Strings

A String is a sequence of characters. Strings are immutable: methods like ToUpper return a new string and leave the original alone.

Module Program
    Sub Main()
        Dim first = "Grace"
        Dim last = "Hopper"
        Dim full = first & " " & last

        Console.WriteLine(full)
        Console.WriteLine(full.Length)
        Console.WriteLine(full(0))
        Console.WriteLine(full.Substring(0, 5))
        Console.WriteLine(full.ToUpper())
        Console.WriteLine(full)
    End Sub
End Module

Grace Hopper
12
G
Grace
GRACE HOPPER
Grace Hopper

• & joins strings. + also works on two strings, but with numbers it adds instead, so always use & for text.
• full(0) is the first character — indexes start at 0.
• Substring(start, length) takes part of a string.

Quotes and special characters

VB strings have no backslash escapes. A double quote inside a string is written as two double quotes, and special characters come from constants:

Module Program
    Sub Main()
        Console.WriteLine("She said ""hello"".")
        Console.WriteLine("C:\Users\ada\notes.txt")
        Console.WriteLine("Line one" & vbCrLf & "Line two")
        Console.WriteLine("Name:" & vbTab & "Ada")
        Console.WriteLine("Also works:" & Environment.NewLine & "next line")
    End Sub
End Module

She said "hello".
C:\Users\ada\notes.txt
Line one
Line two
Name:	Ada
Also works:
next line

vbCrLf, vbLf, and vbTab are VB constants; Environment.NewLine is the platform's line ending. Backslashes are ordinary characters, which makes Windows paths easy.

Multi-line strings

Since VB 14, a string literal can span several lines:

Module Program
    Sub Main()
        Dim poem = "Roses are red,
Visual Basic is readable."
        Console.WriteLine(poem)
    End Sub
End Module

Roses are red,
Visual Basic is readable.

Interpolated strings

Module Program
    Sub Main()
        Dim item = "coffee"
        Dim price = 3.5D
        Dim qty = 3

        Console.WriteLine($"{qty} x {item} = {price * qty}")
        Console.WriteLine($"Total: {price * qty:F2}")
        Console.WriteLine($"Left |{item,-8}| Right |{qty,5}|")
        Console.WriteLine($"Braces: {{like this}}")
    End Sub
End Module

3 x coffee = 10.5
Total: 10.50
Left |coffee  | Right |    3|
Braces: {like this}

Inside $"...", {expr:format} applies a format (F2 = two decimals) and {expr,width} pads to a width (negative means left-aligned). Double the braces to print them literally.

Comparing strings

Module Program
    Sub Main()
        Console.WriteLine("apple" = "apple")
        Console.WriteLine("Apple" = "apple")
        Console.WriteLine(String.Equals("Apple", "apple", StringComparison.OrdinalIgnoreCase))
        Console.WriteLine("apple" < "banana")
        Console.WriteLine(String.IsNullOrEmpty(""))
    End Sub
End Module

True
False
True
True
True

The language is case-insensitive, but string values are compared case-sensitively by default (Option Compare Binary). Use StringComparison.OrdinalIgnoreCase when case shouldn't matter.

Practice

Store a first and last name in two variables and print the initials (like G.H.) and the full name in upper case, using an interpolated string.

Module Program
    Sub Main()
        Dim first = "Grace"
        Dim last = "Hopper"
        Console.WriteLine($"{first(0)}.{last(0)}. {(first & " " & last).ToUpper()}")
    End Sub
End Module

G.H. GRACE HOPPER