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c# cross join two same type of lists

So here I have some code, which works ok. But I want to change the select part to something else, I am not sure what other methods I can use any help would be appreciated.
using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
var all = new List<People>{new People{Id = 1, Name = "andy1", Age = null}, new People{Id = 2, Name = "andy2", Age = null}, new People{Id = 3, Name = "andy3", Age = null}, new People{Id = 4, Name = "andy4", Age = null}, };
var someOfThem = new List<People>{new People{Id = 1, Name = null, Age = 1}, new People{Id = 2, Name = null, Age = 1},new People{Id = 3, Name = null, Age = 1}};
var test = someOfThem.Select(c =>
{
c.Name = all.Find(a => a.Id == c.Id).Name;
return c;
});
foreach (var item in test)
Console.WriteLine("{0}={1}={2}", item.Id, item.Name, item.Age);
}
}
public class People
{
public int Id
{
get;
set;
}
public int? Age
{
get;
set;
}
public string Name
{
get;
set;
}
}
And here is the result.
1=andy1=1
2=andy2=1
3=andy3=1
I am just wondering is there another way to achieve the same result but a more elegant way? or an easier way?
var test = someOfThem.Select(c =>
{
c.Name = all.Find(a => a.Id == c.Id).Name;
return c;
});
Update
Sorry I did not show my problem properly at first, I have updated my quesiton. Please have a look again.

You can use C#'s LINQ keywords and more specifically, the join keyword assosciated with it:
using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
var all = new List<People> { new People { Id = 1, Name = "andy1", }, new People { Id = 2, Name = "andy2", }, new People { Id = 3, Name = "andy3", }, new People { Id = 4, Name = "andy4", }, };
var someOfThem = new List<People> { new People { Id = 1, Name = null, }, new People { Id = 2, Name = null, } };
var test = from item in someOfThem
join element in all on item.Id equals element.Id
select element;
foreach (var item in test)
Console.WriteLine("{0}={1}", item.Id, item.Name);
}
}
public class People
{
public int Id
{
get;
set;
}
public string Name
{
get;
set;
}
}
The code version would be
var test = someOfThem.Join(all, item => item.Id, element => element.Id, (item, element) => element);
as shown in Robert's comment

You can use the Join (you can also use a dictionary, but I'm not going to show it):
Here's the syntax for join:
var test = someOfThem.Join(all, item => item.Id, element => element.Id,
(item, element) => new Person {
Id = item.Id ?? element.Id,
Name = item.Name ?? element.Name,
Age = item.Age ?? element.Age
});

You can implement Equals and GetHashCode in your People class and use Intersect.
Or, create an EqualityComparer, that way your comparison logic is decoupled:
class Program
{
public static void Main()
{
var all = new List<People> { new People { Id = 1, Name = "andy1", }, new People { Id = 2, Name = "andy2", }, new People { Id = 3, Name = "andy3", }, new People { Id = 4, Name = "andy4", }, };
var someOfThem = new List<People> { new People { Id = 1, Name = null, }, new People { Id = 2, Name = null, } };
var test = all.Intersect(someOfThem, new PeopleIdComparer()).ToList();
foreach (var item in test)
Console.WriteLine("{0}={1}", item.Id, item.Name);
}
}
public class PeopleIdComparer : IEqualityComparer<People>
{
public bool Equals(People x, People y)
{
return x.Id == y.Id;
}
public int GetHashCode(People obj)
{
return HashCode.Combine(obj.Id);
}
}
public class People
{
public int Id
{
get;
set;
}
public string Name
{
get;
set;
}
}

How to merge two different List

I have a List<string> list1, example values:
var list1 = new List<string>()
{
"123", "1234", "12345",
};
I have a class:
public class TestClass {
public string name{ get; set; }
public int count{ get; set; }
}
and I have a List<TestClass> list2, example values:
var list2 = new List<TestClass>()
{
new TestClass() { name = "12", count = 0 },
new TestClass() { name = "123", count = 5 },
new TestClass() { name = "1234", count = 20 },
};
I want to merge list1 and list2 and the result should be:
name count
12 0
123 5
1234 20
12345 0

This works nicely:
var list1 = new List<string>()
{
"123", "1234", "12345",
};
var list2 = new List<TestClass>()
{
new TestClass() { name = "12", count = 0 },
new TestClass() { name = "123", count = 5 },
new TestClass() { name = "1234", count = 20 },
};
var merged =
list2
.Concat(list1.Select(x => new TestClass() { name = x, count = 0 }))
.GroupBy(x => x.name)
.SelectMany(x => x.Take(1))
.ToList();
It gives me:

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
List<TestClass> lst1 = new List<TestClass>();
lst1.Add(new TestClass(){name="One", count = 1});
lst1.Add(new TestClass(){name="Two", count = 2});
lst1.Add(new TestClass(){name="Three", count = 3});
List<TestClass> lst2 = new List<TestClass>();
lst2.Add(new TestClass(){name="Four", count = 4});
lst2.Add(new TestClass(){name="Two", count = 2});
lst2.Add(new TestClass(){name="Three", count = 3});
var unionlst = lst1.Union(lst2, new TestClassComparer ());
foreach(var x in unionlst){
Console.WriteLine(x.name + ","+x.count);
}
}
class TestClassComparer : IEqualityComparer<TestClass>
{
public bool Equals(TestClass p1, TestClass p2)
{
return p1.name == p2.name && p1.count == p2.count;
}
public int GetHashCode(TestClass p)
{
return p.count;
}
}
public class TestClass {
public string name{ get; set; }
public int count{ get; set; }
}
}
Sample output:
One,1
Two,2
Three,3
Four,4

Set PredicateBuilder also on child collection

I am trying to apply the predicate not only to the entity parent but also to the child collection. The following is part of my code:
var predicate = PredicateBuilder.New<Entity>();
foreach (string keyword in keywords)
{
string temp = keyword;
predicate = predicate.Or(p => p.Name.Equals(temp));
predicate = predicate.Or(p => p.Addresses.Select(x=> x.Name.Equals(temp));
}
The line predicate = predicate.Or(p => p.Addresses.Select(x=> x.Name.Equals(temp)); is not working ? any ideas as to why?
EDIT
In the following demo I am asking to get entity parent and child with name = tom but I also get child name = tom2.
private static void Main(string[] args)
{
var result = GetAll(GetAll(), new List<string> { "tom" });
}
private static List<User> GetAll()
{
return new List<User>
{
new User
{
Id = 1,
Name = "tom",
Addesses = new List<Addesses>
{
new Addesses { Id = 1, Name = "tom" },
new Addesses { Id = 1, Name = "tom2" },
}
},
new User
{
Id = 1,
Name = "sam",
Addesses = new List<Addesses>
{
new Addesses { Id = 1, Name = "sam" },
new Addesses { Id = 1, Name = "sam2" },
}
},
};
}
private static List<User> GetAll(List<User> users, List<string> keywords)
{
var predicate = PredicateBuilder.New<User>();
foreach (string keyword in keywords)
{
string temp = keyword;
predicate = predicate.Or(p => p.Name.Equals(temp));
predicate = predicate.Or(p => p.Addesses.Any(x => x.Name.Equals(temp)));
}
var result = users
.Where(predicate)
.ToList();
return result;
}
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public List<Addesses> Addesses { get; set; }
}
public class Addesses
{
public int Id { get; set; }
public string Name { get; set; }
}

The call to p.Addresses.Select(x=> x.Name.Equals(temp) is not returning a boolean result.
Depending on your actual logic you may want to look into Any:
predicate = predicate.Or(p => p.Addresses.Any(x=> x.Name.Equals(temp));
or All:
predicate = predicate.Or(p => p.Addresses.All(x=> x.Name.Equals(temp));

Code review of this portion of Linq Filters

I am a newbie of c #, I would like to know if I can remove the for each and do a single operation with Linq. I would like to return an IEnumerable with already filtered. is it possible to do this? Every suggestion is welcome, thank you very much
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Linq
{
class Oggetto
{
public int Id { get; set; }
public string MyProperty { get; set; }
public int Deleted { get; set; }
}
class Program
{
static void Main(string[] args)
{
IEnumerable<Oggetto> lista = new List<Oggetto> {
new Oggetto(){ Id = 1, MyProperty = "Propr1", Deleted = 0 },
new Oggetto(){ Id = 1, MyProperty = "Propr2", Deleted = 1 },
new Oggetto(){ Id = 2, MyProperty = "Prop3", Deleted = 0 },
new Oggetto(){ Id = 3, MyProperty = "Propr4", Deleted = 0 },
new Oggetto(){ Id = 3, MyProperty = "Prop5", Deleted = 1 }
};
foreach (var item in lista.Where(x => x.Deleted == 1).GroupBy(x => x.Id).Select(g => g.First()))
{
item.MyProperty = string.Join(",", lista.Where(t => t.Id == item.Id).Select(x => x.MyProperty).ToArray());
Console.WriteLine(item.Id);
Console.WriteLine(item.MyProperty);
}
Console.ReadLine();
}
}
}

You can use projection for this.
var orderedList = lista.GroupBy(x => x.Id)
.Where(x => x.Any(y => y.Deleted == 1))
.Select(x => new Oggetto
{
Id = x.Key, MyProperty = string.Join(",", x.Select(v => v.MyProperty))
});
foreach (var item in orderedList)
{
Console.WriteLine(item.Id);
Console.WriteLine(item.MyProperty);
}
Anyway, as #Alex said you shoud replace Deleted field type to bool and as said by #Marco Salerno start programming in English you'll not regret.

First of all I would avoid the groupBy statement. This is a lot of unneded overhead. You can use distinct instead. This will give you all the IDs you need to know.
var ids = lista.Where(x => x.Deleted).Select(x => x.Id).Distinct();
You can then select all the elements that you need with:
var items = ids.Select(i => lista.Where(x => x.Id == i));
which results in a List of Lists. For the ease of use I would convert this to a Dictionary<K, V> (int this case it's Dictionary<long, List<string>> as a final step:
var dictionary = items.ToDictionary(l => l.First().Id, l => l.Select(o => o.MyProperty).ToList());
You now got a "nice and filtered" collection you can use any way you like (or just output it)
foreach (var item in dictionary)
{
Console.WriteLine($"Id: {item.Key}");
Console.WriteLine($"Properties: {string.Join(", ", item.Value)}");
}
I also changed your class a little bit to:
class Oggetto
{
public int Id { get; set; }
public string MyProperty { get; set; }
// bool instead of int - Deleted has only 2 states
public bool Deleted { get; set; }
}

First of all STOP programming in Italian, start doing it in English.
Anyway, this should be a better approach:
class Program
{
static void Main(string[] args)
{
List<Item> items = new List<Item> {
new Item{ Id = 1, MyProperty = "Propr1", Deleted = 0 },
new Item{ Id = 1, MyProperty = "Propr2", Deleted = 1 },
new Item{ Id = 2, MyProperty = "Prop3", Deleted = 0 },
new Item{ Id = 3, MyProperty = "Propr4", Deleted = 0 },
new Item{ Id = 3, MyProperty = "Prop5", Deleted = 1}
};
foreach (IGrouping<int,Item> group in items.GroupBy(x => x.Id).ToList())
{
List<Item> groupItems = group.ToList();
Item deletedItem = groupItems.Where(x => x.Deleted == 1).FirstOrDefault();
if(deletedItem != null)
{
deletedItem.MyProperty = string.Join(",", groupItems.Select(x => x.MyProperty).ToArray());
Console.WriteLine(deletedItem.Id);
Console.WriteLine(deletedItem.MyProperty);
}
}
}
}
class Item
{
public int Id { get; set; }
public string MyProperty { get; set; }
public int Deleted { get; set; }
}

How can I sort a list that has potential parents with the parent objects first in the list?

In C#, if I have a list of objects, where each object can have a parent, and each parent can have a parent (x combinations), how is the best way to sort the list so that all the parent objects are first in the list?
Here is the object structure:
class test
{
int id { get; set; }
int parentId { get; set; }
bool hasParentObject { get; set; }
}
Here is an example of some objects:
Object a:
id = 1;
parentId = 0;
hasParentObject = false;
Object b:
id = 2;
parentId = 1;
hasParentObject = true;
Object c:
id = 3;
parentId = 2;
hasParentObject = true;
Thanks.
EDIT
With the following code, how can the code be modified so that if an object does not have a parent, the object is in the list before any objects that do have parents?
Code:
class Test : IComparable<Test>
{
public int Id { get; set; }
public int ParentId { get; set; }
public bool HasParentObject { get; set; }
public int CompareTo(Test other)
{
if(!this.HasParentObject)
return 1;
else if(!other.HasParentObject)
return 1;
else if(other.HasParentObject && this.HasParentObject)
return ParentId.CompareTo(other.ParentId);
else if(other.HasParentObject)
return 1;
else
return -1;
}
}

It sounds like you would want the objects that are parents first in the list (Optional: Ordered by ID), then you want the objects that aren't parents to follow the parent objects in the list (Optional: Ordered by ID).
This isn't a one liner, but I think it does what you're asking
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
{
List<Test> tests = new List<Test>
{
new Test() { Id = 6, ParentId = 2, HasParentObject = true },
new Test() { Id = 2, ParentId = 0, HasParentObject = false },
new Test() { Id = 1, ParentId = 0, HasParentObject = true },
new Test() { Id = 4, ParentId = 1, HasParentObject = true }
};
// Get the parents sorted
List<Test> sortedTests = tests.Where(t => tests.FindIndex(t2 => t2.ParentId == t.Id) != -1)
.OrderBy(t => t.Id)
.ToList();
// Add those that aren't parents sorted
sortedTests.AddRange(tests.Where(t => tests.FindIndex(t2 => t2.ParentId == t.Id) == -1)
.OrderBy(t => t.Id));
sortedTests.ForEach(t => Console.WriteLine("ID: {0} ParentId: {1}", t.Id, t.ParentId));
}
}
class Test
{
public int Id { get; set; }
public int ParentId { get; set; }
public bool HasParentObject { get; set; }
}
Results:
ID: 1 ParentId: 0
ID: 2 ParentId: 0
ID: 4 ParentId: 1
ID: 6 ParentId: 2
Fiddle Demo

You could implement the IComparable itherface for your class and then use the Sort method of the list.
class Test : IComparable<Test>
{
public int Id { get; set; }
public int ParentId { get; set; }
public bool HasParentObject { get; set; }
public int CompareTo(Test other)
{
if(other.HasParentObject && this.HasParentObject)
return ParentId.CompareTo(other.ParentId);
else if(other.HasParentObject)
return 1;
else
return -1;
}
}
Please look here for a working example based on your post's data.

if one can assume the hasParentObject property is public
public List<test> l;
public List<test> sortList(List<test> _l)
{
return _l.OrderByDescending(a => a.hasParentObject).ToList();
}

You can use new Comparison overload of Sort method - .Sort(new Comparison<test>(expression))
For instance :
List<test> list = new List<test>()
{
new test() { id=1, hasParentObject = false, parentId = 0 },
new test() { id=2, hasParentObject = true, parentId = 1 },
new test() { id=3, hasParentObject = false, parentId = 0 },
new test() { id=4, hasParentObject = true, parentId = 3 },
};
list.Sort((s1, s2) => s1.parentId > s2.parentId ? 1 : (s1.parentId < s2.parentId ? -1 : 0));
foreach (var item in list)
Console.WriteLine(item.id);
Console.ReadKey();