How many strings are allocated in each of the code snippets below?

VisualBasic Code Snippet

Dim s As String

s = "how"
s += " many"
s += " strings"
s += " are"
s += "allocated?"
Console.WriteLine(s)

C# Code Snippet

string s;

s = "how";
s += " many";
s += " strings";
s += " are";
s += "allocated?";
Console.WriteLine(s);

If you said one string was allocated, then... you are wrong. Five strings are actually allocated. Strings in the .NET framework are immutable. This means that each change the string s causes the runtime to create a new string and abandon the old one. The immutable nature of .NET strings should be considered when performance is a concern. The creation of temporary strings can be avoided using two methods:

• Use the String classes Concat, Join or Format methods to join multiple in a single statement
• Use the StingBuilder class to create dynamic (mutable) strings

Additional Resources
String class (Microsoft)
StringBuilder class (Microsoft)