LINQ ToDictionary() Method

In LINQ, the ToDictionary operator is useful to convert list/collection (IEnumerable<T>) items to a new dictionary object (Dictionary<TKey, TValue>), and it will optimize the list/collection items by getting only required values.

Syntax of LINQ ToDictionary Operator

Following is the syntax of using the LINQ ToDictionary operator to convert the collection to a new dictionary object.

LINQ ToDictionary Syntax in C#

var student = objStudent.ToDictionary(x => x.Id, x => x.Name);

LINQ ToDictionary Syntax in VB.NET

Dim student = objStudent.ToDictionary(Function(x) x.Id, Function(x) x.Name)

If you observe the above syntax, we convert the “objStudent” collection to a dictionary object and get only the required field values (Id and Name).

LINQ ToDictionary Operator Example

Following is the example of using the LINQ ToDictionary operator to convert the collection to a new dictionary object.

C# Code

using System;
 using System.Linq;
 using System.Collections.Generic;

 namespace LINQExamples
 {
  class Program
  {
    static void Main(string[] args)
    {
      List<Student> objStudent = new List<Student>()
      {
        new Student() { Id=1,Name = "Suresh Dasari", Gender = "Male",Location="Chennai" },
        new Student() { Id=2,Name = "Rohini Alavala", Gender = "Female", Location="Chennai" },
        new Student() { Id=3,Name = "Praveen Alavala", Gender = "Male",Location="Bangalore" },
        new Student() { Id=4,Name = "Sateesh Alavala", Gender = "Male", Location ="Vizag"},
        new Student() { Id=5,Name = "Madhav Sai", Gender = "Male", Location="Nagpur"}
      };
      var student = objStudent.ToDictionary(x => x.Id, x => x.Name);
      foreach (var stud in student)
      {
        Console.WriteLine(stud.Key + "\t" + stud.Value);
      }
      Console.ReadLine();
    }
  }
  class Student
  {
    public int Id { get; set; }
    public string Name { get; set; }
    public string Gender { get; set; }
    public string Location { get; set; }
  }
 }

VB.NET Code

Module Module1

 Sub Main()
 Dim objStudent As New List(Of Student)() From {
 New Student() With {.Id = 1, .Name = "Suresh Dasari", .Gender = "Male", .Location = "Chennai"},
 New Student() With {.Id = 2, .Name = "Rohini Alavala", .Gender = "Female", .Location = "Chennai"},
 New Student() With {.Id = 3, .Name = "Praveen Alavala", .Gender = "Male", .Location = "Bangalore"},
 New Student() With {.Id = 4, .Name = "Sateesh Alavala", .Gender = "Male", .Location = "Vizag"},
 New Student() With {.Id = 5, .Name = "Madhav Sai", .Gender = "Male", .Location = "Nagpur"}
 }
 Dim student = objStudent.ToDictionary(Function(x) x.Id, Function(x) x.Name)
 For Each stud In student
 Console.WriteLine(Convert.ToString(stud.Key) + vbTab + stud.Value)
 Next
 Console.ReadLine()
 End Sub

 Class Student
 Public Property Id() As Int32
 Get
 Return m_Id
 End Get
 Set(ByVal value As Int32)
 m_Id = value
 End Set
 End Property
 Private m_Id As Int32
 Public Property Name() As String
 Get
 Return m_Name
 End Get
 Set(ByVal value As String)
 m_Name = value
 End Set
 End Property
 Private m_Name As String
 Public Property Gender() As String
 Get
 Return m_Gender
 End Get
 Set(ByVal value As String)
 m_Gender = value
 End Set
 End Property
 Private m_Gender As String
 Public Property Location() As String
 Get
 Return m_Location
 End Get
 Set(ByVal value As String)
 m_Location = value
 End Set
 End Property
 Private m_Location As String
 End Class
 End Module

If you observe the above example, we are converting the “objStudent” collection to dictionary object and getting values from two fields (Id and Name)

Result of LINQ ToDictionary Operator Example

Following is the result of the LINQ ToDictionary operator example.

1       Suresh Dasari
 2       Rohini Alavala
 3       Praveen Alavala
 4       Sateesh Alavala
 5       Madhav Sai