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Select all from one List, replace values that exist on another List

Few days ago I asked same question with SQL, but now it arises in C# code
Lets say we have this kind of class for holding different id/text pairs:
public class Text {
public int id { get; set; }
public string text { get; set; }
...
}
Now lets populate some data,
ListA gets a lot of data:
List<Text> ListA = new List<Text>{
new () {id = 1, text = "aaa1"},
new () {id = 2, text = "aaa2"},
new () {id = 3, text = "aaa3"},
new () {id = 4, text = "aaa4"},
new () {id = 5, text = "aaa5"},
new () {id = 6, text = "aaa6"},
};
And ListB gets just a little bit of data:
List<Text> ListB = new List<Text>{
new () {id = 4, text = "bbb4"},
new () {id = 5, text = "bbb5"},
};
And now what we are looking:
var result = ... // Some Linq or Lambda magic goes here
// and if we do:
foreach(var item in result){
Console.WriteLine(item.Id + " " + item.Text);
}
// Result will be:
1 : aaa1
2 : aaa2
3 : aaa3
4 : bbb4
5 : bbb5
6 : aaa6

You can try looking for id within ListB:
var result = ListA
.Select(a => ListB.FirstOrDefault(b => b.id == a.id) ?? a);
Here for each a within ListA we try to find corresponding by id (b.id == a.id) item within ListB. If no such item is found we just return ListA item: ?? item
In case of .Net 6 you can use overloaded .FirstOrDefault version (we can pass a as a default value):
var result = ListA
.Select(a => ListB.FirstOrDefault(b => a.id == b.id, a));

It might be more efficient to convert ListB to a Dictionary first:
var dictB = ListB.ToDictionary(x=> x.id)
Then you can write
var result = ListA.Select(x => dictB.TryGetValue(x.id, out var b) ? b : x)
UPD Rewrote taking comment suggestions into account

One option is to do an Union operation, by specifying an EqualityComparer. If the order is important, you can do an OrderBy operation at the end.
class TextIdComparer : EqualityComparer<Text> {
public override bool Equals(Text x, Text y) => x.id == y.id;
}
var result = ListB.Union(ListA, new TextIdComparer()).OrderBy(x => x.id)

Add two objects in the same list

I have a list of objects. Each object contains an ID and a value. There are several objects which have the same ID but different values. How would I go about adding the values together based on the matching ID? Additionally, how would I go about removing one entry after the addition is complete?
The object in question:
public class MyObject
{
public int ID { get; set; }
public int Value { get; set; }
}
Below is where I am getting the duplicate objects from a list of all objects. I'm simply getting all the duplicate IDs into a list of strings and then grabbing the entire duplicate object in the duplicateObjects list.
List<MyObject> myObjects = GetMyObjectsList();
List<string> duplicateIds = myObjects.GroupBy(x => x.ID)
.Where(group => group.Count() > 1)
.Select(group => group.Key).ToList();
List<MyObject> duplicateObjects = myObjects.Where(x => duplicateIds.Contains(x.ID)).ToList();
I'm stuck on the last steps which are adding the duplicate values and then removing one of the duplicates. How would I accomplish this with Linq?

Assume the list look like this
var list = new MyObject[]
{
new MyObject {ID = 1, Value = 2},
new MyObject {ID = 2, Value = 2},
new MyObject {ID = 1, Value = 3},
new MyObject {ID = 4, Value = 4},
new MyObject {ID = 2, Value = 4},
};
Then just select from list group by ID and sum value like this
var result = (from tm in list
group tm by tm.ID into Test
select new
{
ID = Test.Key,
Value = Test.Sum(x => x.Value)
});
Output
ID = 1, Value = 5
ID = 2, Value = 6
ID = 4, Value = 4
working fiddle here

I hope I understood your question correctly.As clarified in the comment,you want to "sum" all the values grouped by ID and then remove one of the duplicates. Please verify if the following is how you could like it to be behave.
var duplicates = myObjects.GroupBy(x => x.ID)
.Select(group => new { Group = group.Count() > 1 ? group.ToList().Take(group.Count()-1) : group.ToList(),Sum=group.Count()});
For Input
Output
If you need to exclude non-duplicates, then you would need to include an additional Where Condition
var duplicates = myObjects.GroupBy(x => x.ID)
.Where(x=>x.Count()>1)
.Select(group => new { Group = group.Count() > 1 ? group.ToList().Take(group.Count()-1) : group.ToList(),Sum=group.Count()});

Add duplicates together in List

First question :)
I have a List<Materiau> (where Materiau implements IComparable<Materiau>), and I would like to remove all duplicates and add them together
(if two Materiau is the same (using the comparator), merge it to the first and remove the second from the list)
A Materiau contains an ID and a quantity, when I merge two Materiau using += or +, it keeps the same ID, and the quantity is added
I cannot control the input of the list.
I would like something like this:
List<Materiau> materiaux = getList().mergeDuplicates();
Thank you for your time :)

Check out Linq! Specifically the GroupBy method.
I don't know how familiar you are with sql, but Linq lets you query collections similarly to how sql works.
It's a bit in depth to explain of you are totally unfamiliar, but Code Project has a wonderful example
To sum it up:
Imagine we have this
List<Product> prodList = new List<Product>
{
new Product
{
ID = 1,
Quantity = 1
},
new Product
{
ID = 2,
Quantity = 2
},
new Product
{
ID = 3,
Quantity = 7
},
new Product
{
ID = 4,
Quantity = 3
}
};
and we wanted to group all the duplicate products, and sum their quantities.
We can do this:
var groupedProducts = prodList.GroupBy(item => item.ID)
and then select the values out of the grouping, with the aggregates as needed
var results = groupedProducts.Select( i => new Product
{
ID = i.Key, // this is what we Grouped By above
Quantity = i.Sum(prod => prod.Quantity) // we want to sum up all the quantities in this grouping
});
and boom! we have a list of aggregated products

Lets say you have a class
class Foo
{
public int Id { get; set; }
public int Value { get; set; }
}
and a bunch of them inside a list
var foocollection = new List<Foo> {
new Foo { Id = 1, Value = 1, },
new Foo { Id = 2, Value = 1, },
new Foo { Id = 2, Value = 1, },
};
then you can group them and build the aggregate on each group
var foogrouped = foocollection
.GroupBy( f => f.Id )
.Select( g => new Foo { Id = g.Key, Value = g.Aggregate( 0, ( a, f ) => a + f.Value ) } )
.ToList();

List<Materiau> distinctList = getList().Distinct(EqualityComparer<Materiau>.Default).ToList();

How to return Distinct Row using LINQ

I have two rows which have all the data same except one column.
I want to show only one row on the UI but one row which has different data should be shown as comma seperated values.
Sample Data
PricingID Name Age Group
1 abc 56 P1
1 abc 56 P2
Output should be :
PricingID Name Age Group
1 abc 56 P1,P2
I am using this approach but it is not working , it gives me two rows only but data i am able to concatenate with comma.
List<PricingDetailExtended> pricingDetailExtendeds = _storedProcedures.GetPricingAssignment(pricingScenarioName, regionCode, productCode, stateCode, UserId, PricingId).ToList();
var pricngtemp = pricingDetailExtendeds.Select(e => new
{
PricingID = e.PricingID,
OpportunityID = e.OpportunityID,
ProductName = e.ProductName,
ProductCD = e.ProductCD
});
pricingDetailExtendeds.ForEach(e=>
{
e.ProductCD = string.Join(",",string.Join(",", (pricngtemp.ToList().Where(p => p.PricingID == e.PricingID).Select(k => k.ProductCD).ToArray())).Split(',').Distinct().ToArray());
e.OpportunityID =string.Join(",", string.Join(",", (pricngtemp.ToList().Where(p => p.PricingID == e.PricingID).Select(k => k.OpportunityID).ToArray())).Split(',').Distinct().ToArray());
e.ProductName =string.Join(",", string.Join(",", (pricngtemp.ToList().Where(p => p.PricingID == e.PricingID).Select(k => k.ProductName).ToArray())).Split(',').Distinct().ToArray());
}
);
// pricingDetailExtendeds = GetUniquePricingList(pricingDetailExtendeds);
return pricingDetailExtendeds.Distinct().AsEnumerable();
Any body can suggest me better approach and how to fix this issue ?
Any help is appreciated.

You want to use the GroupBy linq function.
I then use the String.Join function to make the groups comma seperated.
So something like this:
var pricingDetailExtendeds = new[]
{
new
{
PricingID = 1,
Name = "abc",
Age = 56,
Group = "P1"
},
new
{
PricingID = 1,
Name = "abc",
Age = 56,
Group = "P2"
}
};
var pricngtemp =
pricingDetailExtendeds.GroupBy(pde => new {pde.PricingID, pde.Name, pde.Age})
.Select(g => new {g.Key, TheGroups = String.Join(",", g.Select(s => s.Group))}).ToList();
You can easily extrapolate this to the other fields.
To return the PricingDetailExtended, the just create it in the select. So something like this
.Select(g => new PricingDetailExtended {
PricingID = g.Key.PricingId,
TheGroups = String.Join(",", g.Select(s => s.Group))
}).ToList();
You won't have the field TheGroups though, so just replace that field with the proper one.

An example of what I was describing in my comment would be something along the lines of the following. I would expect this to be moved into a helper function.
List<PriceDetail> list = new List<PriceDetail>
{
new PriceDetail {Id = 1, Age = 56, Name = "abc", group = "P1"},
new PriceDetail {Id = 1, Age = 56, Name = "abc", group = "P2"},
new PriceDetail {Id = 2, Age = 56, Name = "abc", group = "P1"}
};
Dictionary<PriceDetailKey, StringBuilder> group = new Dictionary<PriceDetailKey, StringBuilder>();
for (int i = 0; i < list.Count; ++i)
{
var key = new PriceDetailKey { Id = list[i].Id, Age = list[i].Age, Name = list[i].Name };
if (group.ContainsKey(key))
{
group[key].Append(",");
group[key].Append(list[i].group);
}
else
{
group[key] = new StringBuilder();
group[key].Append(list[i].group);
}
}
List<PriceDetail> retList = new List<PriceDetail>();
foreach (KeyValuePair<PriceDetailKey, StringBuilder> kvp in group)
{
retList.Add(new PriceDetail{Age = kvp.Key.Age, Id = kvp.Key.Id, Name = kvp.Key.Name, group = kvp.Value.ToString()});
}
you could even convert the final loop into a LINQ expression like:
group.Select(kvp => new PriceDetail {Age = kvp.Key.Age, Id = kvp.Key.Id, Name = kvp.Key.Name, group = kvp.Value.ToString()});
Its worth noting you could do something similar without the overhead of constructing new objects if, for example, you wrote a custom equality comparer and used a list instead of dictionary. The upside of that is that when you were finished, it would be your return value without having to do another iteration.
There are several different ways to get the results. You could even do the grouping in SQL.

Parse string and order by parsed value

i am trying to build linq expression to solve my problem. I have list of strings
List<string> arr = new List<string>();
arr.Add("<desc><ru>1</ru><en>3</en></desc>");
arr.Add("<desc><ru>2</ru><en>4</en></desc>");
i want to parse every item and order results
fake sample:
arr.Select(ParseItem("en")).OrderBy(x)
then we have two items in ru in order 1,2
Thanks for all and sorry for my bad English
Thanks for all response but how to convert now results to IQueryable
class Test { public string data { get; set; } }
List<Test> arr = new List<Test>();
arr.Add(new Test { data = "<desc><ru>AAA</ru><en>One</en></desc>" });
arr.Add(new Test { data = "<desc><ru>1</ru><en>Two</en></desc>" });
arr.Add(new Test { data = "<desc><ru>22</ru><en>Ab</en></desc>" });
IQueryable<Test> t = arr.AsQueryable();
// here the trouble how to convert to IQueryable<Test>
t = t.Select(s => XElement.Parse(s.data)).Select(x => x.Element("en")).
OrderBy(el => el.Value);
Thanks again

After the question update - this will return your ordered data by <en> node value:
var result = arr
.OrderBy(t=>
XElement.Parse(t.data).Element("en").Value
);
The result valiable is of IOrderedEnumerable<Test> type.

This will produce a list of the values in ru tags (assuming they are integers), ordered by the values in en tags (again, assuming integers).
List<string> items = arr.Select(s => XElement.Parse(s))
.OrderBy(xml => (int)xml.Element("en"))
.Select(xml => (int)xml.Element("ru"))
.ToList();
If you simply want to enumerate, you can omit the ToList call:
foreach (var item in arr.Select(s => XElement.Parse(s))
.OrderBy(xml => (int)xml.Element("en"))
.Select(xml => (int)xml.Element("ru")))
{
// do something with item
}

I'm not sure I've got what the excepted results are, but if you need to select values in en ordered by the value in ru then here it is:
var orderedItems = (
from item in arr
let x = XElement.Parse(item)
let ruValue = (int)x.Element("ru")
let enValue = (int)x.Element("en")
orderby ruValue
select enValue
).ToList();

I don't know if it is too late, but if you are wanting to parse the text and if it is an integer then sort by value otherwise sort by text, then this might help.
You need to define a function like this to enable parsing in LINQ expressions:
Func<string, int?> tryParseInteger = text =>
{
int? result = null;
int parsed;
if (int.TryParse(text, out parsed))
{
result = parsed;
}
return result;
};
Then you can do queries like this:
var xs = new [] { "Hello", "3ff", "4.5", "5", };
var rs =
(from x in xs
select tryParseInteger(x)).ToArray();
// rs == new int?[] { null, null, null, 5, };
In your case you possibly want something like this:
var elements = new []
{
"<desc><ru>AAA</ru></desc>",
"<desc><ru>1</ru></desc>",
"<desc><ru>42</ru></desc>",
"<desc><ru>-7</ru></desc>",
"<desc><ru>BBB</ru></desc>",
"<desc><ru>22</ru></desc>",
};
var query =
from e in elements
let xe = XElement.Parse(e)
let v = xe.Element("ru").Value
orderby v
orderby tryParseInteger(v)
select v;
Which would give you:
{ "AAA", "BBB", "-7", "1", "22", "42" }
If you want to treat non-integers (ie parsed as null) to be zero then change the query by using this line:
orderby tryParseInteger(v) ?? 0
Then you'll get this:
{ "-7", "AAA", "BBB", "1", "22", "42" }
I hope this helps.