Let Vs Into Keywords in LINQ

Let Vs Into Keywords in LINQ

This article shows two keywords of LINQ. These keywords are very helpful when working with a set of object collections using LINQ.

First I will go through the Into keyword and its use.

I used the following collection in this article, on which I've done actions in this article.

  1: List<Mobile> objMobileCollection = new List<Mobile>  
  2: {   
  3: new Mobile{Provider="Apple",ModelName="IPhone3",ModelNumber="I100",MemoryCard=4},  
  4: new Mobile{Provider="Apple",ModelName="IPhone4",ModelNumber="I101",MemoryCard=8},  
  5: new Mobile{Provider="Apple",ModelName="IPhone4S",ModelNumber="I102",MemoryCard=16},  
  6: new Mobile{Provider="Apple",ModelName="IPhone5",ModelNumber="I103",MemoryCard=32},  
  7: new Mobile{Provider="Samsung",ModelName="GalaxyS",ModelNumber="S001",MemoryCard=4},  
  8: new Mobile{Provider="Samsung",ModelName="GalaxyS2",ModelNumber="S002",MemoryCard=16},  
  9: new Mobile{Provider="Samsung",ModelName="GalaxyS3",ModelNumber="S003",MemoryCard=20},  
 10: new Mobile{Provider="Samsung",ModelName="Grand",ModelNumber="G001",MemoryCard=4},  
 11: new Mobile{Provider="Nokia",ModelName="LUMIA530",ModelNumber="N1",MemoryCard=8},  
 12: new Mobile{Provider="Nokia",ModelName="LUMIA730",ModelNumber="N2",MemoryCard=16},  
 13: new Mobile{Provider="Nokia",ModelName="LUMIA930",ModelNumber="N3",MemoryCard=20},  
 14: };  

Into keyword
The Into keyword allows creating a temporary variable to store the results of a group, join or select clause into a new variable.

  1: var resultSet = from mobile in objMobileCollection  
  2: group mobile by new { mobile.Provider } into mGroup  
  3: orderby mGroup.Key.Provider  
  4: select new
  5: {  
  6: Provider = mGroup.Key.Provider,  
  7: ModelName = mGroup.OrderBy(x => x.ModelName),  
  8: //ModelNumber = mGroup.OrderBy(x => x.ModelNumber),
  9: //MemoryCard = mGroup.OrderBy(x => x.MemoryCard),
 10: };  
 11: 

In the above query after applying Into on mobile groping it creates the type mGroup variable to apply the next filter or create a temporary variable “mGroup” for further operations.

As in the code below:

  1: foreach (var items in resultSet)  
  2: {  
  3: Console.WriteLine("{0} - {1}", items.Provider, items.ModelName.Count());  
  4: Console.WriteLine("------------------------------------------------");  
  5: foreach (var item in items.ModelName)  
  6: {  
  7: Console.WriteLine(item.Provider + "\t" + item.ModelName + "\t\t" + item.ModelNumber.Trim() + "\t" + item.MemoryCard);  
  8: }  
  9: Console.WriteLine();  
 10: }  
 11: Console.ReadLine();  
 12: 

Please have a look at the output as shown in the following image:

Let Keyword


The Let keyword permits you to store the result of the query that can be used further in subsequent queries.
It creates a new variable and initializes it with the result of the expression and can be used further in queries just the opposite of the Into keyword, which means you created a new variable and you also can use the previous variable so you can use both in the further operations.

  1: var resultSetLet = (from mobile in objMobileCollection  
  2: group mobile by new { mobile.Provider } into mGroup  
  3: //orderby mGroup.Key.Provider,mGroup.Key.MemoryCard
  4: let avgMemory = mGroup.Sum(x => x.MemoryCard) / mGroup.Count()  
  5: where avgMemory > 11  
  6: select new
  7: {  
  8: Provider = mGroup.GroupBy(x => x.Provider),  
  9: ModelName = mGroup.OrderBy(m => m.ModelName),  
 10: ModelNumber = mGroup.OrderBy(x => x.ModelNumber)  
 11: //MemoryCard = mGroup.OrderBy(x => x.MemoryCard),
 12: }).ToList();  
 13: 

Kindly refer to the image shown below for further reference:

Please have a look at the complete code shown below:

  1: var resultSetLet = (from mobile in objMobileCollection  
  2: group mobile by new { mobile.Provider } into mGroup  
  3: //orderby mGroup.Key.Provider,mGroup.Key.MemoryCard
  4: let avgMemory = mGroup.Sum(x => x.MemoryCard) / mGroup.Count()  
  5: where avgMemory > 11  
  6: select new
  7: {  
  8: Provider = mGroup.GroupBy(x => x.Provider),  
  9: ModelName = mGroup.OrderBy(m => m.ModelName),  
 10: ModelNumber = mGroup.OrderBy(x => x.ModelNumber)  
 11: //MemoryCard = mGroup.OrderBy(x => x.MemoryCard),
 12: }).ToList();  
 13: 
 14: foreach (var items in resultSetLet)  
 15: {  
 16: Console.WriteLine("{0} - {1}", items.Provider, items.ModelNumber.Count());  
 17: Console.WriteLine("------------------------------------------------");  
 18: foreach (var item in items.ModelNumber)  
 19: {  
 20: Console.WriteLine(item.Provider + "\t" + item.ModelName + "\t\t" + item.ModelNumber + "\t" + item.MemoryCard);  
 21: }  
 22: Console.WriteLine();  
 23: }  
 24: Console.ReadLine();  

 
Please have a look at the output as shown below in the image:





Note: Group by multiple columns in LINQ to SQL as shown in the image below:




This is the complete code used in this article.

  1: using System;
  2: using System.Collections.Generic;
  3: using System.Linq;
  4: using System.Text;
  5: 
  6: namespace LINQ_LetKeyword
  7: {
  8:     #region hiddencode
  9:     //class Employee
 10:     //{
 11:     //    public string Name { get; set; }
 12:     //    public string EmpID { get; set; }
 13:     //    public int Salary { get; set; }
 14: 
 15:     //}
 16:     #endregion
 17: 
 18:     class Mobile
 19:     {
 20:         public string Provider { get; set; }
 21:         public string ModelName { get; set; }
 22:         public string ModelNumber { get; set; }
 23:         public int MemoryCard { get; set; }
 24:     }
 25: 
 26:     class Program
 27:     {
 28:         static void Main(string[] args)
 29:         {
 30: 
 31:             
 32: 
 33:             List<Mobile> objMobileCollection = new List<Mobile> { 
 34:              new Mobile{Provider="Apple",ModelName="IPhone3",ModelNumber="I100",MemoryCard=4},
 35:              new Mobile{Provider="Apple",ModelName="IPhone4",ModelNumber="I101",MemoryCard=8},
 36:              new Mobile{Provider="Apple",ModelName="IPhone4S",ModelNumber="I102",MemoryCard=16},
 37:              new Mobile{Provider="Apple",ModelName="IPhone5",ModelNumber="I103",MemoryCard=32},
 38:              new Mobile{Provider="Samsung",ModelName="GalaxyS",ModelNumber="S001",MemoryCard=4},
 39:              new Mobile{Provider="Samsung",ModelName="GalaxyS2",ModelNumber="S002",MemoryCard=16},
 40:              new Mobile{Provider="Samsung",ModelName="GalaxyS3",ModelNumber="S003",MemoryCard=20},
 41:              new Mobile{Provider="Samsung",ModelName="Grand",ModelNumber="G001",MemoryCard=4},
 42:              new Mobile{Provider="Nokia",ModelName="LUMIA530",ModelNumber="N1",MemoryCard=8},
 43:              new Mobile{Provider="Nokia",ModelName="LUMIA730",ModelNumber="N2",MemoryCard=16},
 44:              new Mobile{Provider="Nokia",ModelName="LUMIA930",ModelNumber="N3",MemoryCard=20},
 45: 
 46:             };
 47: 
 48: 
 49:             var resultSet = from mobile in objMobileCollection
 50:                             group mobile by new { mobile.Provider, mobile.MemoryCard } into mGroup
 51:                             orderby mGroup.Key.Provider
 52:                             select new
 53:                             {
 54:                                 Provider = mGroup.Key.Provider,
 55:                                 ModelName = mGroup.OrderBy(x => x.ModelName),
 56:                                 //ModelNumber = mGroup.OrderBy(x => x.ModelNumber),
 57:                                 //MemoryCard = mGroup.OrderBy(x => x.MemoryCard),
 58:                             };
 59: 
 60:             foreach (var items in resultSet)
 61:             {
 62:                 Console.WriteLine("{0} - {1}", items.Provider, items.ModelName.Count());
 63:                 Console.WriteLine("------------------------------------------------");
 64:                 foreach (var item in items.ModelName)
 65:                 {
 66:                     Console.WriteLine(item.Provider + "\t" + item.ModelName + "\t\t" + item.ModelNumber.Trim() + "\t" + item.MemoryCard);
 67:                 }
 68:                 Console.WriteLine();
 69:             }
 70:             Console.ReadLine();
 71: 
 72: 
 73:             /////////////Var Keyword uses
 74: 
 75: 
 76:             //var resultSetLet = (from mobile in objMobileCollection
 77:             //                    group mobile by new { mobile.Provider } into mGroup
 78:             //                    //orderby mGroup.Key.Provider,mGroup.Key.MemoryCard
 79:             //                    let avgMemory = mGroup.Sum(x => x.MemoryCard) / mGroup.Count()
 80:             //                    where avgMemory > 11
 81:             //                    select new
 82:             //                    {
 83:             //                        Provider = mGroup.GroupBy(x => x.Provider),
 84:             //                        ModelName = mGroup.OrderBy(m => m.ModelName),
 85:             //                        ModelNumber = mGroup.OrderBy(x => x.ModelNumber)
 86:             //                        //MemoryCard = mGroup.OrderBy(x => x.MemoryCard),
 87:             //                    }).ToList();
 88:             
 89:             //foreach (var items in resultSetLet)
 90:             //{
 91:             //    Console.WriteLine("{0} - {1}", items.Provider, items.ModelNumber.Count());
 92:             //    Console.WriteLine("------------------------------------------------");
 93:             //    foreach (var item in items.ModelNumber)
 94:             //    {
 95:             //        Console.WriteLine(item.Provider + "\t" + item.ModelName + "\t\t" + item.ModelNumber + "\t" + item.MemoryCard);
 96:             //    }
 97:             //    Console.WriteLine();
 98:             //}
 99:             //Console.ReadLine();
100:             //var objresult = from emp in objEmployee
101:             //                let totalSalary = objEmployee.Sum(sal => sal.Salary)
102:             //                let avgSalary = totalSalary / 5
103:             //                where avgSalary > emp.Salary
104:             //                select emp;
105: 
106:             
107:         }
108:     }
109: }
110: 

I wish it will help you utilize both features at the best.
To learn more about MVC please go to the following link.


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Thanks.
Enjoy coding and reading.

Categories: Entity Framework & LINQ