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I have searched for a few examples and not found one that is similar to what I have and what I want to achieve.
I have 2 lists
class object1
{
string obj1_name;
int obj1_qty;
}
List<object1> listA
class object2
{
string obj2_name;
int obj2_qty;
}
List<object2> listB;
Now, using ListA as the primary list I want to see if ListB contains an object with the same name and if so, what is the quantity and hence, does the obj1_qty = obj2_qty each other? if not, there is a difference and I need to show it, most likely in a 3rd list which would be the difference, of the qty's if they exist. Note, ListA can be bigger or smaller than ListB
Show All List A (master list contains all objects)
Show the difference between those names/qty's that exist in both lists.
Gracias
Souncs like a join would work for you:
var query = from a in listA
join b in listB on a.obj1_name equals b.obj2_name
where a.obj1_qty != b.obj2_qty
select new {
Name = a.obj1_name,
QtyA = a.obj1_qty,
QtyB = b.obj2_qty,
Diff = a.obj1_qty - b.obj2_qty
};
The simpelest way to do this is just use a join from Linq
var items = from l1 in listA
join l2tmp1 in listB on l1.obj1_name equals l2.obj2_name into l2tmp2
from l2 in l2tmp2.DefaultIfEmpty();
select new {
ItemA = l1,
ItemB = l2,
Name = l1.obj1_name,
Difference = (l2 == null) ? 0 : l1.ob1_qty - l2.ob2_qty
};
items will now hold a IEnumerable of a anonymous class that holds the a reference to the item in ListA, a reference to the item in listB, the matching name, and the difference.
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I have ExpesnseIDVM ViewModel that only contains 1 variable ExpenseID to hold the last value from the database
public IEnumerable<ExpesnseIDVM> Profile(LoginVM loginVM)
{
var data = (from a in context.Employees
where a.Email == loginVM.Email
join b in context.Expenses on a.EmployeeId equals b.EmployeeId
select new ExpesnseIDVM()
{ ExpenseID = b.ExpenseId }).ToList().LastOrDefault();
return data;
}
I have a problem with the return type, what type of return type should I use to get the values
Four problems here:
SQL Server do not guarantee order of the items if you do not specify OrderBy
SQL do not have LastOrDefault direct translation. EF may try to reverse defined OrderBy and call FirstOrDefault - again OrderBy required
LastOrDefault returns one instance, not enumerable
ToList() loads whole table into the memory, but you need just one record, so do not use it.
Consider to rewrite your query in the following way:
public ExpesnseIDVM Profile(LoginVM loginVM)
{
var data = (from a in context.Employees
where a.Email == loginVM.Email
join b in context.Expenses on a.EmployeeId equals b.EmployeeId
orderby b.ExpenseId descending
select new ExpesnseIDVM()
{ ExpenseID = b.ExpenseId }).FirstOrDefault();
return data;
}
You have IQueryable?<T> as return value of the linq query, then you have .ToList() That makes EF to calculate the query, getting List<T> and finally .LastOrDefault() that returns single object of T.
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Is there a better or more efficient way to do this?
Both of these objects have the same Id and some similar fields that I want to update.
foreach (var i in oldItems)
{
foreach (var j in newItemValues)
{
if(i.id == j.Id)
{
j.field1 = (decimal)i.field1;
j.field2 = (decimal)i.field2;
}
}
}
try this maybe you are like this;
foreach (var n in newItemValues)
{
Item item = oldItems.FirstOrDefault(x => x.Id == n.Id);
if (item != null)
{
n.field1 = item.field1;
n.field2 = item.field2;
}
}
Edit: If you keep oldItems in a HashSet or HashTable by keeping key as Id the time taken will slow to O(N).
Convert oldItems or newItemValues into a Map before looping.
That will reduce computational complexity from O(n^2) to O(n)
You can do this by Linq Query
newItemsValues =
(from t1 in oldItems
join t2 in newItemsValues on t1.Id equals t2.Id
select new YourModel { field1 = t1.field1 ,field2 = t1.field2 }
).ToList();
result will a list of all matching items where oldItems Id will be equals to newItemsValues Id
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I have 3 lists.
ListA<items>
ListB<items>
ListC<items>
I have to select one item from each list but the item.itemID should be unique for each of those items. How can i achieve this? Thanks in advance.
List<items> concat = new List<items>();
concat.AddRange(ListA);
concat.AddRange(ListB);
concat.AddRange(ListC);
List<items> result = new List<items>();
foreach (var item in concat)
{
if (result.Where(x => x.itemId == item.itemId).Count() == 0)
{
result.add(item);
}
}
//result should now contain what you are looking for
So you want exactly one item from each list, where that item hasn't been selected already from a previous list?
Then select from the lists where the ID isn't in the previous selection. Maybe something like this:
var itemA = listA.First(); // any item is unique, since this is our first one
var itemB = listB.First(b => b.ID != itemA.ID);
var itemC = listC.First(c => c.ID != itemA.ID && c.ID != itemB.ID);
If the count of lists isn't known then we'd need to make this a little more dynamic. Maybe something like this:
var selectedItems = new List<Item>();
foreach (var list in listOfLists)
selectedItems.Add(list.First(x => selectedItems.Count(y => y.ID == x.ID) == 0));
What this does is loop through the "list of lists" (since the number of lists isn't known, it must be in a collection data structure) and get the first item from each one where the currently known selected items do not have a matching ID. This should result in one selected item from each list.
(This all assumes that the lists contain a valid item that you're looking for. If that's not the case, you might use FirstOrDefault() instead and check for nulls.)
public class items
{
public int id {get;set;}
}
void Main()
{
var l1=new List<items>{new items {id=1}, new items {id=2}, new items {id=3}};
var l2=new List<items>{new items {id=2}, new items {id=3}, new items {id=4}};
var l3=new List<items>{new items {id=1}, new items {id=2}};
var result=l1
.Join(l2,(k1)=>true,(k2)=>true,(a1,a2)=>new {a1,a2})
.Join(l3,(k1)=>true,(k2)=>true,(b1,b2)=>new {b1.a1,b1.a2,a3=b2})
.Where(rec=>rec.a1.id!=rec.a2.id && rec.a2.id!=rec.a3.id && rec.a1.id!=rec.a3.id)
.First();
Console.WriteLine("{0},{1},{2}",result.a1.id,result.a2.id,result.a3.id);
}
Of the possible answers (132,142,231,241,321,341,342) it will pick and return the first one (132).
Example code: http://csharppad.com/gist/98a076bdd4e01dbd82be
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I have two tables, each one stored in a List.
The table has two columns (thus arrays in lists are of size two)
List<int[]> tablea;
List<int[]> tableb;
Content of tablea
a b
{1,2}
{3,4}
{5,6}
content of tableb
b c
{2,3}
{2,4}
{6,7}
Now I wish to join two tables by field b, hence the result is
a b c
{1,2,3}
{1,2,4}
{5,6,7}
I know I can do this is sort merge join algorithms, and the algorithms is quite intuitive.
But I heard hybrid hashjoin(mentioned here http://en.wikipedia.org/wiki/Hash_join#_note-1) is faster.
May I know how to use hybrid hashjoin algorithms to join tablea and tableb in C#(Preferably) or java?
(What I concern here is speed rather than space)
The ode that can handle non-unique key values, would be like this:
Dictionary<int, List<int[]>> hashA = new Dictionary<int, List<int[]>>();
foreach (int[] a in tablea) {
List<int> list;
if (!hashA.TryGetValue(a[1], out list) {
list = new List<int>();
hashA.Add(a[1], list);
}
list.Add(a);
}
List<int[]> result = new List<int[]>();
foreach (int[] b in tableb) {
List<int[]> a;
if (hashA.TryGetValue(b[0], out a) {
foreach (int[] line in a) {
result.Add(new int[] { line[0], line[1], b[1] });
}
}
}
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I have two list : (Note: List's Items are combination of "NAME" & "ID" )
List<string> ListA = new List() {"SAM001","SAM002","SAM003","PIT001","PIT002","PIT004","ROSE001","ROSE002","JASE001" };
//so on
List<string> ListB = new List() {"SAM001","SAM003","PIT000","ROSE002","JASE001","INDI000"};`
//so on...
Now Based on these two list i want to create two new list suppose listCommon & listUncommon.
listCommon will contain all matched items of ListA & ListB.
listUnCommon will contain all remaining items of ListA
Now My condition is if Any item in ListB has NAME + 000 then all the items of ListA starting with that Name should add in my listCommon.
Example 1 : if ListB item is PIT000 and ListA item are PIT001,PIT002,PIT003,ABC001
then listCommon = PIT001,PIT002,PIT003 because ListB has PIT with 000 so condition true all ListA 'PIT' items added in listcommon
So as above list and my condition i want my final list below
List<string> listCommon = new List() {"SAM001","SAM003", "PIT001","PIT002","PIT004","ROSE002", "JASE001" };
List<string> listUncommon = new List() {"SAM002", "ROSE001"};
Please suggest..i just spend my couple of minutes in loops but not getting actual result as i mentioned :(
This should work.
var common = ListA.Intersect(ListB)
.Concat(
ListA.Where(a =>
ListB.Any(
b => b.EndsWith("000") &&
b.StartsWith(a.Substring(0, a.Length - 3))
)
)
);
var uncommon = ListA.Except(common);
Using an insersect, then you are selecting any from list A where list B has an entry that matches the first 3 letters and ends with 000.
This is not the most efficient way of doing this, however it is terse code-wise.
Finding the common items from 2 lists:
var listCommon = list1.Intersect(list2);
Updated - Subtracted items:
var subtractedItems = new HashSet(listCommon);
commonItems.ExceptWith(list1);