Solved

# sort array list of structure (key value)

Posted on 2011-02-21
374 Views
I have an Array list of a custom class which is essentially has two attributes Key and Va
public class myClass
{
public key { get; set; }
public value { get; set; }
}

ArrayList myList = new ArrayList();
myList is a list of myClass

How can I sort myList by Key?

I've been doing this below in the past the problem is i can't use it anymore because it doesn't handle the case of duplicate keys, i cant have two of same keys in dictionary.
loop and add to dictionary (Key, Value)
Then sort dictionary
Dictionary<string, string> sortedTypes = myList .OrderBy(i => i.Key).ToDictionary(i => i.Key,
i => i.Value);
0
Question by:NewtonianB
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LVL 9

Assisted Solution

Stephan_Schrandt earned 50 total points
ID: 34948262
You can use a custom comparer. Here's a good article on that: http://devcity.net/articles/20/1/20020304.aspx
0

LVL 23

Accepted Solution

wdosanjos earned 350 total points
ID: 34948629
Does the following work for you?

``````public class MyClass
{
public string key { get; set; }
public string value { get; set; }
}

void Main()
{
List<MyClass> myList = new List<MyClass>();

myList.Add(new MyClass(){key="XYZ", value="Test 3"});
myList.Add(new MyClass(){key="ABC", value="Test 1"});
myList.Add(new MyClass(){key="DEF", value="Test 2"});
myList.Add(new MyClass(){key="ABC", value="Test 1"});

List<MyClass> orderedList = myList.OrderBy(i => i.key).ToList();

foreach (var item in orderedList)
{
Console.WriteLine("key={0}, value={1}", item.key, item.value);
}
}
``````

Output:
``````key=ABC, value=Test 1
key=ABC, value=Test 1
key=DEF, value=Test 2
key=XYZ, value=Test 3
``````
0

Author Comment

ID: 34948760
Hi wdosanjos:
The output is what I want but I won't be able to try it until tomorrow.
How does it work? How does it manage to sort by value also?
0

LVL 23

Assisted Solution

wdosanjos earned 350 total points
ID: 34948841
It uses the generic version of List (List<MyClass>), then it uses Linq Extensions to do the sorting (.OrderBy).

The sample only sorts by 'key', if you need to sort by 'value' also the statement should be:

List<MyClass> orderedList = myList.OrderBy(i => i.key).ThenBy(i => i.value).ToList();

More Linq samples: http://msdn.microsoft.com/en-us/vcsharp/aa336746.aspx

I hope this helps.
0

LVL 20

Expert Comment

ID: 34949032
SortedList?
0

LVL 13

Assisted Solution

Naman Goel earned 100 total points
ID: 34950016
Please refer to following code

here I am using MyObject in ArrayList and MyObjectComparer will be our comparer class.

0

LVL 13

Expert Comment

ID: 34950059
code is here:
``````using System.Linq;
using System;
using System.Globalization;
using System.Collections;

namespace ConsoleApplication
{
public class MyObject
{
public string Key { get; set; }
public object Value { get; set; }
}

public class MyObjectComparer : IComparer
{

public int Compare(object x, object y)
{
return String.Compare((x as MyObject).Key, (y as MyObject).Key,false);
}
}

class Program
{
static void Main(string[] args)
{

ArrayList arrayList = new ArrayList(
new MyObject[]{
new MyObject { Key = "a1", Value=  1234 },
new MyObject { Key = "a2", Value=  1234 },
new MyObject { Key = "a1", Value=  1234 },
new MyObject { Key = "aa1", Value=  1234 },
new MyObject { Key = "ab1", Value=  1234 }
}
);
arrayList.Sort(new MyObjectComparer());

}
}
}
``````
0

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