using 是非托管资源: 解析:在C#应用托管到.NET Framework.但是他可以释放非托管资源. using 关键字有两个作用: 1:作为关键字,using可以导入命名空间 2:座位C#语句,using可以释放对象占用的内存资源 using 关键字的使用: ****用了using,还是需要try-catch的 ****SQLHelper 使用using的地方: using (SqlConnection con=new SqlConnection(Constr)) { using (Sq
Petya loves lucky numbers. Everybody knows that lucky numbers are positive integers whose decimal representation contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not. Petya has an array consisting o