Web Forms :: How To Update Drop Down List Using Asynchronous Calls
Jan 7, 2011
I am currently developing a project management application using ASP.NET (VB). I am nearly done with it. But whenever users select an item from drop-down list control, a post back is triggered and screen is returned to the bagining. This is very irritating at times.
<p> So, I want to know how can I make partial postbacks so that page is not refreshed again and appropriate binding of list control with my oracle database is also made.
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Jan 7, 2011
I am currently developing a project management application using ASP.NET (VB). I am nearly done with it. But whenever users select an item from drop-down list control, a post back is triggered and screen is returned to the bagining. This is very irritating at times.
So, I want to know how can I make partial postbacks so that page is not refreshed again and appropriate binding of list control with my oracle database is also made.
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Sep 2, 2010
i have the code for asynchronous call to the database. i execute the sql command into the begin method that will executed onto the separate thread. now i want to execute the another database call asynchronously so that this also execute onto the separate thread. code for one database cal is here....
private SqlConnection con, con1;
private SqlCommand cmd, cmd1;
private SqlDataReader dr, dr1;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
AddOnPreRenderCompleteAsync(new BeginEventHandler(Begin),
new EndEventHandler(End)
);
}
}
/////////////BEGIN METHOD
IAsyncResult Begin(object sender, EventArgs e,AsyncCallback cb, object state)
{
string connect = "Data Source=.\SQLEXPRESS;Asynchronous Processing=true;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True";
con = new SqlConnection(connect);
con.Open();
cmd = new SqlCommand("SELECT FirstName,LastName,Age,Company,Profile FROM Person",con);
return cmd.BeginExecuteReader(cb, state);
}
//////END METHOD
void End(IAsyncResult ar)
{
dr = cmd.EndExecuteReader(ar);
Label2.Text = System.Threading.Thread.CurrentThread.GetHashCode().ToString();
GridView1.DataSource = dr;
GridView1.DataBind();
}
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Mar 12, 2010
I am relatively new to asp.net. In My asp.net website, i have a method GetData(int id) which is called Repetitively, depending on id count, GetData is desinged to get data from sharepoint and sql server both. if the Id count is high say =10, my page load time increases because GetData is called 10 times and the page load time keeps adding up. so I want to ask, is there any way that this GetData() be called asynchornously or by the use of some thread, so that my page loads faster.
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Nov 22, 2010
We have a custom Ajax checkbox control. In that control we set value (from inside the control) via a web service call (say WSCall1) to the business engine. There is also an event exposed on the OnClick of checkbox for the end user to have their custom code where the end user have their own web service call (say WSCall2). This event that end users will write is handled inside the ajax checkbox control on the "OnSuccess" of the internal web service call (i.e WSCall1) with an expectation that if WSCall1 succeeds, WSCall2 will get executed. This works fine with Firefox and Chrome but not in IE. In IE sometimes WSCall2 gets executed first and then WSCall1 -- actually there is no gurantee which web service gets called first. For WSCall1 we have used " Sys.Net.WebServiceProxy.invoke"
Is there a way we can make sure that WSCall2 gets only executed on the "OnSuccess" of WSCall1? Isn't the OnSuceess supposed to be executed when the WSCall1 thread returns?
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Sep 24, 2010
I have been moving my application to be more AJAX-based. Currently I have a web service call where I use jQuery to gather some textbox (string) and checkbox (boolean) results and pass it to a web service. Everything works really well, the response time is super quick. The only downside that I can see to this is
1) you need to use jQuery, which will add to the user's download time - this doesn't really affect my application too much because I am using jQuery throughout the site
2) users can see the code and potentially try to hack the web service because they know where it is
I am most concerned with #2. I've been reading a lot about .NET web service calls, using IAsyncResult,
http://msdn.microsoft.com/en-us/library/2e08f6yc.aspx, and I am beginning to understand the 4 methods available in this article. However, is there extra bloat using this way compared to the jQuery web service call?If there isn't that much bloat or lag time using this method, I'd like to convert my application. Which one of these 4 methods is best in a scenario where I am just returning a small string value? The 4 methods in the article are to wait for EndInvoke itself, which from what I read is not recommended because this may block the first thread; and this should not be used on a service that affects the UI.Create a WaitHandle to wait for the 'OK' before EndInvoke is called Poll the IAsyncResult for .IsCompleted, using sleep() and a Do While until IAsyncResult.IsCompleted is true, then call EndInvoke Pass a delegate function to BeginInvoke to be called once the operation is complete.
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Mar 30, 2010
I have a drop down list that has the initials of about 12 of our sales guys.How can I make it so that when they select their initials from the list, the next drop down list only shows their customers.In my database there is a column for customer name and salesman.
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Mar 30, 2010
I am using Visual Studio 2008 and created a simple ASPX page with two drop downs in it. I am using the Update Panel so that when any item is seleted in drop down 1 the second drop down selected item will change accordingly.
I was hoping the update panel will not fix the page refreshing but I am not sure what is wrong since I still see the Page refresh.
see the code below I am using.
[Code]....
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Oct 6, 2010
I have 2 dropdownlists, the second (department) cascades from the first (division). I use a jquery script to update the second drop down list. When the user clicks submit, the underlying model is updated, apart from the new value for department. 2 ideas I have for fixing this are; a) Generate a postback. Prefer not to do this because of bad user experience. b) With a JQuery change event, make a call to server side and set a ViewData variable that I can use to update the field in the model later.
However there must be a better way. This is the view;
<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/AdminAccounts.master"
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Mar 23, 2010
I have a user control in a master page with two drop down lists. When the user selects an item out of either ddl, I want to load a specific user control inside an update panel on the content page. I can't figure out how to get the user control to trigger the update panel.
Master
<%@ Register src="toolbar.ascx" tagname="toolbar" tagprefix="uc1" %>
<head id="Head1" runat="server">
</head>
<body>
[Code]....
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Mar 12, 2010
How can I have 2 Cascading Drop Down Lists for the same Drop Down List?here is my problemi have 3 drop down lists read from database1- Schools List 2- Classes List3- Teachers ListEvery School will have more than 1 Class and more than 1 TeacherWhat I want is when user select a School from Schools Drop Down List then BOTH (Classes and Teachers) should be refreshed based on the School Drop Down List
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Jan 25, 2011
OK Here is the situation:
I have a web app with a table of statistics on our salesmen's customers, and each row has a sparkline graph showing the general trend of the sales data for the last 12 months. Each page shows a particular salesman's customer list, and some of them can have an enormous number of customers = an enormous number of rows = an enormous number of sparklines (e.g. one in particular has 125 and takes 15 seconds to load).
For this reason, jQuery sparklines could not be used - they completely pinned the CPU of a user accessing a page with a lot of sparklines with IE.
So I moved on to using the Google Chart API, which worked much better, except for two issues: 1) it's on a secure site, and the Google Chart API URL is only served over HTTP (solved by using a small wrapper script to download the graph dynamically and re-serve it from our secure server); and 2) on a page with 125 sparklines, it was still very slow due to the number of requests (even when the 0-9 server prefixes are used to maximize the # of available connections).
So my next step beyond this was to try to make each of the "download/grab/re-serve image" method calls asynchronous - and it worked!
...but only on my dev box running in debug mode.
When I pushed it up to the live site, it was faster, but it left some of the images unloaded, which is of course unacceptable.
So here is what I was hoping some SO hotshot would know:
1) Why are my asynchronous method calls working while debugging, but not working on the live site?
2) Is there any easier way to get a large number of sparklines of some sort to load quickly on a secure server without making me want to tear my hair out?
2a.) Does anyone have any experience using the ASP.NET Chart Library? Is this something I should investigate?
2b.) A co-worker suggested I make my own sparkline routine using a 1x1 CSS background image and varying the height. The problems are a) it is completely un-extensible in case we want to make changes; b) it seems hacky as hell (leaves about a bajillion DIVs per sparkline in the markup); and c) I have no idea if it will be fast enough when there are 100-200 of them on one page - what are your thoughts on the feasibility of the 1x1 sprite approach?
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Aug 7, 2010
any modal popup controls whereas I can interact with the controls, causing callbacks and asynchronous calls without losing the popup.
I tried with the modalpopupextender, but the popup will disappear with the call and re-rendering the popup like many people will cause massive flashes of the popup which i want to try and avoid.
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Jan 5, 2010
Am using update panel in my .aspx page .when i change the value in drop down list inside the update panel am getting the following error. am not using any response object or server object in my code.
"Sys.WebForms.PageRequestManagerParserErrorException: The message received from the server could not be parsed. Common causes for this error ...."
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Jun 24, 2010
I have drop down list box that I would like to show two columns, is this possible? Or can it be done with a list box?The query correctly retrieves all of the table data to be displayed, one colum is an abbreviation, the other a bit longer description.
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Feb 6, 2010
I have the following Students class:
[Code]....
I need the 1 since it's a foreign key in another table. For the life of me, I can't get this to work like this.
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Jan 17, 2011
I've got a user control with a couple of buttons. Think of them as 'On' and 'Off'. When either button is clicked an async method is called. If the method is successful an event is fired. Within the event I want to update the enabled property of the two buttons so that only a single button is clickable at any one time. The problem is that any changes I make to the properties are not shown on screen because the postback is already complete. I tried wrapping the buttons in an UpdatePanel but I get an "Update method can only be called on UpdatePanel with ID 'xxxx' before Render' error. I understand why the problem occurs but I can't think of a solution.
Ideally what I'd like to do is simply call a method within the event that will update the UI, but I don't know if that's possible.
EDIT
Here's some example code. I can't post the exact code, but this explains the problem:
[Code]....
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Jul 2, 2010
I've the following doubt. I've a page "MyPage" and i've declared few dictionary objects in the page classMy doubt isIf i declare the dictionary as a private non-static object i'm not able to use it across the functions in that page class (the object is getting nulled)able to across the object across the functions. But will that object be same across all the users who have opened the page right now (guessing that each user will have an instance of the page in turn has an instance for the page class and static variables of a class are invariable across all the instances of the class
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Nov 10, 2010
I have a requirement in my application that, while saving the application, need to get all the value from drop down list and pass it to the view model. But application should not allow the user to select more than one item from drop down list manually, ie, only one value at a time. My view model is like ...
public class ListManagement
{
public IEnumerable<selectListItem> InactiveProduct { get; set; }
public string[] InactiveProductSelected { get; set; }
public IEnumerable<selectListItem> ActiveProduct { get; set; }
}
[code]...
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Mar 25, 2011
I am getting this error yet I know it to be untrue.This is the code:
ddlPartnerOrganisation.DataSource = agency.AgencyGetListOfEYDN();
string temp = ddlPartnerOrganisation.SelectedValue.ToString();
ddlPartnerOrganisation.DataValueField = "AgencyID"
;
ddlPartnerOrganisation.DataTextField = "AgencyName"
;
ddlPartnerOrganisation.DataBind();
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Jun 20, 2010
i have an instance of ObjectDataSource with specified update method. But on update i have an old values(previously set in gridview) in method - they are not updating.
<asp:ObjectDataSource ID="ObjectDataSource1" runat="server" DeleteMethod="DeletePayment"
InsertMethod="InsertPayment" SelectMethod="GetPayments" TypeName="CostsReportControl.Models.Payments"
UpdateMethod="UpdatePayment" OldValuesParameterFormatString="{0}_old">
<SelectParameters>
<asp:Parameter Direction="input" Type="string" Name="sortExpression" />
<asp:Parameter Direction="input" Type="string" Name="sortDirection" />
</SelectParameters>
<DeleteParameters>
<asp:Parameter Name="id" Type="Int32" />
</DeleteParameters>
</asp:ObjectDataSource>
<asp:ObjectDataSource ID="ObjectDataSource2" runat="server"
SelectMethod="GetList" TypeName="CostsReportControl.Models.PaymentTypes">
</asp:ObjectDataSource>
my update method
public void UpdatePayment(int Id,string Fullname,DateTime Date, string Sum, string PaymentType, string RecordInfo,int Id_old)
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Jul 29, 2010
i am confused about the fact that if partial update of dropdowns is possible through Update Panel ,then why we should use asp.net ajax Cascading drop down extender ,that has made same task bit complex by making callback to web services ? what is difference between using update panel and cascading drop down extender ?
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Aug 31, 2010
I have two drop down list on a page. The first one list projects and the second list users. The userlist is populated with an object datasourse that pulls a list of users for the selected Project.Whenever the Project list selection changes the second ddl Userlist always reverts to the first person in the list instead the person that was selected before a new Project was chosen.
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Jan 7, 2011
I am trying to create an MVC List View that can be filtered by the value selected from a drop down list.
Selecting a value should repost the page ... Since there is no concept of view state data I am having some issues with this ... I can get the repost to take place but my drop down resets and I am not able to get the value that was selected.
ASSET CONTROLLER:
[Code]....
[Code]....
I have tried many of the posts that refer to setting up drop down lists but can't set them up in the content because this is a List View.
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Mar 3, 2010
I have a Drop Down List which I need to bind to the database. Here is the situation. I am not using a SQLDataSource. It is built on the n-tier application. The datasource of the dropdown is referring to a method in the C#class. That method has a generic array list which populates information into the arraylist. The Arraylist is the parameter that is returned to the DropDown List.
I have also set the Text property of the Drop down list
Text='<%DataBinder.Eval(Container.DataItem,"Employee_ID")%>'>
However, it is not populating the DropDown list, what should I do?
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