string[] arr= new string[]{"Anish","Jeeba","Jiya"};
- IEnumerable<string> obj= (from item in arr select $"{item} is my name").ToList();
using let
var result=from a in arr
let name= a.StartsWith('a')
where name
select a;
List<List<SampleList>> sam=new List<List<SampleList>>{
new List<SampleList>
{
new List<SampleList>
{
new SampleList{Name="Anish", number=31, Gender="M"},
new SampleList{Name="Anish", number=61, Gender="M"}
},
new List<SampleList>
{
new SampleList{Name="Jeeba", number=12, Gender="F"},
new SampleList{Name="Jiya", number=44, Gender="F"}
},
new List<SampleList>
{
new SampleList{Name="libu", number=12, Gender="M"},
new SampleList{Name="Vipin", number=55, Gender="F"}
}
};
var x= (from s in sam
let val=s
from v in val
where v.number > 32
select new SampleList{
Name= v.Name,
number= v.number,
}).ToList();
List<List<int>> li=new List<List<int>>{
new List<int>{1,2,3},
new List<int>{6,7,8},
};
var res= from l in li
from z in l
let square=z*z
where square > 50
select z;
Group By
var res = from s in sam
from x in s
// where x.number > 18 Conditions can also be added
group x by x.Gender;
foreach (var item in res)
{
Console.WriteLine($"{item.Key}");
foreach (var i in item)
Console.WriteLine($" {i.Name} : {i.number}");
}
OR
var output = res.Select(i => new
{
key = i.Key,
data = i.Select(z => new SampleList { Gender = z.Gender, Name = z.Name, number = z.number }).ToList()
});
foreach (var item in output)
{
Console.WriteLine($"Lambda: {item.key}");
foreach (var i in item.data)
Console.WriteLine($" {i.Name} : {i.number}");
}
Since we have grouped the data based on gender. So gender becomes the Key and the data is present in the inner loop.
First Letter of the Name Group
var alphabetGroup = from s in sam
from x in s
group x by x.Name[0];
By Multiple Keys
We group the data based on gender and numbervar multipleKeys = from s in sam
from x in s
group x by new { x.Gender, x.number };
If we need to further order our data, we will need to create another query (as the query needs to end in a group by or select statement) and order the data accordingly. But we can use the into keyword to perform this operation in the same query.
INTO
var multInto = from s in sam
from x in s
group x by new { x.number, x.Gender } into newGroup
orderby newGroup.Key.number
select $"{newGroup.Key.Gender}: {newGroup.Count()} ";
Group based on a key that does not exist (Usage of let)
Group based on age in the list given below. Such that numbers less than 18 fall under category "kid", > 18 "Boy" and > 50 "Old". We cannot use if else , but we can use the ternary operations.
List<int> ageList = new List<int> { 1, 2, 3, 44, 55, 66, 77, 88 };
var res = from age in ageList
let x = age > 18 ?
(age > 50) ? "Old" : "Boy"
: "kid"
group age by x into sample
select new {
key=sample.Key,
count=sample.Count(),
data=sample
};
foreach (var item in res)
{
Console.WriteLine($"{item.key}: {item.count}");
foreach (var i in item.data)
{
Console.WriteLine($" {i}");
}
}
List<List<SampleList>> sam = new List<List<SampleList>>{
new List<SampleList>
{
new SampleList{Name="Anish", number=31, Gender="M"},
new SampleList{Name="Anish", number=61, Gender="M"}
},
new List<SampleList>
{
new SampleList{Name="Jeeba", number=12, Gender="F"},
new SampleList{Name="Jiya", number=44, Gender="F"}
},
new List<SampleList>
{
new SampleList{Name="libu", number=31, Gender="M"},
new SampleList{Name="Vipin", number=55, Gender="F"}
},
};
List<List<SampleList2>> sam1 = new List<List<SampleList2>>{
new List<SampleList2>
{
new SampleList2{Name1="abc", number1=31, Gender1="M"},
new SampleList2{Name1="xyz", number1=62, Gender1="M"}
},
new List<SampleList2>
{
new SampleList2{Name1="fff", number1=12, Gender1="F"},
new SampleList2{Name1="Jiya", number1=45, Gender1="F"}
},
new List<SampleList2>
{
new SampleList2{Name1="eee", number1=24, Gender1="M"},
new SampleList2{Name1="vvv", number1=55, Gender1="F"}
},
};
Getting Inner data using SelectMany
var s2 = sam.SelectMany(i => i.Select(z => new SampleList
{ number = z.number, Gender = z.Gender, Name = z.Name })).ToList();
Left Join
For every item in s2 , check if we have an entry. group matching records in s1 and if no records exist then display "no name available"
var res1 = (from sIn in s1
join sin2 in s2 on sIn.number1 equals sin2.number into g
select new
{
sss = g.DefaultIfEmpty(new SampleList() {
Name="No Name",
Gender="NA",
number=0
}).ToList(),
NameS=sIn.Name1,
NumS=sIn.number1
}).ToList();
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