Using a standard ASP.NET ListView with a LinqDataSource and pagination enabled (with a DataPager), what would be the best way to default to displaying the last page of results?
set the current page index to be the page count - 1.
You'll need to know the total record count and the number of records displayed on a page.
This helpful post shows you how to get the record count:
private LinqDataSourceSelectEventArgs args;
protected void LinqDataSource1_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
args = e;
e.Result = new Database().Table.Whatever...
}
protected void LinqDataSource1_Selected(object sender, LinqDataSourceStatusEventArgs e)
{
this.label1.Text = args.Arguments.TotalRowCount + " records";
}
There's further discussion there of a situation that sounds similar to yours.
I've never done this, but there are several places I would look to see if I could make the change you want: an OnSelecting handler for the data source, OnPreRender or OnDataBinding for the ListView, and OnPreRender for the DataPager. Essentially, you want to handle the case of !IsPostBack in a special way. I would probably look at the DataPager first and see if you can find out how many pages there are and set it to the last page. You may need to rebind the data source after setting the page to the one you want. After that I'd look at adding an OnDataBinding handler for the ListView and see what you can do there. I suspect that PreRender happens too late for the ListView to have any effect and OnSelecting, while good for filtering via a table-based function, probably won't do much good in this case.
Related
I have two RadioButtons on my Web Form and here is the code:
protected void RadioButton1_CheckedChanged(object sender, EventArgs e)
{
}
protected void RadioButton2_CheckedChanged(object sender, EventArgs e)
{
Response.Write(DateTime.Now.ToLongTimeString());
}
When I check RadioButton2, time appears on the page but when I check RadioButton1(RadioButton2 is unchecked now) it does not update the shown time and removes it.
the event function must be called when it checks and unchecks.I don't understand what is wrong here and why the time disappears
(As it is obvious, I know about GroupName property and AutoPostBack. My problem is something else)
You can check property of each control and check AutoPostBack=True
and also if checked="true"
I tried it on different ways and opened my pages with different browsers and I figured out a few things. the most important of them which is related to my problem:
When a control Calls back, the page refreshes and that is why the time disappears. It sends the status of all controls using post method to itself and they would be the same way as they were. But the time is not written on a control and it would not be saved.
As I said if it was for example on a Label, the text would be kept:
Label1.Text = DateTime.Now.ToLongTimeString();
It answers the first question but I still think that the event function must be called when the RadioButton is being unchecked.
I made researching about this subject I could not find proper answer.
In my default.aspx page, I have a treeview. Codes are in default.aspx like below:
protected void Page_Load(object sender, EventArgs e)
{
}
protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
{
Control ucont;
if (TreeView1.SelectedNode.Value == "Yeni Dönem")
{
ucont = LoadControl("usercontrols/yenidonem.ascx");
PlaceHolder1.Controls.Add(ucont);
}
else
{
ucont = LoadControl("usercontrols/tabloktar.ascx");
PlaceHolder1.Controls.Add(ucont);
}
}
I load user controls dnynmicaly. User controls are have button control. I can not fire user control's button click when I load it dynamcally. How can I solve this ?
Thanks.
First of all, I would not recommend adding control dynamically later than in Page_Load event. Other things to remember is that You should add it on each page load and assign unique ID value the control that does not change between postbacks.
In this case, the easiest way would be to always add both controls to the page and show appropriate one using Visibility property.
If that's not suitable for You, try to move the code from TreeView1_SelectedNodeChanged to the Page_Load event and load appropriate control on each postback until it should be changed to another one.
I haven't tested this, so if You have any issues when using thise answer, let me know in the comments and I'll try to help.
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.
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.