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.
Related
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...
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.
Using VS2005, ASP.Net 2.0, AjaxControlToolKit
I have a LinkButton in a Panel that contains an UpdatePanel with a GridView. The link button is outside the UpdatePanel. The OnClick event has this code:
protected void lnkOk_Click(object sender, EventArgs e)
{
foreach (GridViewRow row in grdProductSearch.Rows)
{
CheckBox chk = row.Cells[0].Controls[0] as CheckBox;
if (chk != null && chk.Checked)
{
// ...
}
}
Server.Transfer(Page.Request.RawUrl);
}
I need it to pass the selected values of the grid back to the Parent page in a post back. But all it does is close the Panel.
Any ideas why this is happening? or how can I achieve what I am trying to do?
Try putting everything inside the UpdatePanel. Sometimes this control messes up the page normal behavior.
I've seen several times that UpdatePanel control affect somehow (it's difficult to say where and how) the javascript of the page. For example, When you have the UpdatePanel declared as ChildrenAsTriggers="false" and declared AsyncPostBack triggers, if you have a Validation Summary inside, it never shows the validation errors done in the server.
I read about the dynamic control creation in ASP.NET this piece of text:
...When using dynamic controls, you
must remember that they will exist
only until the next postback. ASP.NET
will not re-create a dynamically added
control. If you need to re-create a
control multiple times, you should
perform the control creation in the
Page.Load event handler. This has the
additional benefit of allowing you to
use view state with your dynamic
control. Even though view state is
normally restored before the Page.Load
event, if you create a control in the
handler for the Page.Load event,
ASP.NET will apply any view state
information that it has after the
Page.Load event handler ends. This
process is automatic ...
I wanted to try it on example
create a button declaratively -
<asp:Button ID="Button1" runat="server" Text="Button"
onclick="Button1_Click" />
and dynamically on behind code 5 checkboxes -
protected void Page_Load(object sender, EventArgs e)
{
for (int i = 0; i <= 5; i++)
{
var chBox = new HtmlInputCheckBox();
Controls.Add(chBox);
}
}
But when i check some checkboxes and hit the button, after postback all checkboxes
states are erased. It mean ASP.NET does not manage view states of dynamic controls
automatically? I tried to enable view state to each of checkbox and for whole page,
but its doesn't work.
Can someone explain:
1. Why is it so?
2. How to avoid this?
The reason this is happening is because in order for ASP.NET to restored POSTed values, those controls need to be a part of the page before Load. In order to make this work you need to (if possible) create your controls OnInit of the page.
The controls can be created on Page_Init.
protected void Page_Init(object sender, EventArguments e)
{
//Generate the checkboxes dynamically here.
CheckBox c;
for (int i = 0; i < 5; i++) {
c = new CheckBox();
c.ID = "Checkbox" + i.ToString();
divContainer.Controls.Add(c); //create a div with runat="Server" attribute or use an asp:Panel, etc. container controls.
}
}
After that, try clicking the button again, the state will be always be maintained.
You must set an ID for each dynamic control so that they can be synchronized across postbacks.
As I understand - there is no matter where to create controls in OnInit or OnLoad
(but some books suggests in onLoad), the matter is where to place them - if
you place through Controls.Add - it place them out of <form></form> so postback
does not takes control's states. after cretating a placeholder inside <form></form> and add dynamic controls to this placeholder everthing start to work fine.
I have a ASP.NET GridView that uses template columns and user controls to allow me to dynamically construct the datagrid. Now I'm implementing the event handler for inserting a row. To do that, I create an array of default values and add it to the data table which is acting as a data source. However, when my OnLoad event is fired on postback, all my template columns no longer have the user controls. My gridview ends up just being all blank with nothing in it and my button column disappears as well (which contains the add row, delete row and save buttons).
My row add event just does this:
public void AddDataGridRow()
{
List<object> defRow = new List<object>();
for (int i = 0; i < fieldNames.Count; i++)
{
defRow.Add(GetDefaultValueFromDBType(types[i]));
}
dt.Rows.Add(defRow);
}
It is fired from a button in a user control that's implement like this:
protected void Button1_Click(object sender, EventArgs e)
{
((Scoresheet)(this.Page)).AddDataGridRow();
}
My on load event does a bunch of stuff on first run to set the GridView up but I don't run that again by using the IsPostBack property to tell.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
Initialize();
}
Anyone have any hints as to why my user controls are vanishing?
You have to add the controls to the grid on every page_load, not just if it's (!Postback)
Do you have the EnableViewState=true on the usercontrols and the GridView?
Is the AddDataGridRow() method called by Initialize()? You basically have two options:
Bind the grid on every postback and do not use viewstate (performace loss)
Bind the Grid only the first time (if (!IsPostBack)), and make sure that your user controls keep their viewstate.
From your code, it is not clear whether the user controls keep viewstate and what they have in them. It is not even clear what is the execution order of the methods you've shown. There is no binding logic, so even if you keep adding rows, the grid may still not be bound. Please elaborate a bit and show the whole page codebehind.