class Results
{
public auction result { get; set; }
}
class auction
{
public List<auctiondetail> auctions { get; set; }
}

class auctiondetail
    {
        public string category{ get; set; }
        public string userType{ get; set; }
        
        public string biz30Day { get; set; }//   销量：1758 
    }


private void test()
{
        string json={"result":{"auction":[{"biz30Day":35,"category":50010850,"userType":0},{"biz30Day":23,"category":50010850,"userType":0}]},"resultCode":0,"success":true};


　　　

Results result = new Results();
result = new JavaScriptSerializer().Deserialize<Results>(json);

if (result.result.auctions == null)
{

}
foreach (auctiondetail item in result.result.auctions)
{

}

 
}