Every time I click an ASP button on my page to select an item in my dropdown list, it is only choosing the first item in the list. It is as if every time I click a button the page refreshes and all variables reset. How do you choose an item from a dropdown when using dynamic data from a database?
This sounds indicative of populating the DropDownList in Page_Load. Is that the case? (I'm assuming you're using WebForms.) If you're populating the control in Page_Load then you'll want to wrap it in a conditional:
if (!IsPostBack)
{
// populate your controls from data
}
Otherwise, they'll get re-populated with each postback. When you click a button or perform some other action on the page which initiates a postback, Page_Load is called before the event handler. So in effect, this is happening:
User navigates to the page
Page_Load clears and re-populates the DropDownList
User chooses an item in the DropDownList
User clicks a button
Page_Load clears and re-populates the DropDownList
Button handler gets the current selection from the DropDownList, which is the default.
What do you mean by "click ASP button"?
If you are talking about the downarrow to open the dropdown list, then you need to set AutoPostback options to false if you don't want that opening the dropdown list triggers postback (that is on the other side required if you have any events related to the opening of your list).
Related
I have a c# dropdownlist inside a form. My goal is to hit a reset button and set the entire page back to the way it was when I first loaded the page. My textboxes are clear and everything is where it should be except my dropdownlist. It displays the last selected dropdownlist Item selected. I would like it to go back to the initial selection when I reload the page. How would I do this?
DropDownList1.ClearSelection();
or
DropDownList.Clear();
Doesn't work
DropDownList1.SelectedIndex= -1
I have a data grid that is created dynamically to display information retrieved from a database. The data grid consists of multiple bound columns and two button columns for each row, a view and a delete button.
Clicking either button calls the Page_Load() method with Page.IsPostBack as false.
if (!Page.IsPostBack)
{
this.bindForm(); // Populates drop down lists that the user can select
setAccess(false); // Sets access for the page
// Stuff commented out to avoid confusion
}
else
{
bindDynamicGrids(); // Create the data grid(s) and populate them
}
So when I first click the button the above code gets called with IsPostBack false, and the dynamic grids get bound. But, the button click event does not fire. When I click the button a second time, Page_Load is called with IsPostBack false, and after executing bindDynamicGrids() the button click event is fired. I cannot understand the difference between the first and second click.
I have read a few threads;
ASP.NET C#, need to press a button twice to make something happen
http://forums.asp.net/t/1783694.aspx?ASP+NET+Button+needs+to+be+clicked+twice
To attempt to understand the issue, but I must be missing something. From what I am gathering from the second link, a session variable may be getting set in the click event, which is also being set in Page_Load, and this is all an issue with ordering. If that is the case I am not seeing where it is happening.
When it is not a post back the bindForm() method is called, which populates all drop down lists. The edit click event populates those drop downs with the values from the row, but the click event is always a post back and the form has already been bound.
I have also considered having a script automatically double click one of the buttons anytime the user single clicks, but I have not been able to find an "OnClick" property for the column button. Any help that could be provided would be phenomenal.
The thing is, that the button click event happens after the Page_Load event meaning that the filtering does not get applied on the first postback. It has been updated on the second postback and you see the filtering.
You can try to move the code of your page_load event to OnPreRender so the reload happens after the button click event.
for more information look here: Button needs to be clicked twice
and here
I have a listview with a dropdown, with autopostback enabled.
The user can select yes - which postsback and brings up loads more dropdowns, no - which brings up a textbox, and blank - which does nothing.
As the original dropdownbox is databound it displays one of those values but at the moment always acts as if it was blank ie no other controls showing..
Can I make the page do ONE autopostback as soon as it's loaded without any user input to display the correct controls if it's a yes or no as opposed to blank?
try calling dropdownbox_selectedindexchanged(null,null) after binding in page load. it is just calling selectedindexchanged event programmatically. as far as i know you want to load controls based on dropdown selection when page first load and user haven't changed dropdown value. so this code will call it from code behind.
I have three user controls in one aspx page, where each user control is loading in each separate tabpanel.
Each usercontrol has gridivew and objectdatasource(which has selectmethods).
The gridview is binding data from the objectdatasource, on every postback.
I have some dropdowns, the selected values are passed to the objectdatasource on submit button click, which then populates the results in the gridview.
Now, if I click on any linkbutton on the gridview, the postback is happening and gridview is rebinding with null values, so no click event of linkbutton is happening.
Anybody can suggest me how to stop the postbacks for gridview. I tried placing the updatepanels but didnt help
You can control the flow of the program by checking IsPostback in Page_Load() and filling the grid only when it's supposed to be filled. You can also specify your UI elements to not postback as well, if certain ones are posting back when you don't want them to. Look into the AutoPostBack property.
If (IsPostBack == true) {
// do something, load that
}
Else {
// do something else, don't load that
}
Have a dropdown list with autopostback set to 'yes' have another dropdown list box that will be populated based on the selection of the first dropdown. It works fine until I put a submit botton on the form. When I do it appears to not do the auto postback until the submit button is pushed. Can you have a submit button on a form that has a dropdown with autopostback active. thanks...
Sure you can.
Are you handling the autopostback event of the first dropdown in the code-behind file to populate the second dropdown? If so, your postback event should be firing when you change your selection in the first dropdown. Put a breakpoint in your code to assure that your event code is being called.
Sure you can. Are you seeing it not load the second dropdown? If so, check where you're handling that, as it may be in the wrong spot (if you're doing it with code) or you might have it wrapped in a !postback without thinking about it. Post more code and explanation for more help.