Question

Can anyone help with some problems I have. I am trying to create an self made authentication method, im abit stuck in a few areas and was hoping some one could help. First thing I would like to ask is how to solve the problem I have commented in the code:

    public string Authentication(string studentID, string password)
    {
        var result = students.FirstOrDefault(n => n.StudentID == studentID);
        //find the StudentID that matches the string studentID 
        if (result != null)
        //if result matches then do this
        {
            //---------------------------------------------------------------------------- 
            byte[] passwordHash = Hash(password, result.Salt);
            string HashedPassword = Convert.ToBase64String(passwordHash);
            //----------------------------------------------------------------------------
            // take the specific students salt and generate hash/salt for string password (same way student.Passowrd was created)

            System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding();
            byte[] UserPassword = enc.GetBytes(HashedPassword);
            UserPassword.SequenceEqual(result.Password); // byte[] does not contain a definition for SequenceEqual?
            //check if the HashedPassword (string password) matches the stored student.Password
        }
        return result.StudentID; 
        //if string password(HashedPassword)  matches stored hash(student.Passowrd) return student list 


        //else return a message saying login failed 
    }

Answer 1

“Cannot be used like a method” is likely because you added brackets: result.Password() if it is a property drop the brackets result.Password. Adding the brackets makes the compiler attempt to compile it as a method call when in fact it is a property or field.

The second error is you are trying to return students, which is a list of students. The method requires a string as a return value. Did you mean to instead return result.StudentID;? The exception is detailing the failed attempt at compiling the cast from List<Student> to string.

I cannot offer any advice on the second half of your questions.

Update

You are expected to find a method called SequenceEqual on byte[]. This is a Linq extension method so you may need to add:

using System.Linq;

To the top of your file.

You will then likely get an error trying to pass a string to this method: SequenceEqual(result.Password);.