Assignment
A string value is specified inside quotation marks "":
"Daniel"
We can declare it with the full type name:
System.String name = "Daniel";
But nobody does that. We can use the alias instead which is string:
string name = "Daniel";
Or we can use the var keyword:
var name = "Daniel";
We can initialize a string with the an empty value "" or with the literal string.Empty:
var name = string.Empty;
Empty strings
We could have used "" to signify an empty string, but you can use string.Empty which is more elegant.
If we want to declare a null string, we can just declare it and not assign it:
string name;
WARNING
Notice that this time we used string and not var.
It's impossible to use var when you don't assign a value (the compiler cannot infer the type).
IsNullOrEmpty method
We can check to see whether a string is null or empty:
if (String.IsNullOrEmpty(name))
Console.WriteLine($"{nameof(name)} is empty.");
Constant strings
Many times, you will see that strings are defined as const. In this way, you can make strings that you cannot change (aka reassign):
const string message = "Persistent string";
// This gives an error
message = "new value";
const vs readonly
You can make an instance field constant like so:
public const string Message = "Persistent string";
This makes the variable Message not able to hold / point to another value. But you can make it readonly as well:
public readonly string Message = "Persistent string";
const vs readonly
The difference here is that you can now reassign the value of Message, but only in the constructor or a variable initializer.
Looping
In essence the string type is an array of characters which means that we can iterate over it with foreach as we would normally do with arrays:
foreach (var character in text)
{
Console.WriteLine(character);
}
So, because internally a string is a collection of Char objects, we can use foreach. It is moreover a readonly collection, for we know that strings are immutable.
Conversion
We can also convert an Array of char items into a string:
var charArray = new[] { 'C', 'o', 'd', 'e' };
string message = new String(charArray);
Console.WriteLine(message);
ToString
We call the ToString() method which converts any object to a string:
var age = 21;
var ageAsString = age.ToString();
Console.WriteLine(ageAsString); //21