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How to get Index of IEnumerable SelectList?

I want index from ViewBag and if not possible then From selectedlist but can't get it.
ViewBag.Lst_Fetch_Record = new SelectList(list.OrderBy(ITEM_CD => ITEM_CD));
int index = ViewBag.Lst_Fetch_Record.IndexOf("I1");

Use this method :
ViewBag.Lst_Fetch_Record.Select((item, index) => new
{
...Your Code
}

Getting Index without using for loop
var result2 = new SelectList(list.OrderBy(ITEM_CD=> ITEM_CD)).ToList();
INT Index = result2.IndexOf(result2.Where(p => p.Text == a).FirstOrDefault());

This will give you an ordered list with indexes
List<string> selectListName = new List<String>();
selectListName.Add("Ohio");
selectListName.Add("Maine");
selectListName.Add("Texas");
selectListName.Add("Oregon");
selectListName.Add("Alabama");
var result2 = selectListName.Select( (state, index) => new { index, state
}).OrderBy(a=>a.state).ToList();
foreach(var b in result2)
{
Console.WriteLine( b.index + " " + b.state) ;
}
result: If you re looking for the existing index
4 Alabama
1 Maine
0 Ohio
3 Oregon
2 Texas
To use the result
Console.WriteLine(result2.FirstOrDefault(a=>a.state.Equals("Ohio")).index);
2
Console.WriteLine(result2.FirstOrDefault(a=>a.index.Equals(2)).state);
Ohio
To get this result:
0 Alabama
1 Maine
2 Ohio
3 Oregon
4 Texas
Order first, then index as shown below
var result2 = selectListName.OrderBy(a=>a).Select( (state, index) => new { index,
state }).ToList();
foreach(var b in result2)
{
Console.WriteLine( b.index + " " + b.state) ;
}

Check this example:
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
}
public static void OrderByEx1()
{
Pet[] pets = { new Pet { Name="Barley", Age=8 },
new Pet { Name="Boots", Age=4 },
new Pet { Name="Whiskers", Age=1 } };
IEnumerable<Pet> query = pets.OrderBy(pet => pet.Age);
foreach (Pet pet in query)
{
Console.WriteLine("{0} - {1}", pet.Name, pet.Age);
}
}
Source: Microsoft documentation
https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.orderby?view=net-5.0

Linq: find similar objects from two different lists

I've got two separate lists of custom objects. In these two separate lists, there may be some objects that are identical between the two lists, with the exception of one field ("id"). I'd like to know a smart way to query these two lists to find this overlap. I've attached some code to help clarify. Any suggestions would be appreciated.
namespace ConsoleApplication1
{
class userObj
{
public int id;
public DateTime BirthDate;
public string FirstName;
public string LastName;
}
class Program
{
static void Main(string[] args)
{
List<userObj> list1 = new List<userObj>();
list1.Add(new userObj()
{
BirthDate=DateTime.Parse("1/1/2000"),
FirstName="John",
LastName="Smith",
id=0
});
list1.Add(new userObj()
{
BirthDate = DateTime.Parse("2/2/2000"),
FirstName = "Jane",
LastName = "Doe",
id = 1
});
list1.Add(new userObj()
{
BirthDate = DateTime.Parse("3/3/2000"),
FirstName = "Sam",
LastName = "Smith",
id = 2
});
List<userObj> list2 = new List<userObj>();
list2.Add(new userObj()
{
BirthDate = DateTime.Parse("1/1/2000"),
FirstName = "John",
LastName = "Smith",
id = 3
});
list2.Add(new userObj()
{
BirthDate = DateTime.Parse("2/2/2000"),
FirstName = "Jane",
LastName = "Doe",
id = 4
});
List<int> similarObjectsFromTwoLists = null;
//Would like this equal to the overlap. It could be the IDs on either side that have a "buddy" on the other side: (3,4) or (0,1) in the above case.
}
}
}

I don't know why you want a List<int>, i assume this is what you want:
var intersectingUser = from l1 in list1
join l2 in list2
on new { l1.FirstName, l1.LastName, l1.BirthDate }
equals new { l2.FirstName, l2.LastName, l2.BirthDate }
select new { ID1 = l1.id, ID2 = l2.id };
foreach (var bothIDs in intersectingUser)
{
Console.WriteLine("ID in List1: {0} ID in List2: {1}",
bothIDs.ID1, bothIDs.ID2);
}
Output:
ID in List1: 0 ID in List2: 3
ID in List1: 1 ID in List2: 4

You can implement your own IEqualityComparer<T> for your userObj class and use that to run a comparison between the two lists. This will be the most performant approach.
public class NameAndBirthdayComparer : IEqualityComparer<userObj>
{
public bool Equals(userObj x, userObj y)
{
return x.FirstName == y.FirstName && x.LastName == y.LastName && x.BirthDate == y.BirthDate;
}
public int GetHashCode(userObj obj)
{
unchecked
{
var hash = (int)2166136261;
hash = hash * 16777619 ^ obj.FirstName.GetHashCode();
hash = hash * 16777619 ^ obj.LastName.GetHashCode();
hash = hash * 16777619 ^ obj.BirthDate.GetHashCode();
return hash;
}
}
}
You can use this comparer like this:
list1.Intersect(list2, new NameAndBirthdayComparer()).Select(obj => obj.id).ToList();

You could simply join the lists on those 3 properties:
var result = from l1 in list1
join l2 in list2
on new {l1.BirthDate, l1.FirstName, l1.LastName}
equals new {l2.BirthDate, l2.FirstName, l2.LastName}
select new
{
fname = l1.FirstName,
name = l1.LastName,
bday = l1.BirthDate
};
Instead of doing a simple join on just one property (column), two anonymous objects are created new { prop1, prop2, ..., propN}, on which the join is executed.
In your case we are taking all properties, except the Id, which you want to be ignored and voila:
Output:
And Tim beat me to it by a minute

var similarObjectsFromTwoLists = list1.Where(x =>
list2.Exists(y => y.BirthDate == x.BirthDate && y.FirstName == x.FirstName && y.LastName == x.LastName)
).ToList();
This is shorter, but for large list is more efficient "Intersect" or "Join":
var similarObjectsFromTwoLists =
list1.Join(list2, x => x.GetHashCode(), y => y.GetHashCode(), (x, y) => x).ToList();
(suposing GetHashCode() is defined for userObj)

var query = list1.Join (list2,
obj => new {FirstName=obj.FirstName,LastName=obj.LastName, BirthDate=obj.BirthDate},
innObj => new {FirstName=innObj.FirstName, LastName=innObj.LastName, BirthDate=innObj.BirthDate},
(obj, userObj) => (new {List1Id = obj.id, List2Id = userObj.id}));
foreach (var item in query)
{
Console.WriteLine(item.List1Id + " " + item.List2Id);
}

Filtering and grouping items in a .NET List<>

List<MailingList> myGroup = lst.GroupBy(t => new {t.userId, t.userName,t.email,t.reportTypeId})
.Select(g => new MailingList
{
userId = g.Key.userId,
Acrynom = g.SelectMany(t => t.Acrynom).ToArray(),
userName = g.Key.userName,
email = g.Key.email,
reportTypeId = g.Key.reportTypeId
}).ToList();
foreach (var mailingList in myGroup.Distinct())
{
StringBuilder AcrynomsList1 = new StringBuilder();
foreach (var item in mailingList.Acrynom)
{
if (Acrynoms.Length > 0)
{
Acrynoms.Append(", ");
}
AcrynomsList1.Append(item);
}
}
What i want to achieve is filter and group myGroup by reportTypeId. reportTypeId can either be 1 or 2, so i want to have a variable StringBuilder AcrynomsList1 where reportTypeId = 1 and then another variable StringBuilder AcrynomsList2 where reportTypeId = 2.
My current StringBuilder varibale AcrynomsList1 has all reportTypeId 1 & 2 values.

This should give you what you want:
var list = lst.GroupBy(x => x.reportTypeId)
.Select(x => new
{
reportTypeId = x.Key,
Acronyms = x.SelectMany(t => t.Acrynom).ToArray()
}).ToList();
var acronymList1 = string.Join(", ", list[0].Acronyms);
var acronymList2 = string.Join(", ", list[1].Acronyms);

You can group it straight into a string without using a StringBuilder:
class Program
{
static void Main(string[] args)
{
var list = new List<MailingList>();
var grouped = list
.GroupBy(m => m.ReportTypeID)
.Select(g => new
{
ReportTypeID = g.Key,
Items = string.Join(", ", g.Where(s => !string.IsNullOrEmpty(s.Acronym)).Select(m => m.Acronym))
});
}
}
class MailingList
{
public int ReportTypeID { get; set; }
public string Acronym { get; set; }
}
The GroupBy extension method returns a number of enumerables of MailingList for you, which has a Key to expose the key you grouped by. The Distinct is part of the GroupBy, so you don't need it.

query to get all action during for each hour

i want to run and print a query that shows the number of orders per each hour in a day(24).
should look like:
hour-1:00, number of orders-5
hour-2:00, number of orders-45
hour-3:00, number of orders-25
hour-4:00, number of orders-3
hour-5:00, number of orders-43
and so on...
i try:
public void ShowBestHours()
{
using (NorthwindDataContext db = new NorthwindDataContext())
{
var query =
from z in db.Orders
select new Stime
{
HourTime = db.Orders.GroupBy(x => x.OrderDate.Value.Hour).Count(),
};
foreach (var item in query)
{
Console.WriteLine("Hour : {0},Order(s) Number : {1}", item.HourTime, item.Count);
}
}
}
public class Stime
{
public int HourTime { get; set; }
public int Count { get; set; }
}

You need to change your query to
var query =
from z in db.Orders
group z by z.OrderDate.Value.Hour into g
select new Stime{ HourTime = g.Key, Count=g.Count () };
or alternatively
var query = db,Orders.GroupBy (o => o.OrderDate.Value.Hour).Select (
g => new Stime{ HourTime=g.Key, Count=g.Count () });
In my copy of Northwind all of the OrderDate values are dates only so the result is just
HourTime = 0, Count = 830.
I'm assuming you're just experimenting with grouping. Try grouping by day of week like this
var query = db.Orders.GroupBy (o => o.OrderDate.Value.DayOfWeek).Select (
g => new { DayOfWeek=g.Key, Count=g.Count () });
which gives a more useful result.

You aren't setting Stime.Count anywhere in your query and you aren't grouping by hour correctly. I haven't seen your exact setup of course, but I think the following should work for you.
var query =
from z in db.Orders
group z by z.OrderDate.Value.Hour into g
select new Stime() { HourTime = g.Key, Count = g.Count() };
foreach (var item in query)
{
Console.WriteLine("Hour : {0},Order(s) Number : {1}", item.HourTime, item.Count);
}

Try this:
public void ShowBestHours()
{
using (NorthwindDataContext db = new NorthwindDataContext())
{
var query = db.Orders.GroupBy(x => x.OrderDate.Value.Hour).OrderByDescending(x => x.Count()).Select(x => new Stime { HourTime = x.Key, Count = x.Count() });
foreach (var item in query)
{
Console.WriteLine("Hour : {0},Order(s) Number : {1}", item.HourTime, item.Count);
}
}
}

Can a single LINQ Query Expression be framed in this scenario?

I am facing a scenario where I have to filter a single object based on many objects.
For sake of example, I have a Grocery object which comprises of both Fruit and Vegetable properties. Then I have the individual Fruit and Vegetable objects.
My objective is this:
var groceryList = from grocery in Grocery.ToList()
from fruit in Fruit.ToList()
from veggie in Vegetable.ToList()
where (grocery.fruitId = fruit.fruitId)
where (grocery.vegId = veggie.vegId)
select (grocery);
The problem I am facing is when Fruit and Vegetable objects are empty.
By empty, I mean their list count is 0 and I want to apply the filter only if the filter list is populated.
I am also NOT able to use something like since objects are null:
var groceryList = from grocery in Grocery.ToList()
from fruit in Fruit.ToList()
from veggie in Vegetable.ToList()
where (grocery.fruitId = fruit.fruitId || fruit.fruitId == String.Empty)
where (grocery.vegId = veggie.vegId || veggie.vegId == String.Empty)
select (grocery);
So, I intend to check for Fruit and Vegetable list count...and filter them as separate expressions on successively filtered Grocery objects.
But is there a way to still get the list in case of null objects in a single query expression?

I think the LINQ GroupJoin operator will help you here. It's similar to the TSQL LEFT OUTER JOIN

IEnumerable<Grocery> query = Grocery
if (Fruit != null)
{
query = query.Where(grocery =>
Fruit.Any(fruit => fruit.FruitId == grocery.FruitId));
}
if (Vegetable != null)
{
query = query.Where(grocery =>
Vegetable.Any(veggie => veggie.VegetableId == grocery.VegetableId));
}
List<Grocery> results = query.ToList();

Try something like the following:
var joined = grocery.Join(fruit, g => g.fruitId,
f => f.fruitId,
(g, f) => new Grocery() { /*set grocery properties*/ }).
Join(veggie, g => g.vegId,
v => v.vegId,
(g, v) => new Grocery() { /*set grocery properties*/ });
Where I have said set grocery properties you can set the properties of the grocery object from the g, f, v variables of the selector. Of interest will obviouly be setting g.fruitId = f.fruitId and g.vegeId = v.vegeId.

var groceryList =
from grocery in Grocery.ToList()
join fruit in Fruit.ToList()
on grocery.fruidId equals fruit.fruitId
into groceryFruits
join veggie in Vegetable.ToList()
on grocery.vegId equals veggie.vegId
into groceryVeggies
where ... // filter as needed
select new
{
Grocery = grocery,
GroceryFruits = groceryFruits,
GroceryVeggies = groceryVeggies
};

You have to use leftouter join (like TSQL) for this. below the query for the trick
private void test()
{
var grocery = new List<groceryy>() { new groceryy { fruitId = 1, vegid = 1, name = "s" }, new groceryy { fruitId = 2, vegid = 2, name = "a" }, new groceryy { fruitId = 3, vegid = 3, name = "h" } };
var fruit = new List<fruitt>() { new fruitt { fruitId = 1, fname = "s" }, new fruitt { fruitId = 2, fname = "a" } };
var veggie = new List<veggiee>() { new veggiee { vegid = 1, vname = "s" }, new veggiee { vegid = 2, vname = "a" } };
//var fruit= new List<fruitt>();
//var veggie = new List<veggiee>();
var result = from g in grocery
join f in fruit on g.fruitId equals f.fruitId into tempFruit
join v in veggie on g.vegid equals v.vegid into tempVegg
from joinedFruit in tempFruit.DefaultIfEmpty()
from joinedVegg in tempVegg.DefaultIfEmpty()
select new { g.fruitId, g.vegid, fname = ((joinedFruit == null) ? string.Empty : joinedFruit.fname), vname = ((joinedVegg == null) ? string.Empty : joinedVegg.vname) };
foreach (var outt in result)
Console.WriteLine(outt.fruitId + " " + outt.vegid + " " + outt.fname + " " + outt.vname);
}
public class groceryy
{
public int fruitId;
public int vegid;
public string name;
}
public class fruitt
{
public int fruitId;
public string fname;
}
public class veggiee
{
public int vegid;
public string vname;
}
EDIT:
this is the sample result
1 1 s s
2 2 a a
3 3