Name the theme of "Araby." What textual evidence backs this up? How do you compare/contrast “Araby” to “I Want To Know Why”? How do you compare/contrast “Araby” to The House On Mango Street?

The major themes in "Araby" are longing/desire and disillusion/loss of innocence. Interestingly, both The House on Mango Street and "I Want To Know Why" share the same themes as "Araby."
In "Araby," the unnamed narrator is infatuated with Mangan's sister. He tries to get as many glimpses of her as he can. The narrator believes that his friend's sister is the epitome of elegance, beauty, and goodness. He daydreams about her and imagines going to the bazaar to bring back a gift for her. In the end, however, his hopes are disappointed when he arrives at the bazaar too late to purchase anything of significance or value. The narrator begins to understand that love is more complicated than he imagines. 
In "I Want To Know Why," the unnamed narrator is fascinated by horses. He especially adores Sunstreak, a stallion, and is so enchanted with the horse that his emotions become overwhelmed when he thinks about the animal. In time, the narrator also comes to admire Jerry Tillford, Sunstreak's trainer. When he thinks of Jerry, he experiences feelings akin to worship. The narrator believes that Jerry loves horses as much as he does. He is disillusioned however, when he discovers that Jerry has interests outside of horses. The narrator is particularly disgusted when he discovers Jerry's outside interests entail cavorting with prostitutes. The themes of longing and disillusion are apparent in this coming-of-age story.
In The House on Mango Street, Esperanza dreams of leaving her dilapidated house and her poverty-stricken neighborhood. She yearns for freedom, excitement, and love, all factors that are missing from her current life. Esperanza believes that her neighborhood has little to offer her, but as puberty arrives, she discovers that she is beginning to harbor new thoughts and to feel strange new longings. Like "Araby" and "I Want To Know Why," The House on Mango Street is a bildungsroman. The narrators in all three stories long for things that are just beyond their reach, whether it be horses or a member of the opposite sex.
Unlike "Araby" and "I Want to Know Why," however, the narrator in The House on Mango Street acquires a pragmatic optimism. Esperanza's resolve to leave Mango Street is reinforced by her traumatic sexual assault. However, she soon realizes that much has to happen before she can leave. So, she turns to her writing as a form of catharsis, as a therapeutic exercise, if you will. Even though Esperanza's innocence is lost, she begins to understand the value of waiting and preparing. Her longing is still intact, however; her traumatic experiences and disappointments do not enervate her in the way it does her peers in "Araby" and "I Want To Know Why." Unlike these two stories, The House on Mango Street ends on a hopeful note.