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c#linqdictionarylambda
Hussein Salman
Hussein Salman

Reputation: 8246

Querying C# Dictionary using Lambda expressions

Let' say I have this Declared Dictionary:

 private static Dictionary<int, List<Models.APIAccessControl>> _APIRights = GetAPIRights();

Where the key represents the roleId, the value represent the class:

 public class APIAccessControl
{
    public APIControllerRoute ControllerRoute { get; set; }
    public APIActionRoute ActionRoute { get; set; }
    public bool IsAuthorized { get; set; }

}

I am trying to check if the user is authorized to access this api. My idea is to query the dictionary and get all list of APIAccessControl for the roles, then query those APIAccessControl lists for the APIActionRoute he is trying to navigate:

I got the Dictionary Values that contain those list for the roles i want, but how to cast a List of Values to List and make this query:

public static bool CanAccess(int[] roleIDs, APIActionRoute apiActionRoute)
   {
            bool canAccess = false;

            var apiAccessList = _APIRights.Where(x => roleIDs.Contains(x.Key)).Select(x => new { x.Value}).ToList();

      //Querying to get all List<Models.APIAccessControl> that has any matchig   APIActionRoute
    }

Upvotes: 0

Views: 15984

Answers (4)

Paul Tsai
Paul Tsai

Reputation: 903

I think the SelectMany may help.

public static bool CanAccess(int[] roleIDs, APIActionRoute apiActionRoute)
{
    return _APIRights.Where(x => roleIDs.Contains(x.Key))
        .SelectMany(x => x.Value)
        .Any(a => a.ActionRoute == apiActionRoute);
}

Upvotes: 0

Patrick Huizinga
Patrick Huizinga

Reputation: 1340

You can modify the Select clause to give you the list you want:

var apiAccessList = _APIRights.Where(x => roleIDs.Contains(x.Key))
    .SelectMany(x => x.Value).ToList();

By not selecting to an anonymous class and by using the SelectMany, the list will be of type Models.APIAccessControl

Upvotes: 1

Dave Cousineau
Dave Cousineau

Reputation: 13198

It sounds like you want SelectMany, which projects a "list of lists" into a single list:

var apiAccessList =
   _APIRights
   .Where(x => roleIDs.Contains(x.Key))
   .SelectMany(x => x.Value)
   .ToList();

You will then have every APIAccessControl object in one big list. It would no longer be grouped by roleID though. It might also have duplicates, which may or may not matter.

Upvotes: 1

juharr
juharr

Reputation: 32296

It would be better to iterate over the role ids first to take advantage of the Dictionaries lookup.

bool canAccess = false;
foreach(var roleId in roleIDs)
{
    List<Models.APIAccessControl> controls;
    if(_APIRights.TryGetValue(roleId, out controls))
    {
        canAccess = controls.Any(control => control.ActionRoute.Equals(apiActionRoute));
        if(canAccess)
            break;
    }
}

You'll have to make sure Equals actually does the type of comparison that you desire. By default it will be a reference equality, and you'd have to overload it inside of APIActionRoute if you want value equality, or use a comparison of the desired properties instead.

A completely Linq version is a little bit messy

List<Models.APIAccessControl> controls;
bool canAccess = roleIDs.Any(
    r => _APIRights.TryGetValue(r, out controls) 
          && controls.Any(
              control => control.ActionRoute.Equals(apiActionRoute)));

Upvotes: 1

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