneWork, threadTwoWork, threadThreeWork, threadFourWork};
var i = 0;
foreach (ReviewStatus data in routingData) {
tw[i%4][i/tw.Length] = data;
i++;
}
Linq is your friend! Use modulo to group the items via the total number of arrays in your case 4.
For example the code splits them up into four different lists:
var Items = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
Items.Select( ( i, index ) => new {
category = index % 4,
value = i
} )
.GroupBy( itm => itm.category, itm => itm.value )
.ToList()
.ForEach( gr => Console.WriteLine("Group {0} : {1}", gr.Key, string.Join(",", gr)));
/* output
Group 0 : 1,5,9
Group 1 : 2,6,10
Group 2 : 3,7
Group 3 : 4,8
*/
If I have two lists of type string (or any other type), what is a quick way of joining the two lists?
The order should stay the same. Duplicates should be removed (though every item in both links are unique). I didn't find much on this when googling and didn't want to implement any .NET interfaces for speed of delivery.
You could try:
List<string> a = new List<string>();
List<string> b = new List<string>();
a.AddRange(b);
MSDN page for AddRange
This preserves the order of the lists, but it doesn't remove any duplicates (which Union would do).
This does change list a. If you wanted to preserve the original lists then you should use Concat (as pointed out in the other answers):
var newList = a.Concat(b);
This returns an IEnumerable as long as a is not null.
The way with the least space overhead is to use the Concat extension method.
var combined = list1.Concat(list2);
It creates an instance of IEnumerable<T> which will enumerate the elements of list1 and list2 in that order.
The Union method might address your needs. You didn't specify whether order or duplicates was important.
Take two IEnumerables and perform a union as seen here:
int[] ints1 = { 5, 3, 9, 7, 5, 9, 3, 7 };
int[] ints2 = { 8, 3, 6, 4, 4, 9, 1, 0 };
IEnumerable<int> union = ints1.Union(ints2);
// yields { 5, 3, 9, 7, 8, 6, 4, 1, 0 }
Something like this:
firstList.AddRange (secondList);
Or, you can use the 'Union' extension method that is defined in System.Linq.
With 'Union', you can also specify a comparer, which can be used to specify whether an item should be unioned or not.
Like this:
List<int> one = new List<int> { 1, 2, 3, 4, 5 };
List<int> second=new List<int> { 1, 2, 5, 6 };
var result = one.Union (second, new EqComparer ());
foreach( int x in result )
{
Console.WriteLine (x);
}
Console.ReadLine ();
#region IEqualityComparer<int> Members
public class EqComparer : IEqualityComparer<int>
{
public bool Equals( int x, int y )
{
return x == y;
}
public int GetHashCode( int obj )
{
return obj.GetHashCode ();
}
}
#endregion
targetList = list1.Concat(list2).ToList();
It's working fine I think so. As previously said, Concat returns a new sequence and while converting the result to List, it does the job perfectly. Implicit conversions may fail sometimes when using the AddRange method.
If some item(s) exist in both lists you may use
var all = list1.Concat(list2).Concat(list3) ... Concat(listN).Distinct().ToList();
As long as they are of the same type, it's very simple with AddRange:
list2.AddRange(list1);
var bigList = new List<int> { 1, 2, 3 }
.Concat(new List<int> { 4, 5, 6 })
.ToList(); /// yields { 1, 2, 3, 4, 5, 6 }
The AddRange method
aList.AddRange( anotherList );
List<string> list1 = new List<string>();
list1.Add("dot");
list1.Add("net");
List<string> list2 = new List<string>();
list2.Add("pearls");
list2.Add("!");
var result = list1.Concat(list2);
one way: List.AddRange() depending on the types?
One way, I haven't seen mentioned that can be a bit more robust, particularly if you wanted to alter each element in some way (e.g. you wanted to .Trim() all of the elements.
List<string> a = new List<string>();
List<string> b = new List<string>();
// ...
b.ForEach(x=>a.Add(x.Trim()));
See this link
public class ProductA
{
public string Name { get; set; }
public int Code { get; set; }
}
public class ProductComparer : IEqualityComparer<ProductA>
{
public bool Equals(ProductA x, ProductA y)
{
//Check whether the objects are the same object.
if (Object.ReferenceEquals(x, y)) return true;
//Check whether the products' properties are equal.
return x != null && y != null && x.Code.Equals(y.Code) && x.Name.Equals(y.Name);
}
public int GetHashCode(ProductA obj)
{
//Get hash code for the Name field if it is not null.
int hashProductName = obj.Name == null ? 0 : obj.Name.GetHashCode();
//Get hash code for the Code field.
int hashProductCode = obj.Code.GetHashCode();
//Calculate the hash code for the product.
return hashProductName ^ hashProductCode;
}
}
ProductA[] store1 = { new ProductA { Name = "apple", Code = 9 },
new ProductA { Name = "orange", Code = 4 } };
ProductA[] store2 = { new ProductA { Name = "apple", Code = 9 },
new ProductA { Name = "lemon", Code = 12 } };
//Get the products from the both arrays
//excluding duplicates.
IEnumerable<ProductA> union =
store1.Union(store2);
foreach (var product in union)
Console.WriteLine(product.Name + " " + product.Code);
/*
This code produces the following output:
apple 9
orange 4
lemon 12
*/
The two options I use are:
list1.AddRange(list2);
or
list1.Concat(list2);
However I noticed as I used that when using the AddRange method with a recursive function, that calls itself very often I got an SystemOutOfMemoryException because the maximum number of dimensions was reached.
(Message Google Translated)
The array dimensions exceeded the supported range.
Using Concat solved that issue.
I just wanted to test how Union works with the default comparer on overlapping collections of reference type objects.
My object is:
class MyInt
{
public int val;
public override string ToString()
{
return val.ToString();
}
}
My test code is:
MyInt[] myInts1 = new MyInt[10];
MyInt[] myInts2 = new MyInt[10];
int overlapFrom = 4;
Console.WriteLine("overlapFrom: {0}", overlapFrom);
Action<IEnumerable<MyInt>, string> printMyInts = (myInts, myIntsName) => Console.WriteLine("{2} ({0}): {1}", myInts.Count(), string.Join(" ", myInts), myIntsName);
for (int i = 0; i < myInts1.Length; i++)
myInts1[i] = new MyInt { val = i };
printMyInts(myInts1, nameof(myInts1));
int j = 0;
for (; j + overlapFrom < myInts1.Length; j++)
myInts2[j] = myInts1[j + overlapFrom];
for (; j < myInts2.Length; j++)
myInts2[j] = new MyInt { val = j + overlapFrom };
printMyInts(myInts2, nameof(myInts2));
IEnumerable<MyInt> myUnion = myInts1.Union(myInts2);
printMyInts(myUnion, nameof(myUnion));
for (int i = 0; i < myInts2.Length; i++)
myInts2[i].val += 10;
printMyInts(myInts2, nameof(myInts2));
printMyInts(myUnion, nameof(myUnion));
for (int i = 0; i < myInts1.Length; i++)
myInts1[i].val = i;
printMyInts(myInts1, nameof(myInts1));
printMyInts(myUnion, nameof(myUnion));
The output is:
overlapFrom: 4
myInts1 (10): 0 1 2 3 4 5 6 7 8 9
myInts2 (10): 4 5 6 7 8 9 10 11 12 13
myUnion (14): 0 1 2 3 4 5 6 7 8 9 10 11 12 13
myInts2 (10): 14 15 16 17 18 19 20 21 22 23
myUnion (14): 0 1 2 3 14 15 16 17 18 19 20 21 22 23
myInts1 (10): 0 1 2 3 4 5 6 7 8 9
myUnion (14): 0 1 2 3 4 5 6 7 8 9 20 21 22 23
So, everything works fine.