public async Task ChangeVoteAsync(int productId, int userId, int newVote)
{
if (newVote < 0 || newVote > 5)
{
return;
}
var product = Products.Find(productId);
var vote = await ProductVotes.FindAsync(new object[] { productId, userId });
if (vote == null)
{
await ProductVotes.AddAsync(new ProductVote()
{
ProductId = productId, UserId = userId, Vote = newVote
});
var sum = product.Rating * product.CountOfVotes++;
product.Rating = (sum + newVote) / product.CountOfVotes;
}
else
{
var sum = product.Rating * product.CountOfVotes - vote.Vote;
vote.Vote = newVote;
product.Rating = (sum + newVote) / product.CountOfVotes;
}
await SaveChangesAsync();
}
public async Task <int> GetVoteAsync(int productId, int userId)
{
return((await ProductVotes.FindAsync(new object[] { productId, userId })).Vote);
}
public async Task <bool> IsVotedAsync(int productId, int userId)
{
return((await ProductVotes.FindAsync(new object[] { productId, userId })) != null);
}