`Char.ToLower`, `ToUpper`

In VB.NET the Char class contains many helpful character-testing and manipulation functions. We can convert characters to lowercase and uppercase.

In addition to conversion, we can test characters with IsLower and IsUpper. This allows to develop complex imperative logical methods to test characters and parts of strings.

Example

This program is written in the VB.NET programming language and it modifies and tests characters. It uses ToLower, ToUpper, and then IsLower and IsUpper.

Part 1 We call Char.ToLower on the 4 characters we declared. We see that only the uppercase Char "C" was modified by this call.

Part 2 We call Char.ToUpper on the same 4 characters. The lowercase characters were returned by this case.

Part 3 We try to determine if the value "C" is an uppercase character, and IsUpper tells us that this is true.

Part 4 Meanwhile, IsLower returns True on the character value "a", meaning this is a lowercase character.

Module Module1
    Sub Main()
        Dim c1 = "a"c
        Dim c2 = "b"c
        Dim c3 = "C"c
        Dim c4 = "3"c
        Console.WriteLine($"INITIAL: {c1} {c2} {c3} {c4}")

        ' Part 1: use Char.ToLower.
        Dim lower1 = Char.ToLower(c1)
        Dim lower2 = Char.ToLower(c2)
        Dim lower3 = Char.ToLower(c3)
        Dim lower4 = Char.ToLower(c4)
        Console.WriteLine($"TOLOWER: {lower1} {lower2} {lower3} {lower4}")

        ' Part 2: use Char.ToUpper.
        Dim upper1 = Char.ToUpper(c1)
        Dim upper2 = Char.ToUpper(c2)
        Dim upper3 = Char.ToUpper(c3)
        Dim upper4 = Char.ToUpper(c4)
        Console.WriteLine($"TOUPPER: {upper1} {upper2} {upper3} {upper4}")

        ' Part 3: use Char.IsUpper.
        If Char.IsUpper(c3)
            Console.WriteLine($"Char {c3} is upper")
        End If

        ' Part 4: use Char.IsLower.
        If Char.IsLower(c1)
            Console.WriteLine($"Char {c1} is lower")
        End If
    End Sub
End ModuleINITIAL: a b C 3
TOLOWER: a b c 3
TOUPPER: A B C 3
Char C is upper
Char a is lower

It is better to use Char.ToLower and ToUpper to transform character cases instead of writing custom code, as the logic is already tested. IsLower and IsUpper are also useful tools.

Char.ToLower, ToUpper

Example

`Char.ToLower`, `ToUpper`