Question

I have following code that checks whether userRoles collection has any of the values in authorizedRolesList. It does not work if the userRoleName has a whitespace.

What is the most efficient LINQ way for handling this?

CODE

        List<string> authorizedRolesList = null;
        string AuthorizedRolesValues = "A, B ,C,D";
        if (!String.IsNullOrEmpty(AuthorizedRolesValues))
        {
            authorizedRolesList = new List<string>((AuthorizedRolesValues).Split(','));
        }

        string userRoleName = String.Empty;

        Collection<string> userRoles = new Collection<string>();
        userRoles.Add("B   ");

        bool isAuthorizedRole = false;
        if (userRoles != null)
        {
            foreach (string roleName in userRoles)
            {
                userRoleName = roleName.Trim();
                if (authorizedRolesList != null)
                {
                    //Contains Check
                    if (authorizedRolesList.Contains(userRoleName))
                    {
                        isAuthorizedRole = true;
                    }
                }

            }
        }

REFERENCE:

1. When to use .First and when to use .FirstOrDefault with LINQ?
2. Intersect with a custom IEqualityComparer using Linq
3. Ignoring hyphen in case insensitive dictionary keys
4. C#: splitting a string and not returning empty string
5. When does IEnumerable.Any(Func) return a value?
6. Is IEnumerable.Any faster than a for loop with a break?

Answer 1

I guess most efficient LINQ way means most readable here.

The obvious way is to use StringSplitOptions.RemoveEmptyEntries when calling Split() and not storing the whitespace in the first place.

authorizedRolesList = AuthorizedRolesValues.Split(new []{','}, StringSplitOptions.RemoveEmptyEntries);

---

But if for some reason you want to keep the additional whitespace or can’t change the entries in authorizedRolesList, you can easily change your if clause from

if (authorizedRolesList.Contains(userRoleName))

to

if (authorizedRolesList.Any(x => x.Trim() == userRoleName))

---

BTW, talking about LINQ:

You could just replace your code with

bool isAuthorizedRole = userRoles.Any(ur => authorizedRolesList.Any(ar => ar.Trim() == ur.Trim()))

if you ensure userRoles and authorizedRolesList are not null (use an empty collection instead).

Even more readable IMHO would be something like

bool isAuthorizedRole = userRoles.Intersect(authorizedRolesList, new IgnoreWhitespaceStringComparer()).Any();

where IgnoreWhitespaceStringComparer would look like

class IgnoreWhitespaceStringComparer : IEqualityComparer<string>
{
    public bool Equals(string x, string y)
    {
        return x.Trim().Equals(y.Trim());
    }

    public int GetHashCode(string obj)
    {
        return obj.Trim().GetHashCode();
    }
}