In visual basic, SortedList is a generic type of collection and it is useful to store a collection of key/value pairs that are sorted by key based on the associated IComparer(Of T) implementation.
By default, the sorted list will sort a key/value pairs in ascending order of the key and the sorted list will allow storing only the strongly-typed objects i.e. the key/value pairs of the specified data type.
In visual basic, the sorted list will allow us to store duplicate values but the keys must be unique and cannot be null to identify the values in sortedlist and the size of the sorted list will vary dynamically so we can add or remove elements from the sorted list based on our application requirements.
In visual basic, the sorted 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 sorted list, we must need to declare an instance of the sortedlist class before we perform any operations like add, delete, etc. like as shown below.
Dim slist As SortedList(Of TKey, TValue) = New SortedList(Of TKey, TValue)()
If you observe the above sortedlist declaration, we created a generic sortedlist (slst) with an instance of sortedlist class using type parameters (TKey, TValue) as placeholders within brackets.
Here, the brackets (Of TKey, Tvalue) will indicate that the sortedlist is a generic type and type parameter TKey is to represent the type of keys to be accepted by sortedlist and TValue is used to represent the type of values to be accepted by sortedlist.
Following is the example of initializing a generic sortedlist by specifying the required type for key and value.
Dim slist As SortedList(Of String, Integer) = New SortedList(Of String, Integer)()
If you observe the above example, we defined a sortedlist (slist) with the required key and value types to store. Here, the sortedlist will store a key of string type and value of int type.
Internally, the sortedlist will maintain a two object[] arrays, one for keys and another one for values so when we add key/value pair, it will perform a binary search using the key to find an appropriate index to store a key and value in respective arrays.
The following are some of the commonly used properties of generic sortedlist in a visual basic programming language.
| Property | Description |
|---|---|
| Capacity | It is used to get or set the number of elements a sortedlist can contain. |
| Count | It is used to get the number of key/value pair elements in the list. |
| Item[TKey] | It is used to get or set the value associated with the specified key. |
| Keys | It is used to get a collection of keys in sortedlist. |
| Values | It is used to get a collection of values in sortedlist. |
The following are some of the commonly used methods of generic sortedlist to perform add, search, insert, delete or sort operations in a visual basic programming language.
| Method | Description |
|---|---|
| Add | It is used to add elements with specified key and value in SortedList<TKey, TValue>. |
| Clear | It will remove all the elements from SortedList<TKey, TValue>. |
| ContainsKey | It is used to determine whether the specified key exists in the SortedList<TKey, TValue> or not. |
| ContainsValue | It is used to determine whether the specified value exists in SortedList<TKey, TValue> or not. |
| IndexOfKey | It is used to get the index value of specified key stored in the SortedList<TKey, TValue>. |
| IndexOfValue | It is used to get the index value of specified value stored in the SortedList<TKey, TValue>. |
| Remove | It is used to remove an element from SortedList<TKey, TValue> with specified key. |
| RemoveAt | It is used to remove an element at the specified index position from SortedList<TKey, TValue>. |
| TryGetValue | It is used to get the value associated with the specified key. |
In visual basic, while adding elements to sortedlist we need to make sure that there will not be any duplicate keys because sortedlist will allow us to store duplicate values but keys must be unique to identify the values in the list.
Following is the example of adding a key/value pair elements to sorted list in different ways.
Module Module1
Sub Main(ByVal args As String())
' Create a new sorted list with int keys and string values.
Dim slst As SortedList(Of Integer, String) = New SortedList(Of Integer, String)()
' Add elements to the list. No duplicate keys allowed but values can be duplicate
slst.Add(1, "Suresh")
slst.Add(4, "Rohini")
slst.Add(2, "Trishi")
slst.Add(3, Nothing)
' Another way to add elements. If key not exist, then that key adds a new key/value pair
slst(5) = "Trishi"
' Add method throws exception if key already in the list
Try
slst.Add(2, "Praveen")
Catch __unusedArgumentException1__ As ArgumentException
Console.WriteLine("An element with Key = '2' already exists.")
End Try
Console.WriteLine("*********List1 Elements********")
' Accessing elements as KeyValuePair objects
For Each item As KeyValuePair(Of Integer, String) In slst
Console.WriteLine("Key = {0}, Value = {1}", item.Key, item.Value)
Next
' Creating and initializing list
Dim slst2 As SortedList(Of String, Integer?) = New SortedList(Of String, Integer?) From {
{"msg2", 1},
{"msg3", 20},
{"msg4", 100},
{"msg1", Nothing}
}
Console.WriteLine("*********List2 Elements********")
' Accessing elements as KeyValuePair objects
For Each item As KeyValuePair(Of String, Integer?) In slst2
Console.WriteLine("Key = {0}, Value = {1}", item.Key, item.Value)
Next
Console.ReadLine()
End Sub
End Module
If you observe the above example, we are able to define a new generic sortedlist (slst, slst2) collections. Here, we added only the defined data type keys and values to the newly created lists (slst, slst2) in different ways.
As discussed, the Add method will throw an exception in case if we try to add a key (2) which is already existing so to handle that exception we used a try-catch block.
When we execute the above visual basic program, we will get the result as shown below.
If you observe the above result, by default all the list elements are sorted in ascending order based on the key and we got an exception when we tried to add a key (2) which is already existing and added a key (5) which is not existing in the list.
In visual basic, we have different ways to access sorted list elements i.e. either by using index positions or by iterating through the list using For / For Each loop.
Following is the example of accessing the sortedlist elements in different ways.
Module Module1
Sub Main(ByVal args As String())
' Create new sorted list
Dim slst As SortedList(Of Integer, String) = New SortedList(Of Integer, String)()
slst.Add(1, "Suresh")
slst.Add(4, "Rohini")
slst.Add(2, "Trishi")
slst.Add(3, "Praveen")
' Access value with key
Dim val1 As String = slst(2)
' Access value with index position
Dim val2 As String = slst.Values(2)
' Access key with index position
Dim val3 As Integer = slst.Keys(2)
Console.WriteLine("******Access Elements with Key, Index Position*****")
Console.WriteLine("Value at Key '2': " & val1)
Console.WriteLine("Value at Index '2': " & val2)
Console.WriteLine("Key at Index '2': " & val3)
Console.WriteLine("*********Access Elements with Foreach Loop********")
For Each item As KeyValuePair(Of Integer, String) In slst
Console.WriteLine("Key = {0}, Value = {1}", item.Key, item.Value)
Next
Console.WriteLine("*********Access Elements with For Loop********")
For i As Integer = 0 To slst.Count - 1
Console.WriteLine("Key = {0}, Value = {1}", slst.Keys(i), slst.Values(0))
Next
Console.WriteLine("*********Sorted List Keys********")
For Each item In slst.Keys
Console.WriteLine("Key = {0}", item)
Next
Console.WriteLine("*********Sorted List Values********")
For Each item In slst.Values
Console.WriteLine("Value = {0}", item)
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 loop based on our requirements.
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 sorted list i.e. either by using Remove() or RemoveAt() methods.
Following is the example of deleting elements from the sorted list in visual basic programming language.
Module Module1
Sub Main(ByVal args As String())
' Create new sorted list
Dim slst As SortedList(Of Integer, String) = New SortedList(Of Integer, String)()
slst.Add(1, "Suresh")
slst.Add(4, "Rohini")
slst.Add(2, "Trishi")
slst.Add(3, "Praveen")
slst.Add(5, "Sateesh")
' Remove element with key 2
slst.Remove(2)
' Remove element at index position 2
slst.RemoveAt(2)
Console.WriteLine("*********Access Sorted List Elements********")
Console.WriteLine()
For Each item As KeyValuePair(Of Integer, String) In slst
Console.WriteLine("Key = {0}, Value = {1}", item.Key, item.Value)
Next
Console.ReadLine()
End Sub
End Module
If you observe the above example, we used the Remove() method to delete the particular key of an element from the list and used RemoveAt() method to delete element at the specified index position.
When we execute the above visual basic program, we will get the result as shown below.
In case, if you want to remove all the elements from the sorted list, use the Clear() method.
By using ContainsKey() and ContainsValue() methods, we can check whether the specified element exists in the sorted list or not. In case, if it exists these methods will return True otherwise False.
Following is the example of using ContainsKey() and ContainsValue() methods to check for an item that exists in sorted list or not in visual basic.
Module Module1
Sub Main(ByVal args As String())
' Create new sorted list
Dim slst As SortedList(Of Integer, String) = New SortedList(Of Integer, String)()
slst.Add(1, "Suresh")
slst.Add(4, "Rohini")
slst.Add(2, "Trishi")
slst.Add(3, "Praveen")
slst.Add(5, "Sateesh")
Console.WriteLine("Contains Key 2: {0}", slst.ContainsKey(2))
Console.WriteLine("Contains Value 'Tutlane': {0}", slst.ContainsValue("Tutlane"))
Console.ReadLine()
End Sub
End Module
If you observe the above example, we used ContainsKey() and ContainsValue() methods to check for particular keys and values that exist in the sorted list (slst) or not.
When we execute the above visual basic program, we will get the result like as shown below.
Contains Key 2: True
Contains Value 'Tutlane': False
The following are the important points which we need to remember about the sorted list in visual basic.