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.
Related
I have a list of Task objects.
I have a template which contains a modal form to edit a task.
When a user clicks the link to a single Task I want to set the task to be edited to the Task that was clicked and then render the form.
I'm trying it with reactive variables and Tracker.depend. But I haven't quite gotten it working yet. The data on Template.taskUpdateForm doesn't get set properly.
Please see this commit to see what I'm working on.
https://github.com/laran/eisenhower/commit/e89890d49f5b772849d09fd1f719a6cdafa58125
When you click on a task to edit, just store it's _id or the whole task in a Session variable, and in the helper function for your modal use that same session variable. No need to worry about Tracker depend. This always works for me.
I was setting the selectedTask to the wrong thing. I just needed SelectedTask.set(this.task) instead of SelectedTask.set(this)
I have written SQL Server class and which contains all methods for insert, update, delete, execute stored procedure.
Now I have created a object of this class on Default page load and using class methods
to implement database operations.
Now if i am on second page and want to do database operation. I need to again create the database object.
Is there any way that can i only create it initially and use on other pages ?
You can look into Singleton pattern.
Click here for the MSDN article on it
ASP .NET solves many of these issues with the help of User Controls.
by using user control you can do code re usability
so you should go for user control
bellow link help you to create user control
http://www.codeproject.com/Articles/1739/User-controls-in-ASP-NET
I need to pass a Infragistics ultrawebtree from a page to another. I used Session("data") for this and then I just access it from another page. But when I assign the session value after casting to a Infragistics ultrawebtree control in my second page, it doesnot build the tree structure and it is invisibile. Is I am wroung in this approach, is there any other way to pass the entire tree structure from one page and display it into another page. Any help is appreciated
If anything, I would store the datasource in session instead of the tree. Storing the entire control in session creates a lot of unnecessary overhead, and limits your options per implementation on the next page.
EDIT: You should be able to export the tree structure to XML format, and store the XML in session. According to the documentation there should be WriteXmlDoc() and WriteXmlString() functions available. There's also ReadXmlDoc() and ReadXmlString() functions you can use to repopulate the tree on the next page.
Here's the documentation for the UltraWebTree. You'll see these methods under the Public Methods section:
Only the data should be stored in session. Storing controls in session is likely to cause issues because the control will be disposed during page unload and controls shouldn't be accessed after being disposed which is what would happen when accessing the control from session. See Why Controls Shouldn't be Stored in Session for more details.
alt text http://img3.imageshack.us/img3/1488/advancedsearch.png
I'm building an "Advanced Search" interface in an ASP.NET application. I don't need SO to write this thing for me, but I'm stuck on a specific problem regarding dynamic controls and ViewState. I would like some direction for how to approach this. Here's my situation:
Ingredients:
A serviceable set of API objects representing entities, fields, and searches, which handles constructing a search, generating SQL, and returning the results. So that's all taken care of.
ASP.NET 3.5
Desired Interface Functionality:
(1) On initial page load, the interface gets a preconfigured Search object with a set of SearchCriterion objects. It binds them into a set of controls (see image above.)
Some search items are simpler, like:
Field (DropDownList) | Operator (DropDownList) | Value (TextBox)
Search Criterion controls for some field types have important information stored in viewstate, like:
Field (DropDownList) | Operator (DropDownList) | Value (DropDownList) where the "Value" dropdownlist is populated by a database query.
Some fields are lookups to other Entities, which causes a chain of field selectors, like:
Field (DropDownList) Field (DropDownList) | Operator (DropDownList) | Value
(2) The user modifies the search by:
Adding and Removing search criteria by clicking respective buttons
Configuring existing criteria by changing the Field, Operator, or Value. Changes to Field or Operator will require the control to reconfigure itself by changing the available operators, changing the "Value" input control to a different type, or adding/removing DropDownLists from the "Fields" section if Lookup-type fields are selected/unselected.
(3) Finally, the user hits "Search" to see their results.
The Problem:
As you probably already know if you're answering this question, controls added dynamically to the page disappear on postback. I've created a UserControl that manipulates the control collection and neatly accomplishes step (1) above as you can see in the attached image. (I'm not concerned about style at this point, obviously.)
However on Postback, the controls are all gone, and my Search API object is gone. If I could get the dynamically generated control collection to just play nice and stick in ViewState, I could examine the controls on postback, rebuild the Search object, then handle control events neatly.
Possible Solutions
I could make the Search object serializable and store it in viewstate. Then on page load I could grab it and reconstruct the control collection at page load time. However I'm not sure if this would play nicely with controls raising events, and what happens to the viewstate of Drop-down lists that contain data from the database - could I get it back? It's highly undesirable for me to have to re-query the database on every postback.
I could develop a custom server control (see this link) for this kind of thing... but that is a new topic for me and would involve some learning, plus I'm not totally sure if a custom server control would work any more nicely with non-fixed control collections. Anybody know about that?
I was thinking that I might be able to accomplish this using databound controls - for example I could bind my criterion collection to a repeater which has a fixed control collection (maybe hide the non-used "value" controls, use an inner repeater for the "Field" drop-down lists). Then all the information would stay in ViewState... right?
Any new ideas would be greatly appreciated.
thanks for your help.
b.Fandango
I've been coding for about a day and I got this working beautifully using the third option I suggested in my question - old-school databound controls. Actually I only thought of the idea when I was forced to write out the question in detail - doesn't that just happen to you all the time?
I put my SearchCriterionControl into an asp:Repeater and bound it to my object collection. For the Field Chooser I put an asp:DropDownList inside a nested asp:Repeater and bound the Field array to that. Everything works beautifully, keeps state, actually required very little code. So I never had to dynamically add controls to the page, thank goodness.
Thanks for your suggestions, Ender, Matt and andrewWinn.
Since no one else has taken a stab at this for 2 hours, I'll throw my hat in the ring with a solution that does not rely on viewstate at all (or the ASP.NET model of postbacks).
What if you grabbed all the input values with jQuery and instead of doing a post-back did a post against the page (or a new results.aspx page)? Or, you could make the entire thing asyncrhonous and do an Ajax request against a web method, get fed the results, and populate on the client side as needed?
The unfortunate thing here is you have to reconstruct which type of controls were used to figure construct your search query since that data wont be passed with the viewstate. But I imagine you were already going to have to do some kind of translation of your input data into a query form anyway.
Read here for more information about using jQuery to hit an ASP.NET page method. Remember - page methods must be static (it's an easy oversight).
I'm not sure what you're doing server side to construct your query - but I would highly recommend LINQ. I did a similar "advanced search" function previously, and after a few different attempts found that LINQ was a wonderful tool for this problem, regardless of whether I was hitting SQL with LINQtoSQL or just hitting an in-memory collection of objects.
This worked so well because 1) LINQ is deferred execution and 2) A LINQ query returns another queryable object. The implication here is that you can chain your LINQ queries together as you construct them from your input, instead of having to do a single massive clause translation to SQL or whatever backstore you are using (one of my attempts was constructing SQL clauses with strings, but still passing input data via SQLParameters for SQL injection protection - it was messy and complicated when hand crafted LINQ was orders of magnitude easier to understand and implement).
For example:
List<string> data; // or perhaps your a DB Context for LINQtoSQL?
var query = data.Where(item => item.contains("foo"));
if( {user supplies length search option} )
query = query.Where(item => item.Length < 5);
// etc, etc.
// LINQ doesn't do anything until the query is iterated, at which point
// it will construct the SQL statement without you worrying about details or parameter binding
foreach(string value in query)
; // do something with the results
Because of deferred execution and the queryable return type, you can concatenate LINQ queries to this expression all day long and let it worry about the implementation details (such as converting to a SQL query) at execution time.
I can't provide you with the exact steps that you will need to do, but I HIGHLY suggest looking into asp.net page life cycle. I created a user control as a DLL one time. I had to capture postback data at specific steps in the lifecycle and recreate and rebind the data at other steps. Additionally thinkgs like viewstate are only available at certain points also. I know that I had to override On_init, On_prerender and some other methods.
Sorry I couldn't be more help, but I don't have the code with me (its with an old employer). I hope this helps.
If you are adding controls to the controls tree dynamically, you need to add them on postpack as well. Just call the method that builds the control on Page_Load or Page_Init and the controls should stay on the page on postback.
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.