I have a form that contains several comboxes that their data is coming from the server.
I need to load all of the combobox's data before the form data is loading (from the server).
If Extjs had allow synchronized requests, I would make every combo as synchronized, and after that loading the form data.
but as far as i know, everything needs to be done via callbacks, which makes the form a bit "re-use-less"
Any idea how to salve it?
Just to make it clear, I am talking about a situation of editing an employee details for example, which its form data contains:
first_name, last_name, city_id(bombo),country_id(combo)
And loading the combobox data of city_id and country_id is critical for the selectedValue issue.
Thanks
combo_store.load();
combo_store.on('load', function(st, records, options)
{
// callback called after data loading in combo
// you can load other data
});
Related
I have several ASP.NET pages that store an object in the session and use it for data binding etc. The object in the session is referenced in several pages of a 'wizard'.
I want users to be able to have several tabs open and work on several different objects stored in the session at the same time.
I am using a URL param to do this, where the param is incremented each time the page is hit, i.e:
http://server/MyPage.aspx?action=1
http://server/MyPage.aspx?action=2
And my session access is simply
return (MyObject) Session["MyObject" + Request.Params["action_id"]]
This is fine, but it doens't work for object data sources when they are data bound - the error is "Request is not available in this context"
How can I get an ID that I can retrieve on the server side reliably in callbacks and page loads? The ViewState doesn't seem to be available in
Ah, the trick is to use
System.Web.HttpContext.Current.Request
I am totally new to classes and OOP, so please bear with me.
I am creating a large scale web app which I'm trying to keep tidy by creating my own classes.
For instance I have a Public Class Product which has several properties. One way I am using it is on page load a product ID is assigned to the ID property which in turn gets the details for that product and assigns the various data to the other properties. So within my code I can used for example product.price or product.description and get the appropriate values. This has worked fine, but I found that because the class was initiated on page load it was getting the data from the DB each time that the page refreshed. I stopped this by using an If Not IsPostback to initiate the class. This meant that the data was pulled in only on the initial page load. So far so good.
I then needed to compare a value in a textbox with a property of the product. I have a textchanged event with
If textbox1.Text <> product.description Then....
but here I get a wavy line under product.description and VS2010 is saying that the object is not defined. Its Dim'd in the page.load so I moved the Dim statement outside the page class so that it will be accessible to all events on the page.
The dim statement is Dim product as New product
In my not ispostback chunk of code I have for example product.ID = 1 which will get all the product properties for product 1
The wavy line has gone but when I run the page all works fine on page load. Data is displayed so my product class is working fine. As soon as I make a change in textbox1 and the event triggers product.description is nothing. It got reinitalised.
How do I stop this from happening...
Your "Product" is not persisted between postbacks.
Only control objects in aspx page are persisted/restored automatically.
To remedy this there are multiple approaches.
If Product is loaded via setting "Product.id=1" then what I woudl do is have a hiddenfield that receives the value of the product.id during prerender event (to save it in the page) and in an init event I would restore the "Product.id=hiddenfield.value" but only when it is a postback to reload your object.
EDIT
Thanks for picking my answer. I'll elaborate a little on the various ways to deal with this and why I suggested my answer.
Store Key in HiddenField Reload from DB:
PROS: Product is always Fresh/Correct/Current values. Corresponding to the database. Databases are very efficient to return a record based on a primary key. Very little data is sent to and posted back from the client browser. Low complexity. Each page opened by the client is safely isolated.
CONS: Multiple database transactions. If the DB is already strained or extremely massive you may need to consider even the smallest efficiency gain, but this is not common or likely on a primary key based record
Session State (store entire object):
PROS: Lowest time to "load" object since it's available in memory already once loaded. Less DB Transactions. No data piggy backed to the client and back again.
CONS: Object can become "out-of-date" if altered in the DB. Users who open multiple pages of your application can end up getting the wrong object if both require a different "Product", so instead to be totally safe you need a more complex structure in place to store more then one product or store them based on some kind of key (such as the product ID). Server Memory is used, if serving thousands of users or your product data is large it can become an issue, especially if you do this in many pages with many objects.
Serialization (store the entire object in the page in a field, similar to event state):
PROS: Once loaded, the Database is accessed only once for a specific product, then the product is held, in it's entirety inside the page, it is recreated by the server from the data in the field or via viewstate. Each page opened by the client is safely isolated. Is fairly easy to implement storing in ViewState of the Page.
CONS: Object can become "out-of-date" if altered in the DB. ALLOT more data is added to your page responce and the users next page request. Is more complex to implement because the object needs to be designed to be serialized correctly. Complex objects require allot of manual code to be serialized successfully.
again, there are many other ways to deal with this, such as storing items in a synclocked dictionary style object global to the application, but is considerablby more and more complex as you go.
This is likely the standard ASP.NET page life cycle problem.
After you initialize the page, it gets sent to the user's browser. When the user clicks on something, the browser sends a postback request back to your application. The view state allows the textbox1 object to remember what was in its Text property. However, your Page_Load ran from scratch, and, yes, everything including your product object got recreated from scratch.
If you want your product object to "remember" what it knew before the postback, you'll have to remind it. One way would be to store the initialized value in Session state, and then refresh your product object during the postback section of the Page_Load method.
Every time you do a postback, you're working with a new instance of your page class. The prior copy of your class was thrown away and probably disposed before your browser even rendered the page to the screen.
If you want to persist a value across http requests (of which postbacks are just one type), then you need to put it somewhere like the Session.
we have an architectual problem with our data grid. The grid supports searching, paging and sorting using a linq2entity query, that contains all of the above parameters.
At some pages, the grid should not display the content from the database (e.g. column 'name'), but the translated ressource, loaded by the Resource Provider.
Our Resource Provider gets the translations from the database and caches them to the application cache to avoid unneccessary trips to the database.
At this point, we have the following possibilities:
No searching, sorting and paging on the databse, so loading all rows, then load the translations from the Resource Provider, then do the searching, sorting and paging at the application.
Bad performance, because the database is very big
Searching, sorting and paging on the database, then load the ressources for the results.The Displayed Values will not match to the search and sort configuration
Get the Resources directly from the database, within the linq query.
The Ressource Provider Caching cannot be used. The Join with the Resource Provider Texts will be very bad and slow
Every possibility is very bad, but I can't think of another solution. Any good suggestions? How are these problems solved in other software?
You can do it by bring the associated filtered records from the database and keep it in ViewState.
How can you improve the Performance?
You can make use of JSON / Page Methods for Database Callings. I will explain it to you with the help
of an example.
Click here to check the code for GridView Bindings using JSON
Mark Up With JSON
I am calling the Code Behind methof from Client side
Code Behind
Output
Click here to check the output in case of Update Panels
Is application is holding too much memory then you need a Doctor like Red Gate Ants Memory Profiler. Click here to see more details about it
Make sure to use the Using Statements to avoid Memory Out of Exceptions
using (SqlConnection connection = new SqlConnection())
{
connection.Open();
//Also for SqlCommand... Sample code...
using (SqlCommand cmd = new SqlCommand())
{
}
using (SqlTransaction transaction = connection.BeginTransaction())
{
transaction.Commit();
}
}
Are you aware about the Teleric Grid? It loads all the records first from the database and keeps in Cache. In order to go for this you must use Paging and Disposing the objects is mandatory. Teleric Grid shows these records in Paging. Thus you can avoid the rendering issue to get rid of displaying all records in once.
i don't understand your question properly but if you want to all operations on translated resource you have to store translated resource in database then get them in to session object and apply filter on it if it is either in form of table or list then give source to grid which has to configured as work with translated resource which is filtered from session object.
Hello friends I have a list box control in my asp.net project.
I want to know how to get selected index to set currently updated item in database.
Please help me with this. Do i need to perform some data base operation to find the key for currently updated data and then i'll have to set it or there exist some property to deal with this? thanks in adavance
One thing to watch out for, which I have come accross more than once is that if you call your CompanyListBox() method in your Page_Load method, you will lose the selected index unless it is only called on the first page load. To make sure of this, place your call to CompanyListBox() within the following block:
if(!Page.IsPostBack)
{
CompanyListBox();
}
You can access the selected index in your postback by using the following code:
var id = (Int32)listCompany.SelectedItem.Value
Then it is up to you to use that in your data access to update the record in the database. Looks to me that you are using some kind of framework or manager class for your database access. The companyManager should have methods for saving your updated item to the database. Good luck.
I am a VB.net winforms programmer attempting to build an ASP.Net app. I use data classes(objects) through reflection in most of my vb projects and was trying to adapt it to ASP.net using the VB code behind. I have a webpage that serves as an add/edit page for contact info. I instatiate my class which grabs the contact data from the data base then I have a process that loops through the controls on the form and matches up with a property in the data class. I can display data no problem. When I edit data and click the submit button my code calls a then loops through the controls on the form again and matches the control to the property of the data class to update the property of the class. However, my data class is no longer valid. I know web programming is different then winforms but I can't seem to get over the hump on this one. Is this the wrong way to go about this? Is my data class only available on the server side? Do I just reinstantiate the initial class and then loop through the propeties and change what the user changed and then call the update method (see redundant)? How can I get data class into a session object (I made an attempt in the past but was under tight deadlines and had to abandon it, maybe I need to revisit it?)?
Thanks
If you decide to keep some of your data in Session, you owe it to yourself to look at this post. Your code will be much cleaner and easier to maintain.
Yes, you need to reload the data class from the database as one option, or use an alternative approach. The reason is web is stateless, so all local variables are destroyed then the server side page unload process occurs. This means that in between requests, you need something to store your data.
You can read/write an object via the Session colleciton, as so:
Session["A"] = myobj;
myobj = (ObjType)Session["A"];
And so session stores an object for a specific user. Alternatively, cache stores application level data, so one instance of an object is available to all users (where session is unique to each user). You can make cache unique to a user by appending a user ID to the cache string.
var o = Cache.Get("A");
if (o != null) { .. }
Cache.Add("A", o, ...);
And so these mechanisms help you temporarily retain data.
You need to save your data class somewhere, usually in a session variable, otherwise it goes away as soon as the page gets sent back the user. Or else you need to recreate the data class again upon posting.