Question

I’m trying to write a method that authenticate a user in the web apps. Here is the code:

public void SignIn(UserInfo Entity)
    {
        if(this.CheckUser(Entity.UserName, Entity.Password))

        {
            FormsAuthentication.RedirectFromLoginPage(Entity.UserName, false);
        }
        else
        {

        }
    }

    public bool CheckUser(String _UserName, string _Password)
    {
        using (var context = new TourBlogEntities1())
        {
            List<UserInfo> test = null;
            test = (from s in context.UserInfoes
                       where s.UserName == _UserName && s.Password == _Password
                       select s).ToList<UserInfo>();

            if(test==null)
            {
                return false;
            }
            else
            {
                return true;
            }

        }

    }

The problem is I can sign in with any username & password, which are not actually registered. What I have done wrong? Thanks in advance.

Answer 1

Your list is never null. You need to check whether your list contains a element.

I suggest you use the Any() or Count() method.

Any() – Determines whether a sequence contains any elements.

Count() – Returns a number that represents how many elements in the specified sequence satisfy a condition.

Sample

Any()

return (from s in context.UserInfoes
       where s.UserName == _UserName && s.Password == _Password
       select s).Any();

Count()

return (from s in context.UserInfoes
       where s.UserName == _UserName && s.Password == _Password
       select s).Count() != 0;

More Information

• MSDN – Enumerable.Any
• MSDN – Enumerable.Count