In visual basic, List is a generic type of collection so it will allow storing only strongly typed objects i.e. elements of same data type and the size of list will vary dynamically based on our application requirements like adding or removing elements from the list.
In visual basic, the list is same as an arraylist but the only difference is arraylist is a non-generic type of collection. So, it will allow storing elements of different data types.
In visual basic, list is a generic type of collection and it is provided by System.Collections.Generic namespace.
As discussed, the collection is a class so to define a list, we must need to declare an instance of the list class before we perform any operations like add, delete, etc. like as shown below.
If you observe the above list declaration, we created a generic list (lst) with an instance of List class using type parameter (T) as a placeholder with brackets (Of type).
Here, the bracketed item (Of T) will indicate that the list is a generic type and type parameter (T) is used to represent a type of elements to be accepted by the list.
In visual basic, the generic list (List(Of T)) is an implementation of IList(Of T) interface so we can also use the IList(Of T) interface to create an object of the generic list (List(Of T)) like as shown below.
Dim lst As IList(Of T) = New List(Of T)()
Following is the example of initializing a generic list by specifying the required type to accept values to store.
If you observe the above example, we defined a list (lst) with String data type to store only string elements.
The following are some of the commonly used properties of the generic list in a visual basic programming language.
| Property | Description |
|---|---|
| Capacity | It is used to get or set the number of elements a list can contain. |
| Count | It is used to get the number of elements in list. |
| Item | It is used get or set an element at the specified index. |
Following are the some of commonly used methods of generic list to perform add, search, insert, delete or sort operations in a visual basic programming language.
| Method | Description |
|---|---|
| Add | It is used to add an element at the end of the List. |
| AddRange | It is used to add all the elements of specified collection at the end of the List. |
| Clear | It will remove all the elements from the List. |
| Contains | It is used to determine whether the specified element exists in the List or not. |
| CopyTo | It is used to copy entire List to a compatible one-dimensional array. |
| Find | It is used to search for an element that matches the conditions defined by the specified predicate and returns the first occurrence of the List. |
| FindAll | It is used to retrieve all the elements that matches the conditions defined by the specified predicate. |
| ForEach | It is used to iterate through the List to access elements. |
| Insert | It is used to insert an element into the list at the specified index. |
| InsertRange | It is used to insert all the elements of specified collection into List starting from the specified index. |
| Remove | It is used to remove the first occurrence of specified element from the List. |
| RemoveAt | It is used to remove an element from the list based on the specified index position. |
| RemoveRange | It is used to remove a range of elements from the List. |
| Reverse | It reverses the order of List elements. |
| Sort | It sorts the elements in the List. |
| ToArray | It will copies the elements of List to new array object. |
Following is the example of using the generic list (List(Of T)) in visual basic programming language.
Module Module1
Sub Main(ByVal args As String())
' Creating and initializing list
Dim lst As List(Of Integer) = New List(Of Integer)()
lst.Add(1)
lst.Add(8)
lst.Add(45)
Dim lst2 As List(Of String) = New List(Of String)()
lst2.Add("Hi")
lst2.Add("Welcome")
lst2.Add("to")
lst2.Add("Tutlane")
Console.WriteLine("List1 Elements Count: " & lst.Count)
Console.WriteLine("List1 Capacity: " & lst.Capacity)
Console.WriteLine("*********List1 Elements********")
' Accessing list elements
For Each item In lst
Console.WriteLine(item)
Next
Console.WriteLine("List2 Elements Count: " & lst2.Count)
Console.WriteLine("List2 Capacity: " & lst2.Capacity)
Console.WriteLine("*********List2 Elements********")
For Each item In lst2
Console.WriteLine(item)
Next
Console.ReadLine()
End Sub
End Module
If you observe the above example, we are able to define a new generic lists (lst, lst2) collection. Here, we added only the defined data type (Integer, String) values to the newly created lists (lst, lst2) by using the Add method and accessing the generic list (lst, lst2) elements by using For Each loop.
When we execute the above visual basic program, we will get the result as shown below.
This is how we can use the generic list in visual basic to store the group of defined type elements based on our requirements.
Following are the some of useful examples to work with generic list in visual basic programming language.
In visual basic, we can add elements to the list either by using Add / AddRange methods or at the time of initialization based on our requirements.
Following is the example of adding elements to the list using Add or AddRange methods in visual basic.
Module Module1
Public Class User
Public Property Id As Integer
Public Property Name As String
Public Property Location As String
End Class
Sub Main(ByVal args As String())
' Creating and initializing list
Dim lst As List(Of Integer) = New List(Of Integer)() From {1, 8, 45, 70}
Console.WriteLine("List1 Elements Count: " & lst.Count)
Console.WriteLine("*********List1 Elements********")
' Accessing list elements
For Each item In lst
Console.WriteLine(item)
Next
' AddRange method
Dim lst2 As List(Of Integer) = New List(Of Integer)()
lst2.AddRange(lst)
Console.WriteLine("List2 Elements Count: " & lst2.Count)
Console.WriteLine("*********List2 Elements********")
For Each item In lst2
Console.WriteLine(item)
Next
Dim users As List(Of User) = New List(Of User)() From {
New User With {
.Id = 1,
.Name = "Suresh Dasari",
.Location = "Hyderabad"
},
New User With {
.Id = 2,
.Name = "Rohini Alavala",
.Location = "Guntur"
}
}
users.Add(New User With {
.Id = 3,
.Name = "Trishika Dasari",
.Location = "Guntur"
})
users.Add(New User With {
.Id = 4,
.Name = "Praveen Alavala",
.Location = "Eluru"
})
Console.WriteLine("List3 Elements Count: " & users.Count)
Console.WriteLine("*********List3 Elements********")
For Each u As User In users
Console.WriteLine("Id:{0}, Name:{1}, Location:{2}", u.Id, u.Name, u.Location)
Next
Console.ReadLine()
End Sub
End Module
If you observe the above example, we created multiple lists (lst, lst2, users) and adding elements to the lists in different ways like added some of the elements during the initialization time and some other elements by using Add & AddRange methods.
When we execute the above visual basic program, we will get the result as shown below.
In visual basic, we have a different ways to access list elements i.e. either by using index positions or by iterating through the list using For / For Each loops.
Following is the example of accessing a list elements in different ways.
Module Module1
Public Class User
Public Property Id As Integer
Public Property Name As String
Public Property Location As String
End Class
Sub Main(ByVal args As String())
' Creating and initializing list
Dim lst As List(Of Integer) = New List(Of Integer)() From {1, 8, 45, 70}
Console.WriteLine("*********Access Elements with Index Position********")
Console.WriteLine("Element at 0: " & lst(0))
Console.WriteLine("Element at 2: " & lst(2))
' Creating List
Dim users As List(Of User) = New List(Of User)() From {
New User With {
.Id = 1,
.Name = "Suresh Dasari",
.Location = "Hyderabad"
},
New User With {
.Id = 2,
.Name = "Rohini Alavala",
.Location = "Guntur"
},
New User With {
.Id = 3,
.Name = "Trishika Dasari",
.Location = "Guntur"
},
New User With {
.Id = 4,
.Name = "Praveen Alavala",
.Location = "Eluru"
}
}
Console.WriteLine("*********Access Elements with For Loop********")
' For loop to access list elements
For i As Integer = 0 To users.Count - 1
Console.WriteLine("Id:{0}, Name:{1}, Location:{2}", users(i).Id, users(i).Name, users(i).Location)
Next
Console.WriteLine("*********Access Elements with Foreach Loop********")
' For Each loop to access list elements
For Each u As User In users
Console.WriteLine("Id:{0}, Name:{1}, Location:{2}", u.Id, u.Name, u.Location)
Next
Console.ReadLine()
End Sub
End Module
If you observe the above example, we are accessing generic list elements in different ways by using index positions, For and For Each loops based on our requirements.
When we execute the above visual basic program, we will get the result like as shown below.
In visual basic, we can insert elements into the list either by using Insert() or InsertRange() methods.
Following is the example of inserting elements into the list by using Insert and InsertRange methods in visual basic.
Module Module1
Sub Main(ByVal args As String())
' Creating and initializing list
Dim lst As List(Of Integer) = New List(Of Integer)() From {1, 8, 45, 70}
' inserting elements into list
lst.Insert(0, 10)
lst.Insert(3, 50)
Dim lst2 As List(Of Integer) = New List(Of Integer)() From {200, 300}
' inserting lst2 into lst at position 2
lst.InsertRange(2, lst2)
Console.WriteLine("*********ArrayList Elements********")
For Each item In lst
Console.WriteLine(item)
Next
Console.ReadLine()
End Sub
End Module
If you observe the above example, we inserted elements into the list at different index positions (0, 3) by using the Insert() method. Same way, by using the InsertRange() method we are inserting all the elements of a newly created list (lst2) into lst at index position 2.
When we execute the above visual basic program, we will get the result as shown below.
In visual basic, we have different methods to remove elements from the list i.e. either by using Remove() or RemoveAt() or RemoveRange() methods.
Following is the example of deleting elements from the list in visual basic programming language.
ModuleModule1
Sub Main(ByVal args As String())
' Creating and initializing list
Dim lst As List(Of Integer) = New List(Of Integer)() From {10, 20, 30, 40, 50, 60, 70, 80}
' Removing an element which is having a value 50
lst.Remove(50)
' Removing an element at index 2
lst.RemoveAt(2)
' Removing 2 elements starting from index 3
lst.RemoveRange(3, 2)
Console.WriteLine("*********List Elements********")
For Each item In lst
Console.WriteLine(item)
Next
Console.ReadLine()
End Sub
End Module
If you observe the above example, we used Remove() method to delete the particular value of the element from the list and another method RemoveAt() is used to delete an element at the specified index position.
Same way, we used RemoveRange() method to delete the specified number of elements from the list starting from the specified index position.
When we execute the above visual basic program, we will get the result like as shown below.
In case, if you want to remove all the elements from the list, then use the Clear() method.
Same way, we can use different methods like Find() method to find the elements of list and Reverse() method to reverse the order of list elements, etc. based on our requirements.
By using Contains() method, we can check whether the specified element exists in the list or not. In case, if it exists it will return True otherwise False.
Following is the example of using Contains() method to check for an item that exists in the list or not in visual basic.
Module Module1
Sub Main(ByVal args As String())
' Creating and initializing list
Dim lst As List(Of Integer) = New List(Of Integer)() From {10, 20, 30, 40, 50, 60, 70, 80}
' Check for an item 50 exists in list or not
Console.WriteLine("Item Exists: " & lst.Contains(50))
Console.ReadLine()
End Sub
End Module
If you observe the above example, we used Contains() method to check for an item (50) exists in the list (lst) or not.
When we execute the above visual basic program, we will get the result as shown below.
The following are the important points that need to remember the list in visual basic.