It is not permissible to raise/keep a dog except for three (reasons): a hunting dog, a guard dog for herding livestock (and or protecting something) or a dog for farming, the Messenger of Allaah (ﷺ) said,
Whoever keeps a dog that is not a dog for hunting, herding livestock or farming, two qiraats will be deducted from his reward each day.
This is because keeping a dog is a means to filth, dirtying and harming the house due to it (i.e. the dog). The Prophet (ﷺ) ordered that a dish that is licked by a dog be washed seven times, one of which with dirt. So it is a must to stay away from this. Thus, staying away (from this affair is a must) except for the need of hunting, farming and guarding or herding livestock (or something valuable). As far as having them for other than these reason(s), is blind following and imitation of the Christians. So this is not permissible.