What literary techniques are used by Oscar Wilde in The Picture of Dorian Gray in order to get his message across to his readers?

In The Picture of Dorian Gray, Wilde uses a number of literary devices to emphasize some of the book's key themes.

First of all, Wilde uses a number of symbols to reinforce a key theme. The yellow book, for example, which Dorian receives from Lord Henry in Chapter Ten, functions as a representation of Dorian's downward spiral into hedonism and corruption. The significance of this book is summed up in the text: "Things of which he had never dreamed were gradually revealed." Similarly, in Chapter 16, the opium dens act as potent symbols of Dorian's corrupted soul. Secondly, Wilde uses another technique called foreshadowing to emphasize the importance of future events. In the first chapter, for instance, changes in the natural environment of Basil's studio foreshadow the importance of Dorian's introduction to Lord Henry.

Secondly, Wilde uses another technique called foreshadowing to emphasize the importance of future events. In the first chapter, for instance, changes in the natural environment of Basil's studio foreshadow the importance of Dorian's introduction to Lord Henry: 

The wind shook some blossoms from the trees, and the heavy lilac-blooms, with their clustering stars, moved to and fro in the languid air.

Later, in Chapter Six, James Vane's constant references to Sybil's safety suggest that something sinister will befall her. In the same way, James's repeated threat, that he will kill Dorian if he hurts Sybil, foreshadows his attempt on Dorian's life in Chapter 16. Foreshadowing, therefore, builds suspense ahead of some of the novel's most important plot twists.