如何设置条件C＃if语句和LINQ where语句？

Question

The details of my situation: If a user has permissions to view a certain location's items, I need the query to select items that have a facility that matches the permissions the user has. A user might have permissions to multiple facilities. There may be a user that has access to LOC1, LOC2 and also LOC3. There may be a user with only access to LOC1. I might be overlooking something extremely simple to solve this.

if(System.Web.HttpContext.Current.User.IsInRole("App_Inventory_LOC1_Access")) 
{
    items = items.Where(s => s.Facility == "LOC1");
}

if(System.Web.HttpContext.Current.User.IsInRole("App_Inventory_LOC2_Access")) 
{
    items = items.Where(s => s.Facility == "LOC2");
}

if(System.Web.HttpContext.Current.User.IsInRole("App_Inventory_LOC3_Access")) 
{
    items = items.Where(s => s.Facility == "LOC3");
}

Answer 1

So you just construct a list of allowed facilities, and then check if s.Facility is in those:

var facilities = new List<string>();
if(System.Web.HttpContext.Current.User.IsInRole("App_Inventory_LOC1_Access")) 
{
    facilities.Add("LOC1");
}
// same for other facilities
// ...

items = items.Where(s => facilities.Contains(s.Facility));

To further simplify it, you could group roles and facilities in some kind of map, and iterate through that - will make it much easier to add new facilities for example.

Answer 2

You can refactor that with a dictionary to map user role to facility:

var userFacilityMapping = new Dictionary<string, string>
{
    ["App_Inventory_LOC1_Access"] = "LOC1",
    ["App_Inventory_LOC2_Access"] = "LOC2",
    ["App_Inventory_LOC3_Access"] = "LOC3",
};
var userFacilities = userFacilityMapping
    .Where(x => HttpContext.Current.User.IsInRole(x.Key))
    .Select(x => x.Value)
    .ToArray();

items = items.Where(x => userFacilities.Contains(x.Facility));

Answer 3

I think you're overwriting your result set. Say if you have access to LOC1 and LOC3, it will first choose all the LOC1 items, and then from the LOC1 items it will choose the LOC3 items which is empty.

You want to only filter the original item set. Something like

var results = new List<Item>();

if(System.Web.HttpContext.Current.User.IsInRole("App_Inventory_LOC1_Access")) 
{
    results.AddRange(items.Where(s => s.Facility == "LOC1"));
}

if(System.Web.HttpContext.Current.User.IsInRole("App_Inventory_LOC2_Access")) 
{
    results.AddRange(items.Where(s => s.Facility == "LOC2"));
}

if(System.Web.HttpContext.Current.User.IsInRole("App_Inventory_LOC3_Access")) 
{
    results.AddRange(items.Where(s => s.Facility == "LOC3"));
}