How to use multi-valued/array parameter(enum values) obtained from Request.Query in LINQ queries?

Question

I'm still new to modern styles .NET development and Entity Framework. I'm trying to get a list of objects where one of the values falls in a list of other values, and I'm trying to use the LINQ query methods to do so.

string cb_orderstatus = Request.Query["OrderStatusSearch"].ToString();
if (!string.IsNullOrEmpty(cb_orderstatus))
{
    string[] orderStatuses = cb_orderstatus.Split(",");
    query = query.Where(o => orderStatuses.Contains(o.Status.ToString()));
}

If the value of the cb_orderstatus is a string array containing 5, 10, and 15, I want the query to return objects where their Status equals any of these values. Currently it is not working. Can anyone help?

Also, what does it mean not working? Does it throw an exception, what kind of exception or what kind of result it returns? — OlegI, Nov 27 '19 at 18:12
Your code appears to be logically correct. My educated guess is that the result of `o.Status.ToString()` is not what you expect or if it is, there is a problem with the string comparison. — JuanR, Nov 27 '19 at 18:13
If `Request.Query["OrderStatusSearch"]` is an array then the result of `ToString` is not going to be a comma separated list of the values. It's going to be the type of the array like `"System.Int32[]"` for a `int[]` — juharr, Nov 27 '19 at 18:14
if you could provide us with code we can reproduce, that would be helpful — Casey Crookston, Nov 27 '19 at 18:15
I was hired to edit existing code, so there is a lot of code that I am dealing with that I did not write. I'm doing my best to understand it. o.Status is an OrderStatus enum. query is an IQueryable defined earlier in the code as: ``` var query = _db.Orders.AsNoTracking(); ``` _db is a DbContext. The URL is being requested with Search?OrderStatus=0&OrderStatusSearch2=10 and I have a property on the model class that has [BindProperty] on it and is of type List but it is not being populated with any data. — Mike Payne, Nov 27 '19 at 18:46
There were line breaks in the above reply but they're not being properly displayed. :( I'm new to posting on StackOverflow and I haven't had the easiest time learning it, especially since it keeps telling me that I am banned from posting because my questions "have not been well received by the community." — Mike Payne, Nov 27 '19 at 18:48

Eugene Podskal · Answer 1 · 2019-11-27T20:23:45.170

It is an educated guess, but as you say that

o.Status is an OrderStatus enum

then most probably you need to convert values from cb_orderstatus to actual OrderStatuses values and use OrderStatus[].Contains in the query

string cb_orderstatus = Request.Query["OrderStatusSearch"].ToString();
if (!string.IsNullOrEmpty(cb_orderstatus))
{
    var orderStatuses = cb_orderstatus
        .Split(",")
        .Select(statusIntegerString => 
            (OrderStatus)int.Parse(statusIntegerString))
        .ToArray();
    query = query.Where(o => orderStatuses.Contains(o.Status));
}

Though I am not sure that you will get comma-separated values from Request.Query["OrderStatusSearch"].

In any case, it would be orders of magnitude better to rely on standard parameter binding, so I'd recommend you to post another question that deals with

I have a property on the model class that has [BindProperty] on it and is of type List but it is not being populated with any data.

How to use multi-valued/array parameter(enum values) obtained from Request.Query in LINQ queries?

1 Answers1