Generic Collections - Some Common List(T) Operations using C# 2.0 and VB.NET
The List(T) represents a strongly typed collection of objects which is highly optimized for providing maximum performance and can be accessed using an index. This class provides methods to loop, filter, sort and manipulate collections. For those interested, the non-generic version of this class is the ArrayList class.
In this article we will see some common operations like search, sort, loop and manipulating lists. Since this article focuses on demonstrating some common operations of the Generics List(T) class, I have decided to keep the sample as simple as possible and will go ahead with a console application. I assume you are familiar with the features of C# 2.0 and VB.NET and understand Generics in particular. If not, you can read some new features of 2.0 and 3.0 over here.
To create a console application, open Visual Studio 2005/2008 > File > New Project > Select your desired Language and in the template pane, select Console application.
I will be using a collection of a ‘Person’ class and store it in the List(T). To add a Person class to your application, right click your project > Add > Class > rename the class to Person.cs or Person.vb. Add the following properties to the Person class:
C#
using System;
using System.Collections.Generic;
using System.Text;
namespace CommonGenericOperations
{
public class Person
{
public Person()
{
}
public Person(int id, string first_name, string mid_name, string last_name, short age, char sex)
{
this.p_id = id;
this.first_name = first_name;
this.mid_name = mid_name;
this.last_name = last_name;
this.p_age = age;
this.p_sex = sex;
}
private int p_id = -1;
private string first_name = String.Empty;
private string mid_name = String.Empty;
private string last_name = String.Empty;
private short p_age = 0;
private char? p_sex = null;
public int ID
{
get
{
return p_id;
}
set
{
p_id = value;
}
}
public string FirstName
{
get
{
return first_name;
}
set
{
first_name = value;
}
}
public string MiddleName
{
get
{
return mid_name;
}
set
{
mid_name = value;
}
}
public string LastName
{
get
{
return last_name;
}
set
{
last_name = value;
}
}
public short Age
{
get
{
return p_age;
}
set
{
p_age = value;
}
}
public char? Sex
{
get
{
return p_sex;
}
set
{
p_sex = value;
}
}
}
}
VB.NET
Imports System
Imports System.Collections.Generic
Imports System.Text
Public Class Person
Public Sub New()
End Sub
Public Sub New(ByVal id As Integer, ByVal first_name As String, ByVal mid_name As String, ByVal last_name As String, ByVal age As Short, ByVal sex As Char)
Me.p_id = id
Me.first_name = first_name
Me.mid_name = mid_name
Me.last_name = last_name
Me.p_age = age
Me.p_sex = sex
End Sub
Private p_id As Integer = -1
Private first_name As String = String.Empty
Private mid_name As String = String.Empty
Private last_name As String = String.Empty
Private p_age As Short = 0
Private p_sex As Nullable(Of Char) = Nothing
Public Property ID() As Integer
Get
Return p_id
End Get
Set(ByVal value As Integer)
p_id = value
End Set
End Property
Public Property FirstName() As String
Get
Return first_name
End Get
Set(ByVal value As String)
first_name = value
End Set
End Property
Public Property MiddleName() As String
Get
Return mid_name
End Get
Set(ByVal value As String)
mid_name = value
End Set
End Property
Public Property LastName() As String
Get
Return last_name
End Get
Set(ByVal value As String)
last_name = value
End Set
End Property
Public Property Age() As Short
Get
Return p_age
End Get
Set(ByVal value As Short)
p_age = value
End Set
End Property
Public Property Sex() As Nullable(Of Char)
Get
Return p_sex
End Get
Set(ByVal value As Nullable(Of Char))
p_sex = value
End Set
End Property
End Class
Note: If you are using C# 3.0, you can use a new feature called ‘Automatic properties’ See how simple it is to create properties:
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string MiddleName { get; set; }
public int Age { get; set; }
public char Sex { get; set; }
VB.NET does not support automatic properties.
Now go to the Program.cs or Module.vb and write the following code to add Person objects to the List(T) collection:
C#
static void Main(string[] args)
{
List<Person> pList = new List<Person>();
pList.Add(new Person(1, "John", "", "Shields", 29, 'M'));
pList.Add(new Person(2, "Mary", "Matthew", "Jacobs", 35, 'F'));
pList.Add(new Person(3, "Amber", "Carl", "Agar", 25, 'M'));
pList.Add(new Person(4, "Kathy", "", "Berry", 21, 'F'));
pList.Add(new Person(5, "Lena", "Ashco", "Bilton", 33, 'F'));
pList.Add(new Person(6, "Susanne", "", "Buck", 45, 'F'));
pList.Add(new Person(7, "Jim", "", "Brown", 38, 'M'));
pList.Add(new Person(8, "Jane", "G", "Hooks", 32, 'F'));
pList.Add(new Person(9, "Robert", "", "", 31, 'M'));
pList.Add(new Person(10, "Cindy", "Preston", "Fox", 25, 'F'));
pList.Add(new Person(11, "Gina", "", "Austin", 27, 'F'));
pList.Add(new Person(12, "Joel", "David", "Benson", 33, 'M'));
pList.Add(new Person(13, "George", "R", "Douglas", 55, 'M'));
pList.Add(new Person(14, "Richard", "", "Banks", 22, 'M'));
pList.Add(new Person(15, "Mary", "C", "Shaw", 39, 'F'));
}
VB.NET
Sub Main()
Dim pList As List(Of Person) = New List(Of Person)()
pList.Add(New Person(1, "John", "", "Shields", 29, "M"c))
pList.Add(New Person(2, "Mary", "Matthew", "Jacobs", 35, "F"c))
pList.Add(New Person(3, "Amber", "Carl", "Agar", 25, "M"c))
pList.Add(New Person(4, "Kathy", "", "Berry", 21, "F"c))
pList.Add(New Person(5, "Lena", "Ashco", "Bilton", 33, "F"c))
pList.Add(New Person(6, "Susanne", "", "Buck", 45, "F"c))
pList.Add(New Person(7, "Jim", "", "Brown", 38, "M"c))
pList.Add(New Person(8, "Jane", "G", "Hooks", 32, "F"c))
pList.Add(New Person(9, "Robert", "", "", 31, "M"c))
pList.Add(New Person(10, "Cindy", "Preston", "Fox", 25, "F"c))
pList.Add(New Person(11, "Gina", "", "Austin", 27, "F"c))
pList.Add(New Person(12, "Joel", "David", "Benson", 33, "M"c))
pList.Add(New Person(13, "George", "R", "Douglas", 55, "M"c))
pList.Add(New Person(14, "Richard", "", "Banks", 22, "M"c))
pList.Add(New Person(15, "Mary", "C", "Shaw", 39, "F"c))
End Sub
I have also created a common method ‘PrintOnConsole’ that will help us print the List(T) on the console:
C#
static void PrintOnConsole(List<Person> pList, string info)
{
Console.WriteLine(info);
Console.WriteLine("\n{0,2} {1,7} {2,8} {3,8} {4,2} {5,3}",
"ID", "FName", "MName", "LName", "Age", "Sex");
pList.ForEach(delegate(Person per)
{
Console.WriteLine("{0,2} {1,7} {2,8} {3,8} {4,2} {5,3}",
per.ID, per.FirstName, per.MiddleName, per.LastName, per.Age, per.Sex);
});
Console.ReadLine();
}
VB.NET
Sub PrintOnConsole(ByVal pList As List(Of Person), ByVal info As String)
Console.WriteLine(info)
Console.WriteLine(vbLf & "{0,2} {1,7} {2,8} {3,8} {4,2} {5,3}", "ID", "FName", "MName", "LName", "Age", _
"Sex")
For Each per As Person In pList
Console.WriteLine("{0,2} {1,7} {2,8} {3,8} {4,2} {5,3}", per.ID, per.FirstName, per.MiddleName, per.LastName, per.Age, per.Sex)
Next
Console.ReadLine()
End Sub
Note: VB.NET does not support anonymous methods.
With the base code set, let us see some common operations with the Generic List(T), in our case the List<Person> collection:
1. Looping through all items in the List(T)
C#
PrintOnConsole(pList, "1. --- Looping through all items in the List<T> ---");
VB.NET
PrintOnConsole(pList, "1. --- Looping through all items in the List<T> ---")
2. Filtering List(T) using a single condition - (Age > 35)
C#
List<Person> filterOne = pList.FindAll(delegate(Person p) { return p.Age > 35; });
PrintOnConsole(filterOne, "2. --- Filtering List<T> on single condition (Age > 35) ---");
VB.NET
Dim filterOne As List(Of Person) = pList.FindAll(Function(p As Person) p.Age > 35)
PrintOnConsole(filterOne, "2. --- Filtering List<T> on single condition (Age > 35) ---")
3. Filtering List(T) on multiple conditions (Age > 35 and Sex is Female)
C#
List<Person> filterMultiple = pList.FindAll(delegate(Person p) { return p.Age > 35 && p.Sex == 'F'; });
PrintOnConsole(filterMultiple, "3. --- Filtering List<T> on multiple conditions (Age > 35 and Sex is Female) ---");
VB.NET
Dim filterMultiple As List(Of Person) = pList.FindAll(Function(p As Person) p.Age > 35 AndAlso p.Sex = "F"c)
PrintOnConsole(filterMultiple, "3. --- Filtering List<T> on multiple conditions (Age > 35 and Sex is Female) ---")
4. Sorting List(T) (Sort on FirstName)
C#
List<Person> sortFName = pList;
sortFName.Sort(delegate(Person p1, Person p2)
{
return p1.FirstName.CompareTo(p2.FirstName);
});
PrintOnConsole(sortFName, "4. --- Sort List<T> (Sort on FirstName) ---");
VB.NET
Dim sortFName As List(Of Person) = pList
sortFName.Sort(Function(p1 As Person, p2 As Person) p1.FirstName.CompareTo(p2.FirstName))
PrintOnConsole(sortFName, "4. --- Sort List<T> (Sort on FirstName) ---")
5. Sorting List(T) descending (Sort on LastName descending)
C#
List<Person> sortLNameDesc = pList;
sortLNameDesc.Sort(delegate(Person p1, Person p2)
{
return p2.LastName.CompareTo(p1.LastName);
});
PrintOnConsole(sortLNameDesc, "5. --- Sort List<T> descending (Sort on LastName descending) ---");
VB.NET
Dim sortLNameDesc As List(Of Person) = pList
sortLNameDesc.Sort(Function(p1 As Person, p2 As Person) p2.LastName.CompareTo(p1.LastName))
PrintOnConsole(sortLNameDesc, "5. --- Sort List<T> descending (Sort on LastName descending) ---")
6. Add new List(T) to existing List(T)
C#
List<Person> newList = new List<Person>();
newList.Add(new Person(16, "Geoff", "", "Fisher", 29, 'M'));
newList.Add(new Person(17, "Samantha", "Carl", "Baxer", 32, 'F'));
pList.AddRange(newList);
PrintOnConsole(pList, "6. --- Add new List<T> to existing List<> ---");
VB.NET
Dim newList As List(Of Person) = New List(Of Person)()
newList.Add(New Person(16, "Geoff", "", "Fisher", 29, "M"c))
newList.Add(New Person(17, "Samantha", "Carl", "Baxer", 32, "F"c))
pList.AddRange(newList)
PrintOnConsole(pList, "6. --- Add new List<T> to existing List<> ---")
7. Remove multiple items from List(T) based on condition (remove male employees)
C#
List<Person> removeList = pList;
removeList.RemoveAll(delegate(Person p) { return p.Sex == 'M'; });
PrintOnConsole(removeList, "7. --- Remove multiple items from List<> based on condition ---");
VB.NET
Dim removeList As List(Of Person) = pList
removeList.RemoveAll(Function(p As Person) p.Sex = "M"c)
PrintOnConsole(removeList, "7. --- Remove multiple items from List<> based on condition ---")
8. Create Read Only List(T)
C#
Console.WriteLine("8. --- Create Read Only List<> ---");
IList<Person> personReadOnly = pList;
Console.WriteLine("Before - Is List Read Only? True or False : " + personReadOnly.IsReadOnly);
personReadOnly = pList.AsReadOnly();
Console.WriteLine("After - Is List Read Only? True or False : " + personReadOnly.IsReadOnly);
Console.ReadLine();
VB.NET
Console.WriteLine("Create Read Only List<>")
Dim personReadOnly As IList(Of Person) = pList
Console.WriteLine("Before - Is List Read Only? True or False : " & personReadOnly.IsReadOnly)
personReadOnly = pList.AsReadOnly()
Console.WriteLine("After - Is List Read Only? True or False : " & personReadOnly.IsReadOnly & "</br>")
Well those were some common operations with the Generic Collection List(T). In the next article, I will demonstrate how to carry the same operations using the new features of C# 3.0 and VB.NET. I hope this article was useful and I thank you for viewing it. The entire source code of this article in C# and VB.NET can be dowloaded from here
This article has been editorially reviewed by Suprotim Agarwal.
C# and .NET have been around for a very long time, but their constant growth means there’s always more to learn.
We at DotNetCurry are very excited to announce The Absolutely Awesome Book on C# and .NET. This is a 500 pages concise technical eBook available in PDF, ePub (iPad), and Mobi (Kindle).
Organized around concepts, this Book aims to provide a concise, yet solid foundation in C# and .NET, covering C# 6.0, C# 7.0 and .NET Core, with chapters on the latest .NET Core 3.0, .NET Standard and C# 8.0 (final release) too. Use these concepts to deepen your existing knowledge of C# and .NET, to have a solid grasp of the latest in C# and .NET OR to crack your next .NET Interview.
Click here to Explore the Table of Contents or Download Sample Chapters!
Was this article worth reading? Share it with fellow developers too. Thanks!
Suprotim Agarwal, MCSD, MCAD, MCDBA, MCSE, is the founder of
DotNetCurry,
DNC Magazine for Developers,
SQLServerCurry and
DevCurry. He has also authored a couple of books
51 Recipes using jQuery with ASP.NET Controls and
The Absolutely Awesome jQuery CookBook.
Suprotim received the prestigious Microsoft MVP award for 17 consecutive years, until he resigned from the program in 2025. In a professional capacity, he is the CEO of A2Z Knowledge Visuals Pvt Ltd, a digital group that offers Digital Marketing and Branding services to businesses, both in a start-up and enterprise environment.
Get in touch with him on Twitter @suprotimagarwal or at LinkedIn