The NSAttributedString type represents a string that has a series of attributes applied uniformly.

The companion Foundation.NSMutableAttributedString type can be used to create attributed strings that have overlapping attributes and whose contents can be modified after creation.

These types typically are used to attach information to elements of the string that dictate the font and colors to use as well as rendering attributes like kerning or how to render ligatures on a specific run of code.

These classes do not dictate the meaning or behavior of the attributes on a string, they merely keep track of the attributes. The actual meaning of these attributes is interpreted by the consumer of these objects.

NSAttributedStrings are created with a string and a set of attributes. The default constructor takes a string and an NSDictionary object where the keys represent the attributes and the values on each element represent the value of that attribute.

To simplify many common scenarios, MonoTouch provides constructors with strong-types to easily create attributed strings for use with CoreText or UIKit. These constructors provide type-safety and eliminate programming errors caused by accidentally creating attributes that are not recognized by a backend.

To create NSAttributedStrings that you can use with CoreText's rendering, you create an instance of the CoreText.CTStringAttributes class, set its properties to the attributes that you desire, and then invoke the NSAttributedString constructor with it.

To create NSAttributedStrings that you can use with UIKit's rendering, you create an instance of the UIKit.UIStringAttributes class, set its properties to the attributes that you desire, and then invoke the NSAttributedString constructor with it.

The examples below show how to use the C# object initializer syntax to initialize the CTStringAttributes and the UIStringAttributes to setup your attributes. You can later use these attributes multiple times with different attributed strings:

// 
// Using NSAttributedString with CoreText
//
var attributedString = new NSAttributedString ("Hello, world",
       new CTStringAttributes () {
              ForegroundColorFromContext =  true,
              Font = new CTFont ("Arial", 24)
       });

// Pass the NSAttributedString to a CTLine and draw the CTLine.
using (var textLine = new CTLine (attributedString)) {
       textLine.Draw (gctx);
}

// 
// Using NSAttributedString with UIKit
//
var myText = new NSAttributedString ("Hello, world",
       new UIStringAttributes () {
              ForegroundColor =  UIColor.Red,
	      KerningAdjustment = 3
       });
label.AttributedText = myText;
	

While both CoreText.CTStringAttributes and UIKit.UIStringAttributes are useful to create attributes that can later be used with attributed strings, it is also possible to use the NSAttributedString() constructor with C# named parameters for quickly creating attributed strings inline.

//
// This example shows how to create an NSAttributedString for
// use with UIKit without creating the attributes separately
//
var text = new NSAttributedString (
    "Hello, World",
    font: UIFont.FromName ("HoeflerText-Regular", 24.0f),
    foregroundColor: UIColor.Red,
    strokeWidth: 4
);
	

It is also possible to create NSAttributedStrings with the NSDictionary API, although that does not offer any type safety nor prevents common errors. To use it, you typically use the various NSString properties that end in "AttributedName" that are part of this class.

//
// This example shows how to create an NSAttributedString for
// use with UIKit using NSDictionaries
//
var dict = new NSMutableDictionary () {
    { NSAttributedString.FontAttributeName, UIFont.FromName ("HoeflerText-Regular", 24.0f), },
    { NSAttributedString.ForegroundColorAttributeName, UIColor.Black }
};

var text = new NSAttributedString (
	"Hello, World", dict);