I would like to fetch a number of records from a database to fill a DropDownList that is filled in a OnItemDataBound of a DataList.
I think it might be a bit much to fetch all the records every time a DropDownList is bound since they are the same.
How can this be done?
If I understand your question correctly, you could put your drop down list into a user control, and then output cache it, which would mean the resulting drop down list would not keep making new requests to the database each time it is loaded.
MSDN has quite a good article on output caching:
http://msdn.microsoft.com/en-us/library/hdxfb6cy.aspx
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In My Database I Have 10000000 Records. In GridView First I Am Showing First 10 Records. In Order To See the Next Records User Need to Click Page Numbers ( 1,2,3,------10000). But As I'm Retrieving 10 Records for The First Time GridView Paging is not Showing.
Is There Any Way To Show Paging In ASP.NET GridView Statically ?
For so many records, I won't recommend Paging. You can show Top 20 recently added records and provide options to filter out records. A user can enter keywords. ReQuery and ReBind the GridView with this new result set.
You might also consider using PetaPoco, a Micro-ORM, which will help you fetch paged result.
With so many records, you really need to take into account the exact queries being run to pull back the data.
There are numerous ways of doing data paging ( http://beyondrelational.com/modules/2/blogs/28/posts/10434/sql-server-server-side-paging-with-rownumber-function.aspx ). However, the "best" way is dependent on the exact version of SQL Server you are running.
Essentially, the solutions boil down to you passing a page number and number of records per page through some type of query. Usually a stored procedure as the query can be quite messy.
Once there, you have an option. Either send the total record count back as an OUT parameter in your query and the result set back normally, or you send the total record count back as a column. There are definitely efficiency concerns with both options as one way requires the query to be run twice and the other requires an extra column of data which increases network traffic.
Once you have that solved then you can figure out exactly how you want the UI to work.
I'm populating a GridView with code, setting datasource to the dataset returned by a query. So apparently sorting and paging don't just work magically like if I use a datasourceid= some sqldatasource.
I've found a number of examples of how to do this on the web, but they all appear to re-execute the query every time. Shouldn't the contents of the query be saved in the view state? Is there some way to just get the previous query results and re-sort without having to go back to the database? (Is it saving all the data in the view state? If so, why can't I get to it? It seems pretty dumb to send it all to the user's browser and send it all back, wasting all the bandwidth, if there's no way to get to it.)
Also, if I try to allow paging, it appears I again have to re-execute the query every time the user goes to another page. And if the user sorts and then pages, then I have to remember what the sort order was in a hidden field or some such, so I can re-read the data, re-sort, and then go to the right page.
Given that when you use a data source control all this behavior is built in, I think I'm missing something here. But given all the examples out there that do it this slow, hard way, if I'm missing something, a lot of other programmers are missing it, too.
If you're using an ASP.NET GridView control every time you sort a column or page through the data set then you're making a server postback. Sorting and paging with this particular control has never worked 'magically' and has long been a bugbear of mine.
You can speed things up by storing the data source that you're building the grid from in memory, either as a session or through the ViewState. Both have pros and cons and I suggest you read up.
If at all possible I suggest forgetting the ASP.NET GridView and looking at a client side solution such as the jQuery jqGrid. It uses AJAX calls to sort and page and is much, much faster and less of a headache. The only drawback is the learning curve but believe me it's worth it in the long run.
Yes the gridview re-execute the query every time.
If the query takes too long, you can manually store data in the session, or ViewState. And in the Algorithm that populates the grid just read them directly for it, instead of running the query.
you can, in the page load event, run the query one time when there is no postback (you can check for postback with
if (!Page.IsPostBack){
//Run the query and save it to the session
}
and the the method that populate the grid, should read from the session directly. no need to run the query again
I'm working on a web application, on one page I am inserting records in the database and I want to display the data in a GridView but on a diffrent page. How can I do this?
I know how to display records in a GridView, but I want to know if there are two web pages,
on one page provides the facility to insert the records and U want to display the records in the GridView bit on the second page.
While it is possible to retain the data being inserted without retrieving it from the database, I think it is better to save the data on the first page and retrieve it from the database on the second page.
You can do this by writing inline SQL or a stored procedure. One simple approach would be to pass the resultset into a DataTable and bind a GridView to that.
That does involve more work -- more code and more trips to the database. However, I think it is very useful when performing INSERTs that the web page is updated to display what actually got into the database. Sometimes, this is different from what the user thinks they entered, and they can see the problem immediately.
One question would be how to identify the data that has just been inserted. I can think of several ways to do that. One is to query for all records entered today by the person logged in (which is recorded in the CreatedBy and CreatedDate columns of the database tables). Sort the resultset in descending order of CreatedDate, so that the most recent entries appear at the top of the GridView. Another would be by assigning a batch number to the data entry and retrieving only the data in that batch.
If you really want to hang on to the data entry, you could put it into Session on the first page, and then retrieve it from Session for display on the second page.
Following along the lines of what DOK said, it's also a lot easier to validate data entered by your users in your business logic before you submit it to the database.
Secondly, users can change their minds about data on a webpage frequently. The data on the web could be in an partially-finished state or could have typos or errors in it. If someone else saw this data and believed that it needed to be completed, then you could end up with duplicated entries in the database that would then require reconciliation.
Honestly, your best bet is to use the Session object to hold temporary user data. The MSDN entry for the GridView RowEditing event contains some great source code for this approach. Whenever I have to use GridViews to handle data from the database, I mimic this.
In addition to handling problems with temporary data storage, you can compare the Session object to your database results to determine whether or not new rows have been inserted. This is somewhat costly as it involves overloading the Equals method (and GetHashCode as well, if you follow what Microsoft recommends) and using Equals to iterate over the two collections, comparing the properties of both objects, and determining which records are new based on records that don't exist in your Session object, but do exist in your database object.
It's also worth noting that this approach assumes that you don't delete data from your database, but set the status of a record in your database to "Deleted" -- if that's a boolean field or an sequence of codes you use to describe the state of rows in a table.
I used bind all GridViews, DetailViews etc. on my page using an ObjectDataSource (unless it wasn't possible to do so). Recently, I've started binding all my contols programatically. I find this a lot cleaner and easier, though some may disagree.
Binding with a ObjectDataSource obviously has it advantages and disadvantages, as does doing it programatically.
Say I bind a GridView programatically (e.g. GridView1.DataSource = SomeList), when I change page on the GridView, I have to also code this. Each time the page changes I have to call GridView1.DataSource = SomeList again. Obviously with a ObjectDataSource I don't need to do this. I normally stick my SomeList object into the ViewState so when I change page I don't need to hit the database each and every time.
My question is: Is this how the ObjectDataSource works? Does it store it's data in the ViewState and not hit the database again unless you call the .Select method? I like to try and get the best performance out of my applications and hit the database as few times as possible but I don't really like the idea of storing a huge list in the ViewState. Is there a better way of doing this? Is caching per user a good idea (or possible)? Shall I just hit the database everytime instead of storing my huge list in the ViewState? Is it sometimes better to hit the database than to use ViewState?
Does it store it's data in the ViewState and not hit the database again unless you call the .Select method?
No its not save the data in ViewState. In the view state gridview and other similar lists, saves the General Status, eg the sort column, the page, the total pages, the control state, but not the Data.
Is caching per user a good idea
The caching per user on server side is not so good idea except if the caching is last for few minutes only or/and the data that you going to cache is very small. If you cache per user large amount of data for long time they going to grow too much especial if a user starts to read a lot of pages, that at the end you have the same problem.
Now you have to show a large amount of data that come from the relation of many tables, then maybe is better to cache the full relation of the tables to "one flat table".
Shall I just hit the database everytime instead of storing my huge list in the ViewState?
This is also depend from how fast you have design the reading of your data. For me is better to keep the ViewState small, and keep there only informations that you need to make the actions on your page, and not data.
I'm writing an internal web application that is used to look up credit checks. I'm using ASP.NET for this website.
I have a SQL Query that I have to query the credit check database and it returns a datatable of results. After the person clicks search, I run the query and bind the returned datatable to the Gridview every time the user clicks the search button.
This works fine, and it populates my gridview like it should.
How do I maintain the data that is bound to my gridview beyond postback? For example, lets say a person clicks Page 2 of the paginated gridview... how do I keep from losing the data of the gridview during that postback?
Currently I am storing the datatable in session[] but I don't think I should be doing this, because the size of this table is very large (sometimes hundreds of thousands of results!)
Do I need to re-query the database for each postback? The query takes a decent bit and I'd rather not if I could help it.
What is the common solution here?
If you are storing the data in the session I would make sure viewstate is turned off and you are rebinding it on each postback so at least your not storing all that data in 2 places.
You could also considered leaving the viewstate on and changing logic that grabs the session data to bring back one page of data at a time? You would take in the current page and JUST return that page's data so that you could get all the data at first and store it in the session. Then if any other postback actions occurred during that page view where nothing was really going on with the grid you wouldn't have to rebind each time.
I have found that most of the issues I have run across in the past due to too much data being displayed in a grid were more design issues and I would step back and look at the overall problem that was trying to be solved and implement another solution to not have to display so much data. Usually a customer/user asks for everything because they don't consider any alternatives or the impact of their request.
Several things:
Clicking on "Page 2" should not result in a postback - it should be a simple GET request.
Do not allow GridView to store its data in the ViewState: cache data manually and "rebind" datasource on each request
Use ASP.NET MVC