I have a c# object:
var obj = new Item { xcoords="1,2,3", ycoords="5,6,7", zcoords="8,9,4" }
So I want to split this into an array like following:
[
new Item2 { x=1, y=5, z=8 },
new Item2 { x=2, y=6, z=9 },
new Item2 { x=3, y=7, z=4 }
]
Can I do this using Linq? or another way in c#?
Let's create a helper method (either as separate method or as local function):
static IEnumerable<int> ToInts(string s) => s.Split(',').Select(p => Int32.Parse(p));
Putting things together:
var obj = new Item { xcoords = "1,2,3", ycoords = "5,6,7", zcoords = "8,9,4" };
var result = ToInts(obj.xcoords)
.Zip(ToInts(obj.ycoords), ToInts(obj.zcoords))
.Select(t => new Item2{ x = t.First, y = t.Second, z = t.Third });
Note: this overload of Zip (since .NET 6?, the doc is wrong on this point) produces tuples with 3 elements named First, Second and Third.
You can append a .ToArray() if you need an array of Coord.
Test assuming that ToString is overridden like this in Item2:
public override string ToString() => $"[{x}, {y}, {z}]";
foreach (var item in result) {
Console.WriteLine(item);
}
yields:
[1, 5, 8]
[2, 6, 9]
[3, 7, 4]
You don't need LINQ here if coords number is static.
var obj = new Item { xcoords="1,2,3", ycoords="5,6,7", zcoords="8,9,4" };
var xcoords = obj.xcoords.Split(',');
var ycoords = obj.ycoords.Split(',');
var zcoords = obj.zcoords.Split(',');
var result = new Item2[]
{
new Item2 { x = int.Parse(xcoords[0]), y = int.Parse(ycoords[0]), z = int.Parse(zcoords[0]) },
new Item2 { x = int.Parse(xcoords[1]), y = int.Parse(ycoords[1]), z = int.Parse(zcoords[1]) },
new Item2 { x = int.Parse(xcoords[2]), y = int.Parse(ycoords[2]), z = int.Parse(zcoords[2]) },
};
If coords number is dynamic but same for x, y and z then simple "for" loop may resolve the problem.
var obj = new Item { xcoords="1,2,3,4", ycoords="5,6,7,8", zcoords="8,9,4,10" };
var xcoords = obj.xcoords.Split(',');
var ycoords = obj.ycoords.Split(',');
var zcoords = obj.zcoords.Split(',');
var result = new Item2[xcoords.Length];
for (var i = 0; i < xcoords.Length; i++)
{
result[i] = new Item2
{
x = int.Parse(xcoords[i]),
y = int.Parse(ycoords[i]),
z = int.Parse(zcoords[i])
};
}
LINQ version (Requires .NET 6 or higher. In the previous versions Zip method takes only 2 collections at once.):
var obj = new Item { xcoords = "1,2,3,4", ycoords = "5,6,7,8", zcoords = "8,9,4,10" };
var result = Enumerable
.Zip(
obj.xcoords.Split(','),
obj.ycoords.Split(','),
obj.zcoords.Split(','),
(x, y, z) => (x, y, z))
.Select(
coord => new Item2
{
x = int.Parse(coord.x),
y = int.Parse(coord.y),
z = int.Parse(coord.z)
});
Linq approach https://dotnetfiddle.net/CHizmw
Item obj = new Item { xcoords = "1,2,3", ycoords = "5,6,7", zcoords = "8,9,4" };
Func<string, int[]> GetInt = value => value.Split(',').Select(int.Parse).ToArray();
var helper = new { xc = GetInt(obj.xcoords), yc = GetInt(obj.ycoords), zc = GetInt(obj.zcoords) };
Item2[] obj2 = Enumerable.Range(0, helper.xc.Length).Select(o => new Item2() { x = helper.xc[o], y = helper.yc[o], z = helper.zc[o] }).ToArray();
Related
I have a big list of objects and in this object there is a category ID something like:
var list = new List<Example>
{
new Example {CatId = 1, Value = new { }},
new Example {CatId = 1, Value = new { }},
new Example {CatId = 1, Value = new { }},
new Example {CatId = 2, Value = new { }},
new Example {CatId = 2, Value = new { }},
new Example {CatId = 3, Value = new { }}
// and so on
};
So I am looking for making this complicated list more organized like list of lists of unique elements
something like:
var result = new List<List<Example>>
{
new List<Example>
{
new Example {CatId = 1, Value = new { }},
new Example {CatId = 2, Value = new { }},
new Example {CatId = 3, Value = new { }}
},
new List<Example>
{
new Example {CatId = 1, Value = new { }},
new Example {CatId = 2, Value = new { }}
},
new List<Example>
{
new Example {CatId = 1, Value = new { }}
}
}
Problem is I do not what to use, group by will not fix my case, so how to do this in most efficient way.
So this is about partitioning, it's the sort of thing that is easy to do in a database query, but in c# you need to create some key with a partition number that you can then use to .GroupBy.
The partitioning itself is a grouping
var projected = list.GroupBy(x => x.CatId)
.SelectMany( g => g.Select( ( x, i ) => new { Item = x, rn = i + 1 } ) );
This gives you records that look like:
{"Item":{"CatId":1,"Value":{}},"rn":1}
{"Item":{"CatId":1,"Value":{}},"rn":2}
{"Item":{"CatId":1,"Value":{}},"rn":3}
{"Item":{"CatId":2,"Value":{}},"rn":1}
{"Item":{"CatId":2,"Value":{}},"rn":2}
{"Item":{"CatId":3,"Value":{}},"rn":1}
As you can see that rn ("row number") value can be used to group by:
var result = projected.GroupBy(x => x.rn, x => x.Item);
This gives us:
[{"CatId":1,"Value":{}},{"CatId":2,"Value":{}},{"CatId":3,"Value":{}}]
[{"CatId":1,"Value":{}},{"CatId":2,"Value":{}}]
[{"CatId":1,"Value":{}}]
So, all in 1 go:
var result = list.GroupBy(x => x.CatId)
.SelectMany( g => g.Select( ( x, i ) => new { Item = x, rn = i + 1 } ) )
.GroupBy(x => x.rn, x => x.Item);
Live example: https://dotnetfiddle.net/AlTfk8
I'm facing an issue while displaying multiple lists the value in a single row column.
Here is an example of code.
public class Program
{
static void Main(string[] args)
{
Dictionary<string, List<object>> keyvalues = new Dictionary<string, List<object>>();
keyvalues.Add("Code", new List<object>() { 1, 2, 3, 4 });
keyvalues.Add("Name", new List<object>() { "A", "B", "C", "D" });
keyvalues.Add("Age", new List<object>() { 20, 30, 40, 50 });
var listData = keyvalues.Select(x => x.Value).Select((x, i) => new { obj = x, index = i });
var listData = keyvalues.Select((x, iparent) => x.Value.Select((z, i) => new { value = string.Concat(z, x.Value[i]) }).ToList()).ToList();
Console.ReadLine();
}
}
Expected output
1A20
2B30
3C40
4D50
If you are using .Net 6, you could make use of the new 3 way Zip extension.
var result = keyvalues["Code"].Zip(keyvalues["Name"], keyvalues["Age"])
.Select(x=> $"{x.First}{x.Second}{x.Third}");
Why make it so complicated?
for(int x = 0; x<keyValues["Code"].Count; x++)
Console.WriteLine(
keyValues["Code"][x]+
keyValues["Name"][x]+
keyValues["Age"][x]
);
LINQ's a hammer; not every problem is a nail.
ps if you have N keys, you can easily turn it into a
var keys = new[]{"Code","Name","Age","Foo","Bar"};
for(...)
foreach(var k in keys)
... //some concat here or use the values directly eg adding to your page
You could easily use Zip here. However, you could roll your own
public static IEnumerable<string> DoStuff<T, T2>(Dictionary<T, List<T2>> source)
{
var max = source.Values.Max(x => x?.Count ?? 0);
for (var i = 0; i < max; i++)
yield return string.Concat(source.Values.Select(x => x.ElementAtOrDefault(i)));
}
Usage
var results = DoStuff(keyvalues);
Console.WriteLine(string.Join(Environment.NewLine,results));
Output
1A20
2B30
3C40
4D50
or
public static IEnumerable<string> DoStuff<T>(List<T>[] source)
{
var max = source.Max(x => x?.Count ?? 0);
for (var i = 0; i < max; i++)
yield return string.Concat(source.Select(x => x.ElementAtOrDefault(i)));
}
...
var results = DoStuff(keyvalues.Values.ToArray());
Console.WriteLine(string.Join(Environment.NewLine,results));
Here's a list, think of it as rows and columns where rows are going down and columns are side ways. the column count will always be the same for all rows.
var dataValues = new List<List<string>>()
{
//row 1
new List<string>(){"A","12","X","P8" },
//row 2
new List<string>(){"B","13","Y","P7" },
//row 3
new List<string>(){"C","12","Y","P6" },
//row 4
new List<string>(){"A","14","X","P5" },
//....
new List<string>(){"D","15","Z","P4" },
new List<string>(){"A","13","X","P3" },
new List<string>(){"B","14","Y","P2" },
new List<string>(){"C","13","Z","P1" },
};
The user providers a list of indexes to group by.
var userParam= new List<int>() { 0, 2 };
my question is how do i dynamically group dataValues by the userParam where user param is n amount of index. In the example above it will gorup by the first column and the 3rd. However the index can change and the amount of indexes can change aswell
example
var userParam2 = new List<int>() { 0, 2};
var userParam3 = new List<int>() { 0};
var userParam4 = new List<int>() { 0,1,2};
i know how to group by when i know how many indexes there will be (the the case below it's 2 index parameters), however when it's dynamic (x amount) then i do not know how to do this
var result = dataValues.GroupBy(e => new { G1 = e[userParam2 [0]], G2 = e[userParam2 [1]] });
You could use a Custom Comparer to achieve this :
1 - Declaration of GroupByComparer that inherit from IEqualityComparer :
public class GroupByComparer : IEqualityComparer<List<string>>
{
private static List<int> _intList;
public GroupByComparer(List<int> intList)
{
_intList = intList;
}
public bool Equals(List<string> x, List<string> y)
{
foreach (int item in _intList)
{
if (x[item] != y[item])
return false;
}
return true;
}
public int GetHashCode(List<string> obj)
{
int hashCode = 0;
foreach (int item in _intList)
{
hashCode ^= obj[item].GetHashCode() + item;
}
return hashCode;
}
}
2 - Call group by with EqualityComparer like :
var userParam = new List<int>() { 0, 2 };
var result = dataValues.GroupBy(e => e, new GroupByComparer(userParam));
I hope you find this helpful.
I believe i have something but this looks slow please let me know if there is anyway better of doing this.
var userParams = new List<int>() { 0, 2 };
var dataValues = new List<List<string>>()
{
new List<string>(){"A","12","X","P8" },
new List<string>(){"B","13","Y","P7" },
new List<string>(){"C","12","Y","P6" },
new List<string>(){"A","14","X","P5" },
new List<string>(){"D","15","Z","P4" },
new List<string>(){"A","13","X","P3" },
new List<string>(){"B","14","Y","P2" },
new List<string>(){"C","13","Z","P1" },
};
var result = new List<(List<string> Key, List<List<string>> Values)>();
result.Add((new List<string>(), dataValues));
for (int index = 0; index < userParams.Count; index++)
{
var currentResult = new List<(List<string> Key, List<List<string>> Values)>();
foreach (var item in result)
{
foreach (var newGroup in item.Values.GroupBy(e => e[userParams[index]]))
{
var newKey = item.Key.ToList();
newKey.Add(newGroup.Key);
currentResult.Add((newKey, newGroup.ToList()));
}
}
result = currentResult;
}
foreach(var res in result)
{
Console.WriteLine($"Key: {string.Join(#"\", res.Key)}, Values: {string.Join(" | ", res.Values.Select(e=> string.Join(",",e)))}");
}
final result
Key: A\X, Values: A,12,X,P8 | A,14,X,P5 | A,13,X,P3
Key: B\Y, Values: B,13,Y,P7 | B,14,Y,P2
Key: C\Y, Values: C,12,Y,P6
Key: C\Z, Values: C,13,Z,P1
Key: D\Z, Values: D,15,Z,P4
This question already has answers here:
LINQ - Full Outer Join
(16 answers)
Closed 4 years ago.
Here I have 2 lists of same object type.
object = {id: xxx, ...} // attribute "id" is used to find the identical obj
List oldSet = [old1, old2, old3];
List newSet = [new2, new3, new4];
// old2 = {id= 2, result = 5, ...}
// new2 = {id= 2, result = 1, ...}
// expected result = {oldSet: old2; newSet: new2}
I want to merge both lists, also keeping the origin of which list it came from.
The expected result as below:
List mergedSet = [{old1, null}, {old2, new2}, {old3, new3}, {null, new4}];
I'm thinking to use LINQ C# for it, but stuck somewhere.
Kindly advise.
Thanks! :)
Here's some code that does what you want using Linq. It basically walks through all the old list, and adds pairs to the merged list by looking for matches from the new list (and adding null as the second item if no match was found). Then it walks through the remaining items in the new list and adds them with null for the first item. It selects a dynamic type with two properties: OldSet and NewSet, so you know where each item came from.
The merge code is simply:
var mergedSet = oldSet.Select(o =>
new {OldSet = o, NewSet = newSet.FirstOrDefault(n => n.id == o.id)})
.Concat(newSet.Where(n => oldSet.All(o => o.id != n.id)).Select(n =>
new {OldSet = (Item) null, NewSet = n}));
This is based on the following item class:
class Item
{
public int id { get; set; }
public string result { get; set; }
public override string ToString()
{
return $"{result}{id}";
}
}
We create our lists:
List<Item> oldSet = new List<Item>
{
new Item {id = 1, result = "old"},
new Item {id = 2, result = "old"},
new Item {id = 3, result = "old"},
};
List<Item> newSet = new List<Item>
{
new Item {id = 2, result = "new"},
new Item {id = 3, result = "new"},
new Item {id = 4, result = "new"},
};
Run the merge code (very first snippet), and then display results:
foreach (var item in mergedSet)
{
Console.WriteLine($"{item.NewSet},{item.OldSet}");
}
Output
Try something like this :
List<string> oldSet = new List<string>() {"old1", "old2", "old3"};
List<string> newSet = new List<string>() {"new2", "new3", "new4"};
var results = oldSet.Select((x,i) => new { oldSet = x, newSet = newSet[i]}).ToList();
You can left join the two lists. I edited the answer as you actually need to left join twice, union, and apply a select distinct to get the cases where oldSet = null and no duplicates...
var mergedSet = (from o in oldSet
join n in newSet on o.id equals n.id into ns
from n in ns.DefaultIfEmpty()
select new { OldSet = o, NewSet = n })
.Union(from n in newSet
join o in oldSet on n.id equals o.id into os
from o in os.DefaultIfEmpty()
select new { OldSet = o, NewSet = n })
.Distinct();
Might be an overkill, but if you really want to use LINQ
List<Item> oldSet = new List<Item>
{
new Item {id = 1, result = "old"},
new Item {id = 2, result = "old"},
new Item {id = 3, result = "old"},
};
List<Item> newSet = new List<Item>
{
new Item {id = 2, result = "new"},
new Item {id = 3, result = "new"},
new Item {id = 4, result = "new"},
};
var resultL = oldSet.GroupJoin(
newSet,
o => o.id,
n => n.id,
(o,n) => new { Old = o, New = n })
.SelectMany(
n => n.New.DefaultIfEmpty(),
(o,n) => new Tuple<Item,Item>(o.Old,n));
var resultR= newSet.GroupJoin(
oldSet,
n => n.id,
o=> o.id,
(n,o) => new { Old = o, New = n })
.SelectMany(
o=> o.Old.DefaultIfEmpty(),
(n,o) => new Tuple<Item,Item>(o,n.New));
var result = resultL.Union(resultR).Distinct();
In this case, you have to use two GroupJoin and the Union the results.
Look at the following code:
var res1 = oldSet.GroupJoin(newSet, o => o, k => k, (x, y) => { var yy = y.FirstOrDefault(); return new { X = x, Y = yy }; });
var res2 = newSet.GroupJoin(oldSet, o => o, k => k, (x, y) => { var yy = y.FirstOrDefault(); return new { X = yy, Y = x }; });
var result = res1.Union(res2).ToList();// Your result is here
I have these two classes in my code and a List of Class2. I want to group the list elements by date and ID using LINQ.
public class Class1
{
public string ID;
public int y;
public int z;
}
public class Class2
{
public List<Class1> a;
public int p, q;
public string s;
public DateTime date;
}
My list is similar to this:
List<Class2> object1 = new List<Class2>
{
new Class2 {p = 5, q = 6, date = DateTime.Now, a = new List<Class1> { new Class1 { ID = "3643746HDJ", y = 0, z = 9 }, new Class1 { ID = "746327846HDJ", y = 0, z = 9 } } },
new Class2 {p = 5, q = 6, date = DateTime.Now.AddDays(1), a = new List<Class1> { new Class1 { ID = "3643746HDJ", y = 0, z = 9 }, new Class1 { ID = "746327846HDJ", y = 0, z = 9 } } },
new Class2 {p = 5, q = 6, date = DateTime.Now.AddDays(2), a = new List<Class1> { new Class1 { ID = "3643746HDJ", y = 0, z = 9 }, new Class1 { ID = "746327846HDJ", y = 0, z = 9 } } },
new Class2 {p = 5, q = 6, date = DateTime.Now.AddDays(3), a = new List<Class1> { new Class1 { ID = "3643746HDJ", y = 0, z = 9 }, new Class1 { ID = "746327846HDJ", y = 0, z = 9 } } },
};
Sorry if this is a stupid question, but I am a beginner in C# programming and LINQ and I am not sure if this is even possible.
This is what I have tried based on examples I saw on the web but its not correct
var newList = from item in object1
group new
{
item.s,
item.a[0].x, //I think its wrong because of this
item.a[0].y //and this
}
by new
{
item.date,
item.a[0].ID //and this
}
into temp
select temp;
Since I have hardcoded index 0 in the grouping I am missing a lot of elements in my final list. How can I do this for all elements of list a in Class2?
Expected output is similar to this:
Key: {date: 19-09-2017 ID: 3643746HDJ}, Element: {{s: "abc", y = 1, z = 2}, {s: "pqr", y = 2, z = 4}, {s: "abc", y = 1, z = 2}}
Key: {date: 20-09-2017 ID: 3643746HDJ}, Element: {{s: "pop", y = 1, z = 2}, {s: "dfr", y = 2, z = 4}, {s: "abc", y = 1, z = 2}}
Key: {date: 19-09-2017 ID: 746327846HDJ}, Element: {{s: "abc", y = 7, z = 8}, {s: "asar", y = 2, z = 111}, {s: "abc", y = 1, z = 2}}
Key: {date: 20-09-2017 ID: 746327846HDJ}, Element: {{s: "abc", y = 7, z = 8}, {s: "asar", y = 2, z = 111}, {s: "abc", y = 1, z = 2}}
Your question states:
Since I have hardcoded index 0 in the grouping I am missing a lot of elements in my final list. How can I do this for all elements of list a in Class2?
As you want all the items from the nested collections you need to flatten the nested collections before grouping. In query syntax do so using another from:
var result = from item in object1
from nested in item.a
group new { item.s, nested.y, nested.z } by new { item.date, nested.ID } into g
select g;
As each nested object does not have a p and q properties but your code shows accessing the nested items I used y and z instead
This can also be done using method syntax. To flatten the nested collections use SelectMany. For the GroupBy you can use the overload where you specify both key and element selector. General idea for that:
var result = object1.SelectMany(item => item.a.Select(nested => new {item, nested }))
.GroupBy(key => new { key.item.Date, key.nested.Id },
val => new { val.item.s, val.nested.x, val.nestd.y });
Even though it seems it is only for question purposes only I recommend giving meaningful names for properties and variables and to have a look at:
MSDN Naming Conventions
Dofactory