I have an asp.net page with a list box on it. Multiple event handlers subscribe to its OnSelectedIndexChanged event.
When I change the SelectedIndex programmatically none of the events get fired.
Now a hack for this is to call each event handler, but this has already caused bugs since people didn't know they had to do this when adding a new event handler.
I can do this in a Winforms app and even when SelectedIndex is changed in code the events fire. Has anyone seen this before?
Take a look at the source code of the ListBox class and its base - ListControl. You will notice that the OnSelectedIndexChanged method is called from the RaisePostDataChangedEvent method. This means, that the SelectedIndexChanged event is only raised if the selected index was changed on the client side and the value stored in the ViewState does not equal data comes with the PostData. So, this event should not be raised if the SelectedIndex was changed in the server code.
As a workaround, I change data in database and complete events releated, then reload data with JavaScript.
Scenes: ASPxGridView control dtgRepair delete row, at the same time, ASPxComboBox value changed programmatically.
Server:
protected void dtgRepair_CustomCallback(object sender, ASPxGridViewCustomCallbackEventArgs e)
{
// update database here...
cmbMRType.SelectedIndex = 1;
dtgRepair.JSProperties["cpCallbackAction"] = "DeleteEntry";
}
Client:
function dtgRepair_EndCallback(s,e) {
if(cmbMRType.GetSelectedIndex() == 2 && dtgRepair.cpCallbackAction == "DeleteEntry" )
window.location.reload(true);
}
Related
in asp.net we can handle the RowDataBound event of the GridView control. this event fires when every row is added to the gridview.
i want to be able to handle this event in the gridview in a winforms application but i cannot find a similar event. my question is what is the event name that allows me to do the same as RowDataBound in asp.net?
The DataGridView doesn't have the same event handling as in ASP.NET.
What you could do is handle RowsAdded event, but note that more than one row can be added when this event fires. An example:
private void dataGridView1_RowsAdded(object sender, DataGridViewRowsAddedEventArgs e)
{
for (int i = e.RowIndex; i < e.RowCount + e.RowIndex; i++)
{
Console.WriteLine("Row " + i.ToString() + " added");
}
}
Also, this event is a bit 'buggy' - at the moment when it's databound it may fire more than once for each row, but afterwards it behaves correctly - when you add a new row to data source, it's fired only once.
But, I should probably mention (even if that's not your original question), that if you used this event in ASPX to handle output formatting, than here an equivalent would actually be CellFormatting event - this event is called whenever the cells needs to display it's value.
There's no exact counterpart of the RowDataBound event for the WinForms
DataGridView. But if you'd like to change the displayed text before the
value of a cell is rendered, you could handle the CellFormatting event of
the DataGridView .
I have a GridView with dynamically created image buttons that should fire command events when clicked. The event handling basically works, except for the very first time a button is clicked. Then, the postback is processed, but the event is not fired.
I have tried to debug this, and it seems to me, that the code executed before and after the first click is exactly the same as for any other clicks. (With the exception that in the first click, the event handler is not called.)
There is some peculiarity in that: The buttons which fire the event are created dynamically through databinding, i.e. databinding must be carried out twice in the page lifecycle: Once on load, in order to make the buttons exist (otherwise, events could not be handled at all), and once before rendering in order to display the new data after the events have been processed.
I have read these posts but they wouldn't match my situation:
ASP.NET LinkButton OnClick Event Is Not Working On Home Page,
LinkButton not firing on production server,
ASP.NET Click() event doesn't fire on second postback
To the details:
The GridView contains image buttons in each row. The images of the buttons are databound. The rows are generated by GridView.DataBind(). To achieve this, I have used the TemplateField with a custom ItemTemplate implementation. The ItemTemplate's InstantiateIn method creates the ImageButton and assigns it the according event handler. Further, the image's DataBinding event is assigned a handler that retrieves the appropriate image based on the respective row's data.
The GridView is placed on a UserControl. The UserControl defines the event handlers for the GridView's events. The code roughly looks as follows:
private DataTable dataTable = new DataTable();
protected SPGridView grid;
protected override void OnLoad(EventArgs e)
{
DoDataBind(); // Creates the grid. This is essential in order for postback events to work.
}
protected override void Render(HtmlTextWriter writer)
{
DoDataBind();
base.Render(writer); // Renews the grid according to the latest changes
}
void ReadButton_Command(object sender, CommandEventArgs e)
{
ImageButton button = (ImageButton)sender;
GridViewRow viewRow = (GridViewRow)button.NamingContainer;
int rowIndex = viewRow.RowIndex;
// rowIndex is used to identify the row in which the button was clicked,
// since the control.ID is equal for all rows.
// [... some code to process the event ...]
}
private void DoDataBind()
{
// [... Some code to fill the dataTable ...]
grid.AutoGenerateColumns = false;
grid.Columns.Clear();
TemplateField templateField = new TemplateField();
templateField.HeaderText = "";
templateField.ItemTemplate = new MyItemTemplate(new CommandEventHandler(ReadButton_Command));
grid.Columns.Add(templateField);
grid.DataSource = this.dataTable.DefaultView;
grid.DataBind();
}
private class MyItemTemplate : ITemplate
{
private CommandEventHandler commandEventHandler;
public MyItemTemplate(CommandEventHandler commandEventHandler)
{
this.commandEventHandler = commandEventHandler;
}
public void InstantiateIn(Control container)
{
ImageButton imageButton = new ImageButton();
imageButton.ID = "btnRead";
imageButton.Command += commandEventHandler;
imageButton.DataBinding += new EventHandler(imageButton_DataBinding);
container.Controls.Add(imageButton);
}
void imageButton_DataBinding(object sender, EventArgs e)
{
// Code to get image URL
}
}
Just to repeat: At each lifecycle, first the OnLoad is executed, which generates the Grid with the ImageButtons. Then, the events are processed. Since the buttons are there, the events usually work. Afterwards, Render is called, which generates the Grid from scratch based upon the new data. This always works, except for the very first time the user clicks on an image button, although I have asserted that the grid and image buttons are also generated when the page is sent to the user for the first time.
Hope that someone can help me understand this or tell me a better solution for my situation.
A couple problems here. Number one, there is no IsPostBack check, which means you're databinding on every load... this is bound to cause some problems, including events not firing. Second, you are calling DoDataBind() twice on every load because you're calling it in OnLoad and Render. Why?
Bind the data ONCE... and then again in reaction to events (if needed).
Other issue... don't bind events to ImageButton in the template fields. This is generally not going to work. Use the ItemCommand event and CommandName/CommandArgument values.
Finally... one last question for you... have you done a comparison (windiff or other tool) on the HTML rendered by the entire page on the first load, and then subsequent loads? Are they EXACTLY the same? Or is there a slight difference... in a control name or PostBack reference?
Well I think the event dispatching happens after page load. In this case, its going to try to run against the controls created by your first data-binding attempt. This controls will have different IDs than when they are recreated later. I'd guess ASP.NET is trying to map the incoming events to a control, not finding a control, and then thats it.
I recommend taking captures of what is in the actual post.
ASP.NET is pretty crummy when it comes to event binding and dynamically created controls. Have fun.
Since in my opinion this is a partial answer, I re-post it this way:
If I use normal Buttons instead of ImageButtons (in the exact same place, i.e. still using MyItemTemplate but instantiating Button instead of ImageButton in "InstantiateIn", it works fine.
If I assert that DoDataBind() is always executed twice before sending the content to the client, it works fine with ImageButtons.
Still puzzled, but whatever...
I renew parameters of my DataSource for GridView on Button and loads event Page_Load()
and After it (or with it) GridView renews itself.
I need to rename Header rows but there is no event after Page Load.
more information about details here :
[On Button Click] I change DataSource and Bind it (SqlDataSource1.DataBind(); ) Then sure Page gone to Refresh elements.
[On Page_Load] GridView is changing data, but if I can't change Headers there because it's looking like loads after this function :(
[one more Button] I can add new button with a function - rename headers and it works correct everytime
protected void Button2_Click(object sender, EventArgs e)
{
// Stack overflow
DataRow T;
if (go)
if (GridView2.HeaderRow.Cells.Count != 0)
for (int i = 0; i < SQF.SQF.Permission.Rows.Count; i++)
{
T = SQF.SQF.Permission.Rows[i];
GridView2.HeaderRow.Cells[i].Text = (string)T["Caption1"];
WebMsgBox.Show((string)T["Caption1"]);
}
}
Trouble : I no need one more button for it, I need to rename header rows after I click button to change Data but I have no idea where I can do it.
thank you.
Well you could use Gridview DataBound event, like that:
<asp:GridView runat="server" ID="SomeID" OnDataBound="GridVIew_OnDataBound" ... />
The DataBound event occurs right after the databinding process for that particular control has completed.
After Page_Load there is an event Page.PreRender.
Maybe it will suit you.
EDIT.
All events of your components, such as GridView, are fired between Page.Load and Page.PreRender. Consider using RowDataBound and RowUpdated events.
I have a web user control (ascx) that exposes an "ID" property. What I want to do is set this property when the SelectedIndexChanged event fires in a gridview in the containing page. However, I can't seem to do it.... Here's my code:
protected void grdPhysicians_SelectedIndexChanged(object sender, EventArgs e)
{
physicians_certif1.mdID = grdPhysicians.SelectedDataKey.ToString();
mvData.SetActiveView(viewEdit);
panAdditional.Visible = true;
}
Physicians_certif1 is the user control. It seems the user control is loading before the SelectedIndexChanged event has a chance to set it's property.
Any ideas folks?
ASP.Net page lifecycles can be hard to understand especially with ascx user controls which also have their own lifecycle. If you are setting the mdID property in Page_Load of either the page or the ASCX control or have hardcoded a default value into it in the XHTML, it is probably being reset after SelectedIndexChanged fires.
Set a breakpoint in grdPhysicians_SelectedIndexChanged, set a watch on physicians_certif1.mdID and step through the code using the debugger.
Yes, that is exactly what is happening. You should look at (and be familiar with) the following resource:
ASP.Net Page Life Cycle
The page will load, then the control will load, then your events will begin to fire. If you have configuration needs based on event triggers, it is best either to place those configurations in the Page_LoadComplete or Page_PreRender events of the user control in question or apply "Rebinding" instructions in the Set method of your property:
public MyValue MyProperty()
{
get
{
return _myProperty;
}
set
{
RebindMyControls();
_myProperty = value;
}
}
Here's the scenario:
-Gridview control
-Calendar control
I only want the calendar to show if a specific item is chosen in the drop down list which is in a gridview. When the grid view row is updated I want to change whether or not the calendar is visible. The calendar's visibility only shows correctly on the next post back.
Page_Load is called before events which are called before Render. There is no reason why you couldn't, in your event, check the value of the dropdownlist and set the Calendar control visible property, this would then knock into Render.
Try adding a check of IsPostBack before setting the loading your GridView. That will prevent you from overwriting it's values.
protected void Page_Load(object sender, EventArgs e) {
if(!IsPostBack) {
/*Populate your GridView*/
}
}
protected void GridView_RowUpdated(object sender, GridViewUpdatedEventArgs e)
{
/*show your calendar here if you need to*/
if(whatever) calendar.Visible = true;
}
This should work, if it doesn't then I'd recommend putting breakpoints in your Page_Load and RowUpdated methods and stepping through it, preferrably with a Watch on the gridview's datasource (it'll go red if it's changed) and a watch on calendar.Visible, to help you see if something has changed.
For the record, control events like OnRowUpdated will never fire before Page_Load unless explicitly called for some reason. Chances are you're just doing something where it's not updating the content of the GridView before it gets to the RowUpdated method, or it's overwriting the data in the GridView due to a lack of !IsPostBack check.