I've got a gridview with a list of categories. In the database (MSSQL2008), the category table has a SortOrder(INT) NULL field.
Currently categories are retrieved using:
Galleries.DataSource = From G In DB.GalleryCategories Order By G.SortOrder, G.Name
Now, what I need to be able to do is add "Move Up" and "Move Down" buttons to each row to allow the user to sort the items in an arbitrary way.
My initial thoughts are along the lines of:
Identify ID of selected item.
Identify ID of item before/after selected item.
Swap of identified items in the DB SortOrders.
I would then have make the sortorder NOT NULL and make sure it's initialised to a unique number
I'd appreciate any alternative suggestions / comments on this approach
Many thanks
I have generally seen it done this way, and have done it myself
SortOrder is an int
Each item increases by 10 (so, 10,20,30,40) or suitable increment
To move an item up, subtract 15
To move an item down, add 15
To insert an item, take the target and add/subtract 1
Apply a NormalizeSort() routine which resets the values to even intervals
10,20,25,30,40 => 10,20,30,40,50
That makes it all pretty simple, since inserting something above something else is just:
list.Add( New Item(..., target.SortOrder +1) )
list.NormalizeSort()
// or
item.SortOrder += 11, etc
If you want to make it a decimal, then you can just make it all sequential and just add .1, etc to the sort order and re-normalize again.
// Andrew
I believe
Galleries.AllowSorting = true;
would be far enough ;)
Related
I'm trying to implement multiple record selection feature on a grid.
It is very similar to http://www.tek-tips.com/faqs.cfm?fid=3831
It adds an extra column with check boxes. I want those check boxes!!
But it depends on a extra logical field in the underlying table. It need to create a class clscheck which inherits CHECKBOX. I'm not sure why this CLICK procedure is needed for the checkbox.
PROCEDURE CLICK
IF DODEFAULT()
KEYBOARD '{DNARROW}'
ENDIF
ENDPROC
When I removed it, row selection did not work correctly as expected. Why this?
Here is my requirement:
1) I don't want to add an extra logical field in the underlying table.
2) To work with controls in the grid, I think AllowCellSelection must be .T. I want AllowCellSelection = .F. because I don't need to work with any control in the grid except the check boxes. I need to work only with check boxes. The other columns will be read-only.
3) Can I have selected list without the logical field in the underlying table?
4) Can I remove the usage of KEYBOARD '{DNARROW}'?
In fact, I have a grid which is AllowCellSelection = .F., but it only provides single selection.
I need to enhance it with multiple selection, thus, I just want to add an extra column with check boxes so that user can know he can select multiple records.
No need Shift+Click or Ctrl+Click which is not familiar with idiot users.
I have found this - http://www.tek-tips.com/faqs.cfm?fid=433
It also depends on an extra logical field and it depends Shift+Click and Ctrl+Click.
What you are seeing is quite common for multi-select grids. I've used them SIMILAR to this in the past. However, you are afraid of the extra column in the underlying table. That may/not be true. You don't always have to update the ORIGINAL table, but a temporary CURSOR you are presenting to the user. Ex: If you want to display a list of employees in a table. No, you don't want to keep adding this column to the original employee table as then anyone else trying to do multi-select could falsely get your selection. However, if you pulled into your own local cursor and presented to the user, then no problem. Example...
Thisform.YourGrid.RecordSource = "Employees"
(bound directly to your employee table -- not necessarily the right thing)
vs
use in select( "C_MultiPickEmployees" )
select ;
.F. as IsChosen, ;
E.* ;
from ;
Employees E;
into ;
cursor C_MultiPickEmployees READWRITE
Thisform.YourGrid.RecordSource = "C_MultiPickEmployees"
NOW, you have your extra column without dealing with issues to the underlying table. If you wanted to further filter what you were showing -- such as employees for a certain division/department, then just add that to a WHERE clause, add an Order By if so needed and you are good to go.
As for the "Allow Cell Selection", I've never had to deal with that. I just add a "checkbox" to the first column and set
Thisform.YourGrid.Column[1].CurrentControl = "CheckBoxControl"
(based on the name it is added to the column).
Then, set the column 1's "ControlSource" = "C_MultiPickEmployees.IsChosen" and you should mostly be done.
As for the "CLICK" event trying to force the down arrow. This is more for automatically scrolling to the next record so you can just click, click, click for multiple entries.
Hope this helps clarify things for you.
I have a list of values in a SQL Table which are used to popluate a DropDownList, having a unique Integer as the value of each item and a String as the visible text (via SqlDataSource). There is also a third field in the database which is a flag to indicate whether the list item is active or not (inactive items are not shown in the DropDownList)
Selections made in the dropdown are stored in the database as their integer value (as part of a dataset making up the overall record), not the text value.
Over time, the items in the DropDownList may be removed by marking the items as inactive. However, there is still a need to open old records which may have had a now-inactive item as part of it's data...
My question is, what's the best way to ensure that the missing value included in the dropdown for the old record?
The two methods that spring to mind are to either:
Populate DropDownList with only the currently active items and, when loading a record, catch when the app tries to select a value that doesn't exist, go back to the db to see what it should be (the text value) and manually add it into the dropdown.
or...
Populate DropDownList with all list items (both active and inactive), load the record and then programatically remove all the inactive items (execpt for any that are now selected).
Neither of these seem particularly efficient, so I was wondering whether there is a best practice for this kind of thing?
there are so many optimum ways to do that sort of things, i am defining here a couple of them, use any of following if your Drop down list items count is less than 200 , lets say drop down list is of Products
1)
i) Load all Products records in drop down list and hide the inactive ones by setting visible=false
i) When you load a user record than look for its drop down list value if its visible than select it and enjoy, if its not visible than make it visible by setting its property visible=true and select it and also set its index or id in a flag to change its visibility(visible=false) again after your/users required operation performed.
2)
i) load only active Product records in drop down list ii) while loading a user record also load its product details(name, id, inactive_status) using Joins in sql.
iii) check in that user record if item is inactive then add its record in drop down list as you have all its details now with user details record else just select it.
IMPORTANT NOTE: if you drop down list has items in millions than use ADVANCE SEARCH techniques
The first thing I would do is question your business logic - should you be able to make an item inactive if it is being used as a foreign key in an active row elsewhere? If you make it inactive should it not remove all foreign keys as well?
To answer your question though I would go with a variation on the second idea but filtering in the page like that is probably slower than doing directly with SQL so I guess you have something like this at the moment to populate the dropdown
SELECT * FROM Table WHERE Active = 1
You should already have your record and the foreign key value so I would change it to this
SELECT * FROM Table WHERE Active = 1 OR PrimaryKey = [YourForeignKey]
Then you will always have the selected item but should also be fairly efficient.
my application needs to allow users to insert rows below the current datagrid row. My solution is to to add a row to the dataproviders collection. This works, but the row does not appear beneath the current row the user clicked on.
The Datagrid has a default sort order (date ASC), which re-orders the data...so this seems to affect the position of the row in the grid.
Any ideas how to fix this?
Two possible answers:
1. define your own sort function that sorts according to item order in dataprovider (i.e. it does nothing), and assign it to the sortFunction property
2. simply comment out the sorting of the data inside the component.
I've got a list of items. Users can occasionally select them. Now I want to order the items by their popularity. What's a good weighting function for that?
Constraints:
The weight should be in [0,1)
Recursive calculation is prefered (not required)
Newer events must have more influence than old ones.
I'd favor approved functions. As I've developped something like this once and it worked not as expected.
Now I want to order the items by their popularity.
So you order by the number of times some user selected the item.
The weight should be in [0,1).
Fine, divide by the total number of times some user selected some item plus one.
Recursive calculation is prefered
Why? Maybe I'm missing the point of what you're trying to do because otherwise this constraint is lost on me.
Edit:
Responding to your edit, try
sum ( 1 / age of vote ) / age of item
the sum being taken over all votes for a given item.
If you have a counter of votes per item, you can use a 'fading constant' in order to make older votes "fade away" with time. Something like:
Nvotes(i) = IsClicked(i) + Nvotes(i) * Kfade
where: 0 < Kfade < 1
Thus, whenever a new click is intercepted, all counters are advanced where only the selected item is incremented by 1.
EDIT: Since the total is less than 1, you may want to normalize Nvotes by the total number of clicks so far.
Keep a list items of the items that need sorting. Let each item have a score. Keep a list clicks of the N most recent clicks, in order of decreasing recency. Each item can appear more than once in the list. Choose a constant fade a little smaller than 1. Then do:
for item in items:
item.score = 0.0
bonus = 1.0
for item in clicks:
item.score += bonus
bonus *= fade
Now sort the items by score, highest first.
The score isn't in the range 0 to 1, but i don't see why you actually need that. It would be straightforward to normalise the scores afterwards.
This isn't recursive, but it's straightforward to put in recursive form.
This isn't a known algorithm. I don't know of any known algorithms for this except move-to-front, which is almost certainly more aggressive than you want.
In a specific table I have a SortOrder integer field that tells my page in which order to display the data. There are sets of data in the this field (based on a CategoryID field), and each set will have its own ordering. Users can add/remove/update records in this table.
My question is what is the best way to manage this SortOrder field? I would like to "reseed" it everytime a record is deleted or updated. Is this something I should be using a trigger for? Or should my code handle it and manage the reseeding?
What I used to do is use only odd numbers in the SortOrder field so upon changing the order, I would add or subtract 3 from the current value of the modified item and then do a reseed (order the items again using odd number indexes). Also I used to reseed after every insert or delete.
All you really have to worry about is swapping any two fields. All new entries go to the end and i'm sure you've got a mechanism by which the user can change the order. The order change, move up or down, really is a swap with a neighboring field. All you really care about is that all the fields are sorted properly. Don't let a mathematical sense of aesthetic drive you into creating something overly complex. (You'll end up with holes in your sequence after deletes are made but that's OK. It's an internal sequence marker used for ORDER BY. the numbers don't need to be made contiguous.)