I am trying to store list of products in List<> which I have stored in session, but when I add second product it only shows first in my View page.
..............
List<ShoppingCartItem> ShoppingCartItems = new List<ShoppingCartItem>
{
new ShoppingCartItem() {Product = product.Name, Attributes = atts, Options = opts, Price = producttotalprice, Quantity = 1}
};
if (Session["Cart"] == null)
{
Session["Cart"] = ShoppingCartItems;
}
return View(Session["Cart"]);
}
Anybody can help me please to retrieve all products I have stored.
You're creating a new List<ShoppingCartItem> every time and only ever putting one element in that list. It sounds like you want to first check if there's already a list in the session. And, if so, add the new element to that list. Something like this:
List<ShoppingCartItem> shoppingCartItems;
if (Session["Cart"] != null)
{
shoppingCartItems = (List<ShoppingCartItem>)Session["Cart"];
}
else
{
shoppingCartItems = new List<ShoppingCartItem>();
}
shoppingCartItems.Add(new ShoppingCartItem() {Product = product.Name, Attributes = atts, Options = opts, Price = producttotalprice, Quantity = 1});
Session["Cart"] = shoppingCartItems;
return View(shoppingCartItems);
If that is the "add" code, you're not actually amending the list. You're declaring an entirely new ShoppingCartItems list which contains the new product.
It works for the first product because this returns true:
if (Session["Cart"] == null)
The second time around this is false, and nothing happens. What you want to do is:
1) Retrieve the session cart which is a 'List' (if it is null, then initialise a new one.
2) Create a new ShoppingCartItem from the product which has been passed to the controller. Add that product to the cart.
Related
for (int i = 0; i < skus.Count; i++)
{
sku item = new sku();
item = skus[i];
sku sku = CompanyDbContext.skus.Where(s => s.item_no == item.item_no).FirstOrDefault();
if (sku == null) // ok to insert [no duplicate item numbers]
{
CompanyDbContext.skus.Add(item);
}
}
CompanyDbContext.SaveChanges();
I'm getting
collection was modified enumeration operation may not execute
error. How can I fix this ?
As mentioned in the comments, this happens because you are modifying the collection which you are looping through as you're performing your work.
One option you have is to create a temporary collection and add your sku items to that, and finally add the contents of the temporary List<sku> to your CompanyDbContext
// Create a new temporary list
List<sku> tempSkus = new List<sku>();
for (int i = 0; i < skus.Count; i++)
{
// Let's assign item to skus[i] immediately, we don't need a new instance here when we're later re-pointing to an existing instance
sku item = skus[i];
// Use LINQ Any function to determine whether there are any existing SKU's already
bool existingSku = CompanyDbContext.skus.Any(s => s.item_no == item.item_no);
// There are no duplicates, let's add this sku item to our temporary List
if(!existingSku)
{
tempSkus.Add(item);
}
}
// Add the Range of tempSkus List to the CompanyDbContext
CompanyDbContext.skus.AddRange(tempSkus);
CompanyDbContext.SaveChanges();
Or if you prefer LINQ
// Create a new temporary list
List<sku> tempSkus = skus.Where(p => CompanyDbContext.skus.Any(s => s.item_no != p.item_no)).ToList();
// Add the Range of tempSkus List to the CompanyDbContext
CompanyDbContext.skus.AddRange(tempSkus);
CompanyDbContext.SaveChanges();
The problem is that you are modify the same thing that you are iterating. As best practice you should update your method something like this:
//get search predicat from List<sku> skus
var item_nos = skus.Select(s=>s.item_no).ToList();
//items already in repo
var addedItems = CompanyDbContext.skus.Where(s => item_nos.Contains(s.item_no)).ToList();
var newItems = skus.Except(addedItems).ToList();
foreach(var sku in newItems){
CompanyDbContext.skus.Add(item);
}
CompanyDbContext.SaveChanges();
Few days back I put a question regarding mapping two classes Message and MessageStatusHistory using EF. The mapping is going fine but I am facing some problems with the navigation property StatusHistory in class Message that relates it to MessageStatusHistory objects. I am loading the messages for one user only and want to the statuses pertaining to that user only. Like I would want to show if the user has marked message as read/not-read and when. If I use default loading mechanism like following it loads all the history related to the message irrespective of the user:
IDbSet<Message> dbs = _repo.DbSet;
dbs.Include("StatusHistory").Where(x=>x.MessageIdentifier == msgIdentifier);
To filter history for one user only I tried following trick:
IDbSet<Message> dbs = _repo.DbSet;
var q = from m in dbs.Include("StatusHistory")
where m.MessageIdentifier == msgIdentifier
select new Message
{
MessageIdentifier = m.MessageIdentifier,
/*OTHER PROPERTIES*/
StatusHistory = m.StatusHistory
.Where(x => x.UserId == userId).ToList()
};
return q.ToList();//THROWING ERROR ON THIS LINE
I am getting the error:
The entity or complex type 'MyLib.Biz.Message' cannot be constructed in a LINQ
to Entities query.
I have tried by commenting StatusHistory = m.StatusHistory.Where(x => x.UserId == userId).ToList() also but it has not helped.
Please help me in getting Messages with filtered StatusHistory.
EDIT:- above is resolved with this code:
var q = from m in _repository.DBSet.Include("Histories")
where m.MessageIdentifier == id
select new {
m.Id,/*OTHER PROPERTIES*/
Histories = m.Histories.Where(x =>
x.SenderId == userId).ToList()
};
var lst = q.ToList();
return lst.Select(m => new Message{
Id = m.Id, MessageIdentifier = m.MessageIdentifier,
MessageText = m.MessageText, Replies = m.Replies,
ReplyTo = m.ReplyTo, Histories = m.Histories, SenderId =
m.SenderId, SenderName = m.SenderName, CreatedOn = m.CreatedOn
}).ToList();
But if I try to include replies to the message with:
from m in _repository.DBSet.Include("Replies").Include("Histories")
I am getting error on converting query to List with q.ToList() for Histories = m.Histories.Where(x=> x.SenderId == userId).ToList().
About your EDIT part: You cannot use ToList() in a projection, just leave it an IEnumerable<T> and convert to a List<T> when you construct the Message. You also don't need to create two list objects, you can switch from the LINQ to Entities query to LINQ to Objects (the second Select) by using AsEnumerable():
var list = (from m in _repository.DBSet
where m.MessageIdentifier == id
select new {
// ...
Histories = m.Histories.Where(x => x.SenderId == userId)
})
.AsEnumerable() // database query is executed here
.Select(m => new Message {
// ...
Histories = m.Histories.ToList(),
// ...
}).ToList();
return list;
Be aware that Include has no effect when you use a projection with select. You need to make the properties that you want to include part of the projection - as you already did with select new { Histories.....
Hi i'm looking for some help in how to append rows to an existing LINQ object. In the controller method below I have two result sets, i'm looping the Sites and want to add a record to the 'results' object for each record in the Sites object.
I've tried concat etc but not getting anywhere, just need s small example to assist, many thanks in advance, J
public IQueryable<UsersToSite> FindAllUsersToSites(int userId,SystemType obj)
{
var results = (from usersToSite in this._db.UsersToSites
where usersToSite.UserId == userId &&
usersToSite.SystemTypeId == obj
orderby usersToSite.Site.SiteDescription
select usersToSite);
// Now for each remaining Site append a record thats not physically in the database. From the view the user will be able to click these records to ADD new
// I'll then build in a search
var sites = (from site in this._db.Sites
where !(from o in _db.UsersToSites where (o.UserId == userId && o.SystemTypeId == obj) select o.SiteId).Contains(site.SiteId)
orderby site.SiteDescription
select site);
foreach (var site in sites)
{
// HERE I want to create the new ROW in results object
//results = new[results] { new { UsersToSiteId = null, AccessTypeId = null } }.Concat(sites);
//SiteId=site.SiteId,
//UsersToSiteId = 0,
//AccessTypeId = 0,
//UserId = userId
}
return results;
}
I don't think you can, if you want to have keep queryable.
However, if you materialize the results with ToList(), then you can:
var sites = (from site in this._db.Sites
where !(from o in _db.UsersToSites where (o.UserId == userId && o.SystemTypeId == obj) select o.SiteId).Contains(site.SiteId)
orderby site.SiteDescription
select site)
.ToList();
sites.Add(new Site { UsersToSiteId = null, etc });
If it was LINQ to Objects, you could do Concat.
The problem here that it can't do ConcatLINQ query that will have one part from SQL and another from objects. You need to materialize results first and then concat to object.
I am working in MVC2. Here i had Employee Screen. There itself i am having a dropdown list. In that all the Employee Names will loaded. The Employee profile which i am viewing should not be loaded in the dropdown list. I should remove the particular Employee from the dropdown list. Here is my code for loading dropdown...How to do this...
Dictionary<string, Employee> Employee1 = new Dictionary<string, EmployeeDetails>();
Employee1 = EmployeeProxy.GetPrimaryEmployeeList(UserIdentity.TenantID);
List<EmployeeDetails> managerDetailsList = Employee1.Values.ToList();
if (managerDetailsList != null && managerDetailsList.Count > 0)
{
managerDetailsList.Sort(delegate(EmployeeDetails p1, EmployeeDetails p2) { return p1.FirstName.CompareTo(p2.FirstName); });
}
foreach (EmployeeDetails employeedetails in managerDetailsList)
{
employeedetails.FirstName = employeedetails.FirstName + " " + employeedetails.LastName;
}
RobinHood,
Simply change this line:
List<EmployeeDetails> managerDetailsList = Employee1.Values.ToList();
to:
List<EmployeeDetails> managerDetailsList = Employee1.Values.Where(x => x.ID != Employee1.ID).ToList();
assuming that such an attribute (ID) exists. Basically, what i'm saying is that from the managerDetailsList, exclude the Employee1 member (based on the assumption that Employee1.Values is IQueryable).
I'm trying to do something similar to this post where I don't pull back all columns from a particular entity, however my framework makes use of inheritence and I lose scope of the entity type after it's been cast to an anonymous type.
The structure of my Entity Framework has a base entity called Action. From here I've created two inherited entities called Event and Activity. I want to pull back the last X Actions and pass them to my strongly typed view which accepts an Action and from there determines if its an Activity or Event and renders the correct partial view.
if(Model.GetType() == typeof(Event))
{
//render Event view
}
else if(Model.GetType() == typeof(Activity))
{
//render Activity view
}
I can pull the last 10 as an anonymous type and then cast:
var result = from a in new DataContext().Actions
where a.UserId == someGuidValue
select new { a.CreatedOn, a.Summary };
List<Action> list = result.AsEnumerable()
.Select(o => new Action {
CreatedOn = o.CreatedOn,
Summary = o.Summary
}).ToList();
However, once I pass the new List of Actions to my strongly typed view it loses scope of whether it's an Activity or an Event since it's been cast as an Action. My question is, without exposing the discriminator column, is there any way to cast each item to the proper type or am I going about this the wrong way?
A bit kludgy, but will work:
var result = from a in new DataContext().Actions
where a.UserId == someGuidValue
let IsEvent = a as Event != null
select new { a.CreatedOn, IsEvent, a.Summary };
List<Action> list = result.AsEnumerable()
.Select(o => o.IsEvent ?
(Action) new Event {
CreatedOn = o.CreatedOn,
Summary = o.Summary
}
: (Action) new Activity {
CreatedOn = o.CreatedOn,
Summary = o.Summary
}
}).ToList();
Example with type-specific columns, presuming that e.EventSpecific is of a nullable type.
var result = from a in new DataContext().Actions
where a.UserId == someGuidValue
let ev = a as Event
let IsEvent = ev != null
select new { a.CreatedOn, IsEvent, a.Summary, ev.EventSpecific };
List<Action> list = result.AsEnumerable()
.Select(o => o.IsEvent ?
(Action) new Event {
CreatedOn = o.CreatedOn,
Summary = o.Summary,
EventSpecific = o.EventSpecific
}
: (Action) new Activity {
CreatedOn = o.CreatedOn,
Summary = o.Summary,
EventSpecific = o.EventSpecific // will be null, but using o.EventSpecific saves casting
}
}).ToList();
If o.EventSpecific is of a non-nullable type, then you must convert it to a nullable type in the L2E query.
You are probably on the wrong way. At first I would assume that Action should be an abstract class and you should not be able to create instances of it at all. If you then only fetch a subset of the properties and the subset does no longer allow to discriminate between events and activities, it is probably the wrong way to try making events and activities out of them.
So it actually seems not to be a technical problem - it should be quite easy to include some discrimination information in the anonymous type - but a design problem. I suggest to rethink if it is required to discriminate the query result and if so if it is really a good idea to discriminate the result in absence of an discriminator.