Question

I have method where I need to retrieve using EF the last ten entries in the database and check to see if there is a match between the value and the current term. Here is what I have thus far

public static int ValidatePassword(string username, string password, int securityUserId)
        {
                int validResult = 0;
                /*Need to pass to client a value based upon success or failure of validation
                 * 0 - success
                 * 1 - password has already been used in the last 10 entries
                 * 2 - password does not meet CJIS requirements
                 */
                IEnumerable<string> oldpassword = null;
                // Create a Regular Expression to determine whether or not special characters are present.
                Regex regularExpression = new Regex("[^a-z0-9]");

                //if id exists pull last ten passwords
                if (securityUserId > 0)
                {
                    long id = Convert.ToInt64(securityUserId);

                    using (var context = new SecurityEntities(string.Empty))
                    {
                        try
                        {
                            oldpassword = (from p in context.SecurityAudits
                                           where p.SecurityUserId == id &&
                                           p.OldPassword == password
                                           orderby p.ActionDate descending
                                           select p.OldPassword.Take(10).ToString()).ToList();
                        }
                        catch (Exception ex)
                        {
                            string err = string.Format("ValidateCJISPassword() was unable to return an object msg:{0}", ex.Message);
                            throw new Exception(err, ex.InnerException);
                        }
                        finally
                        {
                            context.Dispose();
                        }
                    }
                }

                else if (oldpassword == null)
                {
                    //no matching record found now check other requirements
                    if ((password.Length >= DEFAULT_CJIS_PASSWORD_MIN_LENGTH) && regularExpression.IsMatch(password) && (password != username))
                    {
                        //success
                        validResult = 0;
                    }
                    else
                    {
                        //password does not meet standard CJIS requirements
                        validResult = 2;
                    }
                }
                else
                {
                    //matching record was found
                    validResult = 1;
                }
                return validResult;
            }
}

Where I am currently hung up is the query throws an exception on the ToString() method

LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression.

I’m still learning EF and how linq works so I’m not sure what the best approach here is. Should I try to set the result to something other than IEnumerable like an array or List or is there another approach I should consider?

Thanks in advance,

Cheers,

Answer 1

Change this

oldpassword = (from p in context.SecurityAudits
                   where p.SecurityUserId == id &&
                   p.OldPassword == password
                   orderby p.ActionDate descending
                   select p.OldPassword.Take(10).ToString()).ToList();

To this

oldpassword = (from p in context.SecurityAudits
               where p.SecurityUserId == id &&
               p.OldPassword == password
               orderby p.ActionDate descending
               select p.OldPassword).Take(10).ToList();

The problem was that your Take(10) clause was not part of the whole result but inside the actual linq statement.. it goes on the outside of it to take the top 10 of the entire resultset.. then you do the ToList() which turns the whole thing into an array

The next problem is that you just created an array and assigned it to oldpassword

I don’t see anything here that does anything with the array…

You need to do something like:

1. declare your array of strings
2. assign the array to the return of the linq query
3. evaluate the return for > 0 results
4. if > 0 then the password has been used in the last 10
5. if = 0 then new password should be ok, correct?