Using VBNET, MVC 3 and Entity Framework to write my first mvc application - a single user blog application. I am trying to create an archive sidebar that will render something like October 2011 and when the user clicks they will see all posts in october. Right now all my attempts show either duplicate dates - if there are 3 posts in october then i see october 2011 3 times or i only get back one month year combo say oct 2011.
Using groupby with firstordefault i only get back one month yaear combo.
posts = _rdsqlconn.Posts.Where(Function(p) p.PostIsPublished = True).GroupBy(Function(d) d.PostDatePublished).FirstOrDefault
How can i get back unique month year combos with EF?
Additional info
I have that function in my repository. I want to pull the month and year pairs so that i have only one pair for say ocotober even if there are 3 posts in october.
In the repository:
Public Function SelectPostsByDate() As IEnumerable(Of Entities.Post) Implements Interfaces.IPostRepository.SelectPostsByDate
Using _rdsqlconn As New RDSQLConn
Dim posts
posts = _rdsqlconn.Posts.Where(Function(p) p.PostIsPublished = True).GroupBy(Function(p) New With {p.PostDateCreated.Year, p.PostDateCreated.Month}).Select(Function(g) g.Key)
'posts = _rdsqlconn.Posts.Where(Function(p) p.PostIsPublished = True).GroupBy(Function(p) New With {p.PostDatePublished.Value.Year, p.PostDatePublished.Value.Month})
Return posts
End Using
End Function
In my controller i have
Function DateViewPartial() As PartialViewResult
Return PartialView(_postRepository.SelectPostsByDate)
End Function
My partial view has:
#ModelType IEnumerable (of RiderDesignMvcBlog.Core.Entities.Post)
<hr />
<ul style="list-style: none; margin-left:-35px;">
#For Each item In Model
#<li> #Html.ActionLink(item.PostDatePublished.Value.ToString("Y"), "Archives", "Blog", New With {.year = item.PostDatePublished.Value.Year, .month = item.PostDatePublished.Value.Month}, Nothing)</li>
Next
</ul>
In _Layout.vbhtml i call the partial view to render in the sidebar:
<h3>Posts by Date</h3>
#code
Html.RenderAction("DateViewPartial", "Blog")
End Code
I would try this (in C#):
var yearMonths = _rdsqlconn.Posts
.Where(p => p.PostIsPublished)
.GroupBy(p => new { p.PostDatePublished.Year, p.PostDatePublished.Month })
.Select(a => a.Key)
.ToList();
It gives you a list of anonymous objects. Each object has a Year and a Month property - for instance yearMonths[0].Year and yearMonths[0].Month, etc. By applying the Select you actually throw away the elements in each group and you get only a list of group keys (year and month).
Edit
I think, for your purpose the best way is to introduce a "ViewModel" for your sidebar partial view. The ViewModel would describe the year and month group, for instance:
public class ArchiveMonthViewModel
{
public int Year { get; set; }
public int Month { get; set; }
}
Then you don't group with an anonymous type but use this ViewModel type:
var archiveViewModels = _rdsqlconn.Posts
.Where(p => p.PostIsPublished)
.GroupBy(p => new ArchiveMonthViewModel
{
Year = p.PostDatePublished.Year,
Month = p.PostDatePublished.Month
})
.Select(a => a.Key)
.ToList();
archiveViewModels is now a named type: List<ArchiveMonthViewModel> which you can return from your method:
public IEnumerable<ArchiveMonthViewModel> SelectPostsByDate()
{
// code above ...
return archiveViewModels;
}
Now your partial view should be based on a model of type IEnumerable<ArchiveMonthViewModel> (and not IEnumerable<Post>). In your foreach loop (#For Each item In Model) you pull out the ArchiveMonthViewModel elements which are the item in the loop now and then create the action link using item.Year and item.Month.
(Hopefully you can translate this sketch into VB.)
In VB:
Dim groupedPosts = _rdsqlcon.Posts.
Where(Function(p) p.PostIsPublished = True).
GroupBy(Function(p) New With {p.PostDatePublished.Year, p.PostDatePublished.Month }).
Select(g => g.Key)
This just returns the unique Years and Months. If you want to include the Posts for each, try the following:
Dim groupedPosts = _rdsqlcon.Posts.
Where(Function(p) p.PostIsPublished = True).
GroupBy(Function(p) New With {p.PostDatePublished.Year, p.PostDatePublished.Month
From there, you can show the year/month groupings and the associated posts for each:
For Each group In groupedPosts
Console.WriteLine(group.Key.Year & "-" & group.Key.Month)
For Each post In group
Console.WriteLine(post.PostDatePublished)
Next
Next
Related
I have an ASP.NET MVC app using Entity Framework from our SQL Server backend.
Goal is to create ~18 WPackage entries via a foreach loop:
foreach (var dbitem in dbCList)
The code works for a single WPackage entry, but we have a request from the customer to create 300+ WPackages, so trying to use the Entity Framework code for a single "Add" and loop to create 300+ adds.
The T-SQL would be very challenging as there are many keys created on the fly/at row creation, so for activities >> resources, we'd have to insert the activity, grab or remember the activity key, then add resources with that newly created activity key.
Each WPackage (this is the main parent table) could have one or more of the following child table entries:
1+ activities
each activity would have 1+ resource
1+ budgets
1+ Signatures
1+ CostCodes
Our schema or model diagram would be:
WPackage
--Activities
-----Resources (child of Activities)
--CostCodes
--Budgets
--Signatures
The following code fails on:
dbContextTransaction.Commit();
with an error:
The transaction operation cannot be performed because there are pending requests working on this transaction.
[HttpPost]
public ActionResult Copy([Bind(Include = "ID,WBSID,...***fields excluded for brevity")] Package model)
{
if (ModelState.IsValid)
{
try
{
using (var dbContextTransaction = db.Database.BeginTransaction())
{
var dbCList = db.Packages.Join(db.WBS,
*expression omitted for brevity*)
// this dbClist will build about 18 items in the collection for below loop
foreach (var dbitem in dbCList)
{
int testWPID = dbitem;
WPackage prvWP = db.WPackages.Find(dbitem);
int previousWPID = dbitem;
WPackage previousWP = db.WPackages.Find(dbitem);
model.ID = dbitem;
db.WPackages.Add(model);
db.SaveChanges();
var budgets = db.Budgets.Where(i => i.WPID == previousWPID);
foreach (Budget budget in budgets)
{
budget.WPID = model.ID;
db.Budgets.Add(budget);
}
var costCodes = db.CostCodes.Where(i => i.WPID == previousWPID);
foreach (CostCode costCode in costCodes)
{
costCode.WPID = model.ID;
db.CostCodes.Add(costCode);
}
var activities = db.Activities.Where(i => i.WPID == previousWPID);
// *code excluded for brevity*
var previousActivityID = activity.ID;
db.Activities.Add(activity);
db.SaveChanges();
var resources = db.Resources.Where(i => i.ActivityID == previousActivityID);
foreach (Resource resource in resources)
{
resource.WPID = model.ID;
resource.ActivityID = activity.ID;
resource.ActivityNumber = activity.ActivityNumber;
db.Resources.Add(resource);
db.SaveChanges();
}
}
var signatures = db.RolesAndSigs
.Where(i => i.KeyId == previousWPID && i.Type == "WPL")
.OrderBy(i => i.Role)
.OrderBy(i => i.Person);
foreach (RolesAndSig signature in signatures)
{
db.RolesAndSigss.Add(signature);
}
db.SaveChanges();
dbContextTransaction.Commit();
}
}
}
}
I've also tried to have the Commit() run outside the foreach dbitem loop like:
db.SaveChanges();
//dbContextTransaction.Commit();
}
dbContextTransaction.Commit();
...but this returns error of:
[EXCEPTION] The property 'ID' is part of the object's key information and cannot be modified.
The code you posted has some issues that don't make sense, and probably aren't doing what you think they are doing. The crux of the issue you are facing is that Entity Framework tracks all references to entities it loads and associates:
Firstly this code:
int testWPID = dbitem;
WPackage prvWP = db.WPackages.Find(dbitem);
int previousWPID = dbitem;
WPackage previousWP = db.WPackages.Find(dbitem);
prvWP and previousWP will be pointing to the exact same reference, not two copies of the same entity. Be careful when updating either or any other reference retrieved or associated with that same ID. They all point to the same instance. If you do want a stand-alone snaphot reference you can use AsNoTracking().
Next, when you do something like this in a loop:
model.ID = dbitem;
db.WPackages.Add(model);
In the first iteration, "model" is not an entity. It is a deserialized block of data with the Type of the Package entity. As soon as you call .Add(model) that reference will now be pointing to a newly tracked entity reference. In the next loop you are telling EF to change that tracked entity reference's ID to a new value, and that is illegal.
What it looks like you want to do is create a copy of this model for each of the 18 expected iterations. For that what you want to do would be something more like:
foreach (var dbitem in dbCList)
{
var newModel = new WPackage
{
ID = dbItem,
WBSID = model.WBSID,
/// copy across all relevant fields from the passed in model.
};
db.WPackages.Add(newModel);
// ...
}
It would be quite worthwhile to leverage navigation properties for the related entities rather than using explicit joins and trying to scope everything in an explicit transaction with multiple SaveChanges() calls. EF can manage all of the FKs automatically rather than essentially using it as a wrapper for individual ADO CRUD operations.
You will need to be explicit between when you want to "clone" an object reference vs. "copy" a reference. For example, if I have a Customer that has an Address, and Addresses have a Country reference, when I clone a Customer, I will want to clone a new Address record for that Customer, however ensure that the Country reference is copied across. If I have a record for Jack at an 123 Apple Street, London in England, and go to clone Jack to make a record for Jill at the same address, they might be at the same location now, but not always, so I want them to point at different Address records in case Jill moves out. Still, there should only be one record for "England". (Jill may move to a different country, but her address record would just point at a different Country Id)
Wrong:
var jill = context.Customers.Single(c => c.Name == "Jack");
jill.Name = "Jill";
context.Customers.Add(jill);
This would attempt to rename Jack into Jill, then "Add" the already tracked instance, resulting in an exception.
Will work, but still Wrong:
var jack = context.Customers.AsNoTracking().Single(c => c.Name == "Jack");
var jill = jack;
jill.Name = "Jill";
context.Customers.Add(jill);
This would technically work by loading Jack as an untracked entity, and would save Jill as a new record with a new Id. However this is potentially very confusing. Depending on how the AddressId/Address is referenced we could end up with Jack and Jill referencing the same single Address record. Bad if you want Jack and Jill to have different addresses.
Right:
var jack = context.Customers
.Include(c => c.Address)
.ThenInclude(a => a.Country)
.Single(c => c.Name == "Jack");
var jill = new Customer
{
Name = "Jill",
// copy other fields...
Address = new Address
{
StreetNumber = jack.Address.StreetNumber,
StreetName = jack.Address.StreetName,
Country = jack.Address.Country
}
};
context.Customers.Add(jill);
The first detail is to ensure when we load Jack that we eager load all of the related details we will want to clone or copy references to. We then create a new instance for Jill, copying the values from Jack, including setting up a new Address record. The Country reference is copied across as there should only be ever a single record for "England".
Edit: For something like a roll-over scenario if you have a package by year, let's use the example of a Package class below:
public class Package
{
[Key]
public int PackageId { get; set; }
[ForeignKey("PackageType")]
public int PackageTypeId { get; set; }
public int Year { get; set; }
// .. More package related details and relationships...
public virtual PackageType PackageType { get; set; }
}
A goal might be to make a new Package and related data for Year 2022 from the data from 2021, and apply any changes from a view model passed in.
Find is a poor choice for this because Find wants to locate data by PK. If you're method simply passes an entity to be copied from (I.e. the data from 2021) then this can work, however if you have modified that data from 2021 to represent values you want for 2022 that could be dangerous or misleading within the code. (We don't want to update 2021's data, we want to create a new record set for 2022) To make a new Package for 2022 we just need the updated data to make up that new item, and a way to identify a source for what to use as a template. That identification could be the PK of the row to copy from (ProductId), or derived from the data passed in. (ProductTypeId, and Year-1) In both cases if we want to consider related data with the "copy from" product then it would be prudent to eager load that related data in one query rather than going back to the database repeatedly. Find cannot accommodate that.
For instance if I want to pass data to make a new product I pass a ProductTypeId, and a Year along with any values to use for the new structure. I can attempt to get a copy of the existing year to use as a template via:
var existingProduct = context.Products
.Include(x => x.Activities) // Eager load related data.
.Include(x => x.CostCodes)
// ...
.Single(x => x.ProductTypeId == productTypeId && x.Year = year - 1);
or if I passed a ProductId: (such as if I could choose to copy the data from a selected year like 2020 instead)
var existingProduct = context.Products
.Include(x => x.Activities)
.Include(x => x.CostCodes)
// ...
.Single(x => x.ProductId == copyFromProductId);
Both of these examples expect to find one, and only one existing product. If the request comes in with values that it cannot find a row for, there would be an exception which should be handled. This would fetch all of the existing product information that we can copy from, alongside any data that was passed into the method to create a new Product.
So I was working on a DropDown list and it works, but it has many duplicate emails, I just want to see distinct emails... So I tried doing .Distinct() in the model class, but that still gave me duplicates..
Model Class:
public string One_Manager_Email{ get; set; }
public List<Hello> getManagers()
{
var que = (from wr in db.View
select new Hello
{
O_Manager_Email= wr.One_Manager_Email
}).Distinct().ToList();
return que;
}
Controller Class: (This is probably where the problem is happening)
public ActionResult Index()
{
test = new Hello();
ViewBag.Managers = new SelectList(test.getManagers(), "", "O_Manager_Email");
return View(test.getStuff());
}
View Class:
<div>
#Html.DropDownList("Managers", ViewBag.Managers as SelectList)
</div>
Any help would be great, thank you!
You need to group your objects by the property you want them to be distinct by, and then select the first element of the grouping.
public List<Hello> getManagers()
{
var que = (from wr in db.View
select new Hello
{
O_Manager_Email= wr.One_Manager_Email
})
.GroupBy(g => g.O_Manager_Email) //group by property
.Select(g => g.First()) //take first element from every grouping
.ToList();
return que;
}
For some more details, you can see this post that has more details on grouping and distinct: LINQ's Distinct() on a particular property
Distinct won't work on objects like that, as objects are always distinct, but you can try using group by in your query, something along these lines:
var que = (from wr in db.View
group new {wr.One_Manager_Email}
by new {wr.One_Manager_Email} into grouped
select new Hello
{
O_Manager_Email= grouped.Key.One_Manager_Email
}).ToList();
return que;
If you just need email address, you can select just string instead of selecting Hello object. If you select Hello object and try to distinct you like that way, you obviously get duplicated items. Because every object is already unique.
I believe you have already answer. GroupBy might solve your problem. However unless you really need GroupBy, don't use GroupBy! It's really expensive operation.
In your case, you should use DistinctBy.
var distinctList = list.DistinctBy(x => x.Prop).ToList();
On your code:
var que = (from wr in db.View
select new Hello
{
O_Manager_Email = wr.One_Manager_Email
}).DistinctBy(x=>x.O_Manager_Email).ToList();
Oh, in terms of DistinctBy usage, you should import namespace of Microsoft.Ajax.Utilities.
using Microsoft.Ajax.Utilities;
I have a database called news and have a column called description, I have two take the Last two entries from table (description column) and display the result as a single string string , ie, want to append the data in the Second last column to the last data. But I am not able to append the text,and deleted the code.
controller
public ActionResult Index()
{
var news = db.News.OrderByDescending(u => u.Id).FirstOrDefault();
return View(news);
}
view
#model Project.Models.News
<a href="#Url.Action("NewsInnerPage", "News")">
<marquee>
<p>
#Html.Raw(Model.Description)
</p>
</marquee>
</a>
sql column
I want to get the value from table last two entries as a single string . can anyone please help me to write the code . how can i append string ???
var news = db.News.OrderByDescending(u => u.Id).Take(2).ToList();
var concatenatedNews = new News {
Description = news[0].Description + news[1].Description
};
or you could do it all in one line
var news = new News { Description = string.Join("", news.OrderByDescending(u => u.Id).Take(2).Select(u => u.Description)) };
I have "Products table" with following fields
PID int,
product_name varchar(),
product_price int
"Cart table" with following fields
cart_ID
user_id
PID
So I want to display cart items of logged in user
For example if user_ID=100 is logged in , then only his cart items should be displayed to him, with all the product details.
Am using asp.net with entity framework
public ActionResult Cart()
{
Products pro = new Products();
Cart cart =new Cart();
var productID = db.cartDetails.Where(pid => pid.productId == cart.productId && cart.user_id == session["user_ID"]);
return View(db.productsDetails.Where(pid => pid.productId == productID));
}
Now problem arises, ProductID being var type I cannot compare it with pid => pid.productid.
What I want to do is first get all the product_id's of user from cart table by comparing uid_id (Logged in user) with user_id in cart table, then displaying product details of those product_id's from product Table. So obviously I need to store multiple product_id's,so that i can populate their data on the cart page.
The LINQ expression db.cartDetails.Where(pid=>pid.productId==cart.productId && cart.user_id==session["user_ID"]) would return a collection of cartDetails and not the productId. You must use select to fetch the columns you need, something like this
var productIDs = db.cartDetails
.Where(pid => pid.productId == cart.productId && cart.user_id == session["user_ID"])
.Select(cd => cd.productId)
.ToList();
This would return you a List of productIds. (If you wish to get only one productId, you could use SingleOrDefault or FirstOrDefault depending on your scenario like db.cartDetails.SingleOrDefault(pid => ...).productId).
Also note that you could have used int type for productId instead of using var if you were expecting an integer. Now you are getting a collection type IQueryable<cardDetails> being assigned to productId.
Next you cannot use an equality operator for the returned List anymore, you should check if this list contains the productId from productDetails, something like this:
return View(db.productsDetails.Where(pid => productIDs.Contains(pid.productId)));
Couldn't test this code, but the basic idea is here.
One last thing, consider using a join between the two tables: https://msdn.microsoft.com/en-us/library/bb311040.aspx
Did this and now my cart is working fine
public ActionResult Cart()
List<int> productIDs = new List<int>();
productIDs = db.cartDetails.Where(ch => ch.userId ==12).Select(cd => cd.productId).ToList() ;
List<Products> pDetails = new List<Products>();
for(int i=0;i<productIDs.Count;i++)
{
pDetails.Add(db.productsDetails.Find(productIDs[i]));
}
return View(pDetails);
I have a model , in which there's a variable
public IEnumerable<string> MonthDropDown { get; set; }
In controller , I am filling this as:
var months = "Jan,Feb,March,April,May,June,July,Aug,Sept,Oct,Nov,Dec";
ImportFiles inputfile = new AetnaCoventryMigration.Model.ImportFiles();
inputfile.MonthDropDown = months.Split(',');
In the view, I am passing a list of myModels as a model , how can I create a drop down box for this list of months? The problem is I can't use m => m.MonthDropDown as my model in view is a list of my model class.
Kindly help!
I am also using the list of models , later in my view , so cannot pass just a model to the view , I am passing Ilist<model> to the view.
Here you have 2 things:
First To edit a List of Model in a view, you can use the MVC2 way by Steven Sanderson : Editing a variable length list, ASP.NET MVC 2-style
Second to implement the dropdown: you can do something like this:
#Html.DropDownListFor(m => m.Month,
((List<string>)ViewBag.MonthDropDown).Select(option => new SelectListItem
{
Text = Html.DisplayTextFor(_ => option).ToString(),
Value = option,
Selected = (Model != null) && (option == Model.Month)
}))
In the controller, fill the Month values in a ViewBag:
var months = "Jan,Feb,March,April,May,June,July,Aug,Sept,Oct,Nov,Dec";
ViewBag.MonthDropDown = months.Split(',');