I m having a little trouble coming up with a schema to order and changing order in a article/news management system.
Here goes:
I have News Object Model as follow:
class News {
int id;
string Title;
string Content;
string OrderId;
// trimmed
}
I have CRUD for the object model. and List as follows:
Id Title Order
1. Foo -+
2. Bar -+
3. Glah -+
What i want to do is when user clicks on - for first news, i want to replace 1 and 2 orderid and of course display as well.
well how do i do this on server side? lets say for 1. item order id is 1 , how do i find the first item that has a higher order id then this one?
Or take 2. Bar, when i click on - , how do i find/replace order ids with first one. or i click on + how do i replace order id of this news with 3. Glah ?
is there a better way of doing this?
There are also some UI where user drags and drops ? any pointers on that?
When the user changes the location of an item, the server needs to know which item was changed and what it's new position is. In the code below, I'm using a List to figure out the new positons. In this sample code, newPosition is the new zero-based position and selectedArticle is the article that was moved.
List<Article> articles = LoadSortedArticles()
articles.Remove(selectedArticle);
articles.Insert(newPosition, selectedArticle);
UpdateArticles(articles);
After running, the article's index within the list tells you its new position. That applies to all articles in the list and works the same for a drag/drop UI. I don't know entity framework, but if you can map the orderId field in the database to the index of the article in the list, then you should be good to go.
I hope this is at least able to give you some ideas. Maybe someone else can give a solution specific to entity framework, but I think putting the articles into a sorted list and letting the list do the work might be the easiest way.
I think the best approach here would be to implement a Swap method that takes two News objects and swaps their OrderId, which I am assuming is numeric.
So the idea would be that you would pass this method the object that was clicked on, as well as either the one above (if the user clicked +) or the one below (if they clicked -). If you do it this way then you avoid the task of trying to find the next or previous item.
In the case of drag and drop, the task is a little different. You would first need to retrieve all the items between (and including) the item being dragged and the drop target, ordered by OrderId. From there you swap the dragged item with the next or previous item (depending on direction), and continue doing so until you have swapped it with the drop target.
Related
This is my first post on stackoverflow, even though i've been lurking in the shadows for past 10 years. :D
So, I have a task to scrape data off of a site which contains 3 cascade select lists / dropdowns, call it what ever you like. As I've played around selenium, I thought of giving a try with it. BUT I keep getting this :
"OpenQA.Selenium.StaleElementReferenceException"
I get the gist of it:
1) I declare a first list "Makes" of IWebElements which load up with all elements from first dropdown. => **works fine**
2) Then I iterate through the list using foreach, something like
foreach (var make in makes)
{
make.click() // step 3
... // step 4
}
3.As seen above I click on the first element so it can fetch data for another dropdown
4.I point to another list "Models" and repeat the process for iterating the second list and console.writeline it's content.
So it gives me first element from the first list "makes", all of members from the second list "Models", as it is supposed to. But as soon as it proceeds to another member of the first list (first foreach), it says that Make is stale "OpenQA.Selenium.StaleElementReferenceException"
Cheers!
So I have a SP list with about 100k items (voucher codes) in it.
Each of them has columns for State (Active/Used), Value (10,20,30) Group (Normal, Special) and Code (random alphanumeric). Each of the columns are indexed
I can't use CAML to get the next active code for a certain group and value, because each of the criteria would return > 5k items (list view threshold).
So what would be the most efficient way to retrieve the next code?
As the list is continuously growing, loading all items with SPListItemCollectionPosition is not really an option. Isn't there a better way?
It should work for onprem, as well as spOnline
Thank you
If your Code is a progressive number, increasing at any new entered item, you have 2 options:
Create a service List that you can name something like CodeCounter, here you store the last created Code in a column. Create a workflow in main list, starting at item creation. This workflow will read the last created Code from service list, then update it to Code+1 and in parallel manages the update (optional) of main code in main list
use an event handler (farm solution, here the query surely works better)
In a dropdown I've got a list of country of this type:
Text: "Italy" Value :"IT"
I need a copy of one of the country in the top of the list referred to the current language of the portal I'm working in, so the user can both select the first or the one into the list. Is just a hint we can say.
So I've just added a copy in this way:
cmbNazione.Items.Insert(0, cmbNazione.Items.FindByText(valori.Rows[0]["M_SOAAuthorityCountry"].ToString().ToUpper()));}
This code works fine. I got my duplicate value and I can select it without problem.
I am stuck when I already have a country that I have to set into the dropDown.
I just wrote that:
cmbNazione.Items.Insert(0, cmbNazione.Items.FindByText(valori.Rows[0]["M_SOAAuthorityCountry"].ToString().ToUpper()));
cmbNazione.ClearSelection();
cmbNazione.Items.FindByText(valori.Rows[0]["M_SOAAuthorityCountry"].ToString().ToUpper()).Selected = true;
The problem is that I receive the error: Cannot have multiple items selected in a DropDownList.
In fact if I check I got both the list Items (first, and the identical in the list) with the prop : selected = true. If I try to make one false both change to false. I cannot use them separately.
I can't understand why I can use them correctly when I select manually, as a user, but not when I try to select them through code.
I also tried something like :
cmbNazione.SelectedIndex = cmbNazione.Items.IndexOf(cmbNazione.Items.FindByText(valori.Rows[0]["M_SOAAuthorityCountry"].ToString().ToUpper()));
But nothing. I'll every time have multiple items in the list of the selected
You should not have a duplicate value as it will confuse the user (if the value is on 2-3 position already) and architecture as retrieval may lead to 2 values being selected.
Your use case seem like you are offering the most commonly used value as the first one and then the remaining. If this is the case, follow the approach outlined below.
Find the ListItem required, then remove it from the list and add on the 1st position. Then mark it as selected.
var preferredItem = cmbNazione.Items.FindByText(...);
if (preferredItem != null) {
cmbNazione.Items.Remove(preferredItem);
cmbNazione.Items.Insert(0, preferredItem);
cmbNazione.SelectedItemIndex = 0;
}
This way, there will be single item being selected and preserve the sanctity of the item (underlying value etc) while still allowing user to have the preferred one on top of list. You can chose to have this as 'pre-selected' or let user select it explictly.
Let's say we have a code list of all the countries including their country codes. The country code is primary key of the Countries table and it is used as a foreign key in many places in the database. In my application the countries are usually displayed as dropdowns on multiple forms.
Some of the countries, that used to exists in the past, don't exist any more, for example Serbia and Montenegro, which had the country code of SCG.
I have two objectives:
don't allow the user to use these old values (so these values should not be visible in dropdowns when inserting data)
the user should still be able to (readonly) open old stuff and in this case the deprecated values should be visible in dropdowns.
I see two options:
Rename deprecated values, for instance from 'CountryName' to '!!!!!CountryName'. This approach is the easiest to implement, but with obvious drawbacks.
Add IsActive column to Countries table and set it to false for all deprecated values and true for all other. On all the forms where the user can insert data, display only values which are active. On the readonly forms we can display all values (including deprecated ones) so the user will be able to display old data. But on some of my forms the user should be able to also edit data, which means that the deprecated values should be hidden from him. That means, that each dropbox should have some initialization logic like this: if the data displayed is readonly, then include deprecated values in dropbox and if the data is for edit also, then exclude them. But this is a lot of work and error prone too.
And other ideas?
I deal with this scenario a lot, and use the 'Active' flag to solve the problem, much as you described. When I populate a drop-down list with values, I only load 'active' data and include upto 1 deprecated value, but only if it is being used. (i.e. if I am looking at a person record, and that person has a deprecated country, then that country would be included in the Drop-downlist along with the active countries. I do this in read-only AND in edit modes, because in my cases, if a person record (for example) has a deprecated country listed, they can continue to use it, but once they change it to a non-deprecated country, and then save it, they can never switch back (your use case may vary).
So the key differences is, even in read-only mode I don't add all the deprecated countries to the DDL, just the deprecated country that applies to the record I am looking at, and even then, it is only if that record was already in use.
Here is an example of the logic I use when loading the drop down list:
protected void LoadSourceDropdownList(bool AddingNewRecord, int ExistingCode)
{
using (Entities db = new Entities())
{
if (AddingNewRecord) // when we are adding a new record, only show 'active' items in the drop-downlist.
ddlSource.DataSource = (from q in db.zLeadSources where (q.Active == true) select q);
else // for existing records, show all active items AND the current value.
ddlSource.DataSource = (from q in db.zLeadSources where ((q.Active == true) || (q.Code == ExistingCode)) select q);
ddlSource.DataValueField = "Code";
ddlSource.DataTextField = "Description";
ddlSource.DataBind();
ddlSource.Items.Insert(0, "--Select--");
ddlSource.Items[0].Value = "0";
}
}
If you are displaying the record as read-only, why bother loading the standing data at all?
Here's what I would do:
the record will contain the country code in any case, I would also propose returning the country description (which admittedly makes things less efficient), but when the user loads "old stuff", the business service recognises that this record will be read only, and you don't bother loading the country list (which would make things more efficient).
in my presentation service I will then generally do a check to see whether the list of countries is null. If not (r/w) load the data into the list box, if so (r/o) populate the list box from the data in the record - a single entry in the list equals read-only.
You can filter with CollectionViewSource or you could just create a Public Enumerable that filters the full list using LINQ.
CollectionViewSource Class
LINQ The FieldDef.DispSearch is the active condition. IEnumerable is a little better performance than List.
public IEnumerable<FieldDefApplied> FieldDefsAppliedSearch
{
get
{
return fieldDefsApplied.Where(df => df.FieldDef.DispSearch).OrderBy(df => df.FieldDef.DispName);
}
}
Why would you still want to display (for instance) customer-addresses with their OLD country-code?
If I understand correctly, you currently still have 'address'-records that still point to 'Serbia and Montenegro'. I think if you solve that problem, your current question would be none-existent.
The term "country" is perhaps a little misleading: not all the "countries" in ISO 3166 are actually independent. Rather, many of them are geographically separate territories that are legally portions or dependencies of other countries.
Also note that 'withdrawn country-codes' are reserved for 5 years, meaning that after 5 years they may be reused. So moving away from using the country-code itself as primary key would make sense to me, especially if for historical reasons you would need to back-track previous country-codes.
So why not make the 'withdrawn' field/table that points to the new country-id's. You can still check (in sql for instance, since you were already using a table) if this field is empty or not to get a true/false check if you need it.
The way I see it: "Country" codes may change, country's may merge and country's may divide.
If country's change or merge, you can update your address-records with a simple query.
If country's divide, you need a way to determine what address is part of what country.
You could use some automated system do do this (and write lengthly books about it).
OR
(when it is a forum like site), you could ask the users that still have a withdrawn country that points to multiple alternatives in their account to update their country-entry at login, where they can only choose from the list of new country's that are specified in the withdrawn field.
Think of this simplified country-table setup:
id cc cn withdrawn
1 DE Germany
2 CS Serbia and Montenegro 6,7
3 RH Southern Rhodesia 5
4 NL The Netherlands
5 ZW Zimbabwe
6 RS Serbia
7 ME Montenegro
In this example, address-records with country-id 3, get updated with a query to country-id 5, no user interaction (or other solution) needed.
But address-records that specify country-id 2 will be asked to select country-id 6 or 7 (of course in the text presented to the user you use the country-name) or are selected to perform your custom automated update routine on.
Also note: 'withdrawn' is a repeating group and as such you could/should make it into a separate table.
Implementing this idea (without downtime) in your scenario:
sql statement to build a new country-table with numerical id's as primary key.
sql statement to update address-records with new field 'country-id' and fill this field with the country-id from the new country-table that corresponds with country-code specified in that record's address-field.
(sql statement to) create the withdrawn table and populate the correct data with in it.
then rewrite your the sql statements that supply your forms with data
add the check and 'ask user to update country'-routine
let new forms go live
wait/see for unintended bugs
delete old country-table and (now unused) country-code column from the "address"-table
I am very curious what other experts think about this idea!!
I was wondering if anyone has a good solution to a problem I've encountered numerous times during the last years.
I have a shopping cart and my customer explicitly requests that it's order is significant. So I need to persist the order to the DB.
The obvious way would be to simply insert some OrderField where I would assign the number 0 to N and sort it that way.
But doing so would make reordering harder and I somehow feel that this solution is kinda fragile and will come back at me some day.
(I use C# 3,5 with NHibernate and SQL Server 2005)
Thank you
Ok here is my solution to make programming this easier for anyone that happens along to this thread. the trick is being able to update all the order indexes above or below an insert / deletion in one update.
Using a numeric (integer) column in your table, supported by the SQL queries
CREATE TABLE myitems (Myitem TEXT, id INTEGER PRIMARY KEY, orderindex NUMERIC);
To delete the item at orderindex 6:
DELETE FROM myitems WHERE orderindex=6;
UPDATE myitems SET orderindex = (orderindex - 1) WHERE orderindex > 6;
To swap two items (4 and 7):
UPDATE myitems SET orderindex = 0 WHERE orderindex = 4;
UPDATE myitems SET orderindex = 4 WHERE orderindex = 7;
UPDATE myitems SET orderindex = 7 WHERE orderindex = 0;
i.e. 0 is not used, so use a it as a dummy to avoid having an ambiguous item.
To insert at 3:
UPDATE myitems SET orderindex = (orderindex + 1) WHERE orderindex > 2;
INSERT INTO myitems (Myitem,orderindex) values ("MytxtitemHere",3)
Best solution is a Doubly Linked list. O(1) for all operations except indexing. Nothing can index SQL quickly though except a where clause on the item you want.
0,10,20 types fail. Sequence column ones fail. Float sequence column fails at group moves.
Doubly Linked list is same operations for addition, removal, group deletion, group addition, group move. Single linked list works ok too. Double linked is better with SQL in my opinion though. Single linked list requires you to have the entire list.
FWIW, I think the way you suggest (i.e. committing the order to the database) is not a bad solution to your problem. I also think it's probably the safest/most reliable way.
How about using a linked list implementation? Having one column the will hold the value (order number) of the next item. I think it's by far the easiest to use when doing insertion of orders in between. No need to renumber.
Unfortunately there is no magic bullet for this. You cannot guarentee the order of any SELECT statement WITHOUT an order by clause. You need to add the column and program around it.
I don't know that I'd recommend adding gaps in the order sequence, depending on the size of your lists and the hits on the site, you might gain very little for the over head of handling the logic (you'd still need to cater for the occasion where all the gaps have been used up). I'd take a close look to see what benifits this would give you in your situation.
Sorry I can't offer anything better, Hope this helped.
I wouldn't recommend the A, AA, B, BA, BB approach at all. There's a lot of extra processing involved to determine hierarchy and inserting entries in between is not fun at all.
Just add an OrderField, integer. Don't use gaps, because then you have to either work with a non-standard 'step' on your next middle insert, or you will have to resynchronize your list first, then add a new entry.
Having 0...N is easy to reorder, and if you can use Array methods or List methods outside of SQL to re-order the collection as a whole, then update each entry, or you can figure out where you are inserting into, and +1 or -1 each entry after or before it accordingly.
Once you have a little library written for it, it'll be a piece of cake.
I would just insert an order field. Its the simplest way. If the customer can reorder the fields or you need to insert in the middle then just rewrite the order fields for all items in that batch.
If down the line you find this limiting due to poor performance on inserts and updates then it is possible to use a varchar field rather than an integer. This allows for quite a high level of precision when inserting. eg to insert between items 'A' and 'B' you can insert an item ordered as 'AA'. This is almost certainly overkill for a shopping cart though.
On a level of abstraction above the cart Items let's say CartOrder (that has 1-n with CartItem) you can maintain a field called itemOrder which could be just a comma - separated list of id(PK) of cartItem records relevant . It will be at application layer that you require to parse that and arrange your item models accordingly . The big plus for this approach will be in case of order reshufflings , there might not be changes on individual objects but since order is persisted as an index field inside the order item table rows you will have to issue an update command for each one of the rows updating their index field.
Please let me know your criticisms on this approach, i am curious to know in which ways this might fail.
I solved it pragmatically like this:
The order is defined in the UI.
The backend gets a POST request that contains the IDs and the corresponding Position of every item in the list.
I start a transaction and update the position for every ID.
Done.
So ordering is expensive but reading the ordered list is super cheap.
I would recommend keeping gaps in the order number, so instead of 1,2,3 etc, use 10,20,30... If you need to just insert one more item, you could put it at 15, rather than reordering everything at that point.
Well, I would say the short answer is:
Create a primary key of autoidentity in the cartcontents table, then insert rows in the correct top-down order. Then by selecting from the table with order by the primary key autoidentity column would give you the same list. By doing this you have to delete all items and reinsert then in case of alterations to the cart contents. (But that is still quite a clean way of doing it) If that's not feasible, then go with the order column like suggested by others.
When I use Hibernate, and need to save the order of a #OneToMany, I use a Map and not a List.
#OneToMany(fetch = FetchType.EAGER, mappedBy = "rule", cascade = CascadeType.ALL)
#MapKey(name = "position")
#OrderBy("position")
private Map<Integer, RuleAction> actions = LazyMap.decorate(new LinkedHashMap<>(), FactoryUtils.instantiateFactory(RuleAction.class, new Class[] { Rule.class }, new Object[] { this }));
In this Java example, position is an Integer property of RuleAction so the order is persisted that way. I guess in C# this would look rather similar.