here is an example of what I am doing
Page Load
{
//Adds items to a panel (not an updatepanel just a normal panel control)
}
protected void btnNexMod_Click(object sender, EventArgs e)
{
// Calls DoWork() and Appends more items to the same panel
}
My problem is that the asp:button is doing a postback as well as calling DoWork()
Therefore, re-calling my page load, re-initializing my panel :(
I want my items that I have added to the panel to stay there!
All help appreciated, not looking for a hand you the answer kind-of deal. Any steps are appreciated thanks!
Here is an exact example of my problem.
protected void Page_Load(object sender, EventArgs e)
{
CheckBox chkbox = new CheckBox();
chkbox.Text = "hey";
chkbox.ID = "chk" + "hey";
// Add our checkbox to the panel
Panel1.Controls.Add(chkbox);
}
protected void Button1_Click(object sender, EventArgs e)
{
CheckBox chkbox = new CheckBox();
chkbox.Text = "hey";
chkbox.ID = "chk" + "hey";
// Add our checkbox to the panel
Panel1.Controls.Add(chkbox);
}
Only thing on the page is a empty panel and a button with this click even handler.
I have also tried this and it still doesn't work. Now its clearing the initial item appended to the panel.
if (!Page.IsPostBack) // to avoid reloading your control on postback
{
CheckBox chkbox = new CheckBox();
chkbox.Text = "Initial";
chkbox.ID = "chk" + "Initial";
// Add our checkbox to the panel
Panel1.Controls.Add(chkbox);
}
If you're adding controls to the Panel dynamically, then you'll have to recreate the controls at every postback, and make sure to assign the same IDs to the controls so that ViewState can populate the values. It's usually best to recreate dynamic content during OnInit, but this can be difficult in some situations.
One of my favorite tools is the DynamicControlsPlaceHolder, because you can add dynamic controls to it and it will persist them automagically, without any additional coding required on the page. Just add controls to it, and it will do the rest.
Here's the link:
http://www.denisbauer.com/Home/DynamicControlsPlaceholder
As for preventing your button from performing a postback, use OnClientClick and return false.
OnClientClick="return false;"
You could use
<asp:LinkButton OnClientClick="javascript:addItemsToPanel();return false;"
thus using a javascript function to add them. That's how I've got around that problem.
You can also try this:
Page Load
{
if (!this.IsPostBack) // to avoid reloading your control on postback
{
//Adds items to a panel (not an updatepanel just a normal panel control)
}
}
you can do like this...
ASPX code:
<asp:LinkButton ID="someID" runat="server" Text="clicky"></asp:LinkButton>
Code behind:
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
someID.Attributes.Add("onClick", "return false;");
}
}
What renders as HTML is:
<a onclick="return false;" id="someID" href="javascript:__doPostBack('someID','')">clicky</a>
You are correct, you will have to add the new items to the Panel after a PostBack. That is the nature of the .NET pipeline.
If you use a data bound control, like a Repeater, to display the panel contents, then the button click handler just needs to rebind the control and it will all work out correctly.
Changing the asp:Button to a asp:LinkButton solved my issue.
I think, it is better use the Ajax Update panel. And put your button in to that.
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button1" />
</ContentTemplate>
</asp:UpdatePanel>
Related
I have this button in my aspx file.
<telerik:RadButton ID="btnEnable" OnClick="btnEnable_Click" runat="server" ToolTip="enable"
Text="Enable" Enabled="false" Icon-PrimaryIconUrl="~/images/icon.png">
</telerik:RadButton>
I am disabling it on client-side like this :
btnEnable.set_enabled(false);
I want to add server-side code in my aspx.cs. So when item is selected in grid, I want this button to be disabled from server-side.
function looks like this
protected void btnEnable_Click(object sender, EventArgs e)
{
if(someLogic){btnEnable must be disabled}
}
If it helps, this button can be called after item is selected in the grid.
Remember you can add ToggleStates:
MyButton.ToggleType = ButtonToggleType.CheckBox;
MyButton.ButtonType = RadButtonType.ToggleButton;
MyButton.ToggleStates.Add("Selected");
MyButton.ToggleStates.Add("Unselected");
MyButton.Checked= false; //set to unselected
Lets preface this with the fact that I am learning ASP.NET C# and this is my first "real" project so there is a good chance I am missing something obvious, I apologize in advance.
I am working on a web page that displays three columns. The first is "Categories", a user should be able to select a category then have a list of items to choose from appear in the second column "Items". When they click an item the third column should show details about said item. For the most part this is a classic Master/Detail scenario except we take it a step further and do Master/Detail/Detail.
To achieve this I am generating dynamic buttons on Page_Load() in the "Categories" column. In addition I have added a debug line when the page loads, this is important later.
protected void Page_Load(object sender, EventArgs e)
{
//DB query to get categories omitted
for (int i = 0; i < categories.Rows.Count; i++)
{
Button btn = new Button();
btn.Click += new System.EventHandler(CategorySelected_Click);
btn.Attributes["runat"] = "server";
btn.ID = "CatSelBtn" + i;
btn.Attributes["data-categoryid"] = qry.GetCategories().Rows[i]["id"].ToString();
//And some other non-relevant attributes
CategoriesPane.Controls.Add(btn);
}
System.Diagnostics.Debug.WriteLine("Page Loaded");
}
As you may have noticed these buttons have a Click event handler that calls the method CategorySelected_Click(). These buttons all generate successfully and clicking on them results in that method being successfully called. This method is set up in a similar fashion, it grabs a list of items then generates buttons for the items, of course this needs to be done asynchronously so it doesn't reset the user's category selection, so this time it is all contained with an update panel.
C#
protected void CategorySelected_Click(object sender, EventArgs e)
{
//DB query to get items omitted
Button btn = (sender as Button);
string categoryid = btn.Attributes["data-categoryid"].ToString();
for (int i = 0; i < items.Rows.Count; i++)
{
if (items.Rows[i]["Category"].ToString() == categoryid)
{
Button ibtn = new Button();
ibtn.Click += new System.EventHandler(this.ItemSelected_Click);
ibtn.Attributes["runat"] = "server";
ibtn.ID = "ItmSelBtn" + i;
ibtn.Attributes["data-itemid"] = qry.GetItems().Rows[i]["id"].ToString();
//And again some none relevant attributes here
ItemsParent.Controls.Add(ibtn);
}
}
ItemsPanel.Update();
}
ASP
<div class="col-md-2 items-pane">
<asp:UpdatePanel ID="ItemsPanel" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="False">
<ContentTemplate>
<div id="ItemsParent" runat="server">
</div>
</ContentTemplate>
</asp:UpdatePanel>
</div>
<div class="col-md-8 view-pane">
<asp:UpdatePanel ID="ItemDetailsPanel" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="False">
<ContentTemplate>
<div id="ItemDetailsParent" runat="server">
</div>
</ContentTemplate>
</asp:UpdatePanel>
</div>
Again this generates a list of buttons for each item matching the correct category. No issue there, but this time I need the clicked button to call the third and final method which will display the details for the item. This is where things stop working. I assumed that because I was able to generate buttons successfully on Page_Load() that it would work the same inside an update panel. Right now the third method just contains a debug line to check if its firing at all.
protected void ItemSelected_Click(object sender, EventArgs e)
{
System.Diagnostics.Debug.WriteLine("Item has been selected");
ItemDetailsPanel.Update();
}
In my output console in visual studio when I click on an Item Button control it writes Page Loaded indicating a successful postback but I am not seeing Item has been selected indicating that the third method is firing. I also inserted a breakpoint there but it is not being reached.
I initially thought I needed to add an asyncpostback trigger for each button generated to my update panel but that did not seem to resolve that issue, and because I can now see that Page_Load() is getting triggered I am pretty sure that isn't the issue. This leads me to believe that the click event is somehow not being registered. So my question to you is this: How do I make a dynamically generated button inside an update panel call a server side method? Any help is greatly appreciated.
You need to attach the event handlers on every postback.
It works for your categories-buttons, because the attaching is executed on every page load.
Do this for all the other items also, e.g. put in your Page_Load something like this:
foreach (var ctrl in ItemsParent.Controls)
{
Button ibtn = ctrl as Button;
if (ibtn != null)
{
ibtn.Click += new System.EventHandler(this.ItemSelected_Click);
}
}
I have an anchor on Lable Text.I am creating anchor with runat="server" dynamically on click of a button, It gets created as expected. I want to use its click event but it does not fire.
My code :
lblEmail.Text = email + " <a href='#' runat='server' class='crossicon' onclick='removebtn_Click'></a> ";
protected void removebtn_Click(object sender, EventArgs e)
{
}
How Can I create event for this button?I don't want to use JS, as in that case I will have to use a hidden field for new value
Adding markup/text to the label in that way wouldn't add the linkbutton or register the event to the control tree at the server. For that behavior of dynamically adding controls along with the server events to be achieved, you need to register the controls and events (as shown below)
aspx:
<asp:Panel runat="server" id="pnlEmail">
<asp:Label runat="server" id="lblEmail"/>
</asp:Panel>
aspx.cs:
In whichever event, you want to set the label text (along with the link)
lblEmail.Text = email;
LinkButton lnkbtnEmail = new LinkButton();
lnkbtn.Click += lnkbtn_Click;
lnkbtn.Text = "Dynamic Link";
pnlEmail.Controls.Add(lnkbtnEmail);
And the Handler would be
void lnkbtn_Click(object sender, EventArgs e)
{
// code for your dynamically generated link
}
By default, controls use __doPostBack to do the postback to the server. __doPostBack takes the UniqueID of the control (or in HTML, the name property of the HTML element). The second parameter is the name of the command to fire.
<a href='#' runat='server' class='crossicon' href="javascript:void(0);" onclick="__doPostBack('someuniqueid', '');></a>
System.Web.UI.Page already implements the IPostBackEventHandler interface by default, so you don't need to implement it on every page - it's already there.
You can override the RaisePostBackEvent method on the page like this:
protected override void RaisePostBackEvent(IPostBackEventHandler source, string eventArgument)
{
//call the RaisePostBack event
base.RaisePostBackEvent(source, eventArgument);
if (source == SomeControl)
{
//do something
}
}
I hope it will help you.
I don't think so it is created dynamically. Where is ID of that control. You have to Create Server side control and add it into some placeholder/panel e.t.c
I am dynamically adding a custom user control to an update panel. My user control contains two dropdownlists and a textbox. When a control outside of the update panel triggers a postsback, I am re-adding the user control to the update panel.
The problem is...on postback when I re-add the user controls, it's firing the "SelectedIndexChanged" event of the dropdownlists inside the user control. Even if the selectedindex did not change since the last postback.
Any ideas?
I can post the code if necessary, but there's quite a bit in this particular scenario.
Thanks in advance!
EDIT...CODE ADDED BELOW
*.ASCX
<asp:DropDownList ID="ddlColumns" OnSelectedIndexChanged="ddlColumns_SelectedChanged" AppendDataBoundItems="true" AutoPostBack="true" runat="server">
*.ASCX.CS
List<dataColumnSpecs> dataColumns = new List<dataColumnSpecs>();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
fillDDLColumns();
}
}
public void fillDataColumnsList()
{
dataColumns.Clear();
//COMMON GETDATATABLE RETURNS A DATA TABLE POPULATED WITH THE RESULTS FROM THE STORED PROC COMMAND
DataTable dt = common.getDataTable(storedProcs.SELECT_COLUMNS, new List<SqlParameter>());
foreach (DataRow dr in dt.Rows)
{
dataColumns.Add(new dataColumnSpecs(dr["columnName"].ToString(), dr["friendlyName"].ToString(), dr["dataType"].ToString(), (int)dr["dataSize"]));
}
}
public void fillDDLColumns()
{
fillDataColumnsList();
ddlColumns.Items.Clear();
foreach (dataColumnSpecs dcs in dataColumns)
{
ListItem li = new ListItem();
li.Text = dcs.friendlyName;
li.Value = dcs.columnName;
ddlColumns.Items.Add(li);
}
ddlColumns.Items.Insert(0, new ListItem(" -SELECT A COLUMN- ", ""));
ddlColumns.DataBind();
}
protected void ddlColumns_SelectedChanged(object sender, EventArgs e)
{
//THIS CODE IS BEING FIRED WHEN A BUTTON ON THE PARENT *.ASPX IS CLICKED
}
*.ASPX
<asp:UpdatePanel ID="upControls" runat="server">
<ContentTemplate>
<asp:Button ID="btnAddControl" runat="server" Text="+" OnClick="btnAddControl_Click" />
</ContentTemplate>
</asp:UpdatePanel>
<asp:Button ID="btnGo" runat="server" Text="Go" OnClick="btnGo_Click" ValidationGroup="vgGo" />
<asp:GridView...
*.ASPX.CS
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
uc_Counter = 0;
addControl();
gridview_DataBind();
}
else
{
reloadControls();
}
}
protected void btnGo_Click(object sender, EventArgs e)
{
if (Page.IsValid)
{
//THIS BUTTON CLICK IS WHAT'S TRIGGERING THE
//SELECTEDINDEXCHANGED EVENT TO FIRE ON MY *.ASCX
gridview_DataBind();
}
}
private void reloadControls()
{
int count = this.uc_Counter;
for (int i = 0; i < count; i++)
{
Control myUserControl = Page.LoadControl("~/Controls/myUserControl.ascx");
myUserControl.ID = "scID_" + i;
upControls.ContentTemplateContainer.Controls.AddAt(i, myUserControl);
((customUserControl)myUserControl).fillDDLColumns();
}
}
private void addControl()
{
Control myUserControl = Page.LoadControl("~/Controls/myUserControl.ascx");
myUserControl.ID = "scID_" + uc_Counter.ToString();
upControls.ContentTemplateContainer.Controls.AddAt(upControls.ContentTemplateContainer.Controls.IndexOf(btnAddControl), myUserControl);
//((customUserControl)myUserControl).fillDDLColumns();
this.uc_Counter++;
}
protected int uc_Counter
{
get { return (int)ViewState["uc_Counter"]; }
set { ViewState["uc_Counter"] = value; }
}
Even though this is already answered I want to put an answer here since I've recently tangled with this problem and I couldn't find an answer anywhere that helped me but I did find a solution after a lot of digging into the code.
For me, the reason why this was happening was due to someone overwriting PageStatePersister to change how the viewstate hidden field is rendered. Why do that? I found my answer here.
One of the greatest problems when trying to optimize an ASP.NET page to be more search engine friendly is the view state hidden field. Most search engines give more score to the content of the firsts[sic] thousands of bytes of the document so if your first 2 KB are view state junk your pages are penalized. So the goal here is to move the view state data as down as possible.
What the code I encountered did was blank out the __VIEWSTATE hidden fields and create a view_state hidden field towards the bottom of the page. The problem with this is that it totally mucked up the viewstate and I was getting dropdownlists reported as being changed when they weren't, as well as having all dropdownlists going through the same handler on submit. It was a mess. My solution was to turn off this custom persister on this page only so I wouldn't have to compensate for all this weirdness.
protected override PageStatePersister PageStatePersister
{
get
{
if (LoginRedirectUrl == "/the_page_in_question.aspx")
{
return new HiddenFieldPageStatePersister(Page);
}
return new CustomPageStatePersister(this);
}
}
This allowed me to have my proper viewstate for the page I needed it on but kept the SEO code for the rest of the site. Hope this helps someone.
I found my answer in this post .net DropDownList gets cleared after postback
I changed my counter that I was storing in the viewstate to a session variable.
Then I moved my reloadControls() function from the Page_Load of the *.ASPX to the Page_Init.
The key was dynamically adding my user control in the Page_Init so it would be a member of the page before the Viewstate was applied to controls on the page.
I am trying to create a UI that creates rows that can be dynamically populated.
I am at the point where I can add a Panel to my list that contains a DropDownList and has an associated Remove Button.
The Remove Button has an OnClick event bound that allows me to remove that specific panel.
I am having an issue when trying to bind a SelectedIndexChanged EventHandler to my DropDownList it does not.
I suspect this had something to do with how I am recreating my controls after every Postback.
I am not asking for or expecting a straightforward "Add this or Change this in the code." I really want to have a understand where I am going wrong, sorry for asking so much! :s
protected void Page_Load(object sender, EventArgs e)
{
//Showing this for the the poster that asked.
if (!IsPostBack)
{
GetClustersFromDB(user);
BindGrid();
BindState();
}
if (Session["persistControls"] != null)
{
persistControls = (List<Panel>)Session["persistControls"];
int count = 0;
foreach (Panel dynamicControl in persistControls)
{
DropDownList list = new DropDownList();
list.ID = "list" + count;
list.SelectedIndexChanged += new EventHandler(list_SelectedIndexChanged);
list.AutoPostBack = true;
list.Items.Add(new ListItem("", "0"));
list.Items.Add(new ListItem("Title", "1"));
dynamicControl.ID = "panel" + count;
Button btnRemove = new Button();
btnRemove.Click += new EventHandler(btnDelete_Click);
btnRemove.Text = "Remove";
btnRemove.CommandArgument = count.ToString();
myPlaceholder.Controls.Add(dynamicControl);
myPlaceholder.Controls.Add(btnRemove);
count++;
}
}
}
protected void btnAdd_Click(object sender, EventArgs e)
{
try
{
DropDownList list = new DropDownList();
list.SelectedIndexChanged += new EventHandler(list_SelectedIndexChanged);
list.AutoPostBack = true;
list.Items.Add(new ListItem("", "0"));
list.Items.Add(new ListItem("Title", "1"));
Panel panelContainer = new Panel();
panelContainer.ID = "panel" + persistControls.Count;
panelContainer.Controls.Add(list);
Button btnRemove = new Button();
btnRemove.Click += new EventHandler(btnDelete_Click);
btnRemove.Text = "Remove";
btnRemove.CommandArgument = persistControls.Count.ToString();
myPlaceholder.Controls.Add(panelContainer); // Pushes the Panel to the page.
persistControls.Add(panelContainer);// Adds our Panel to the Control list
myPlaceholder.Controls.Add(btnRemove); // Pushes our Button to the page.
Session["persistControls"] = persistControls; // put it in the session
}
catch
{
throw;
}
}
protected void btnDelete_Click(object sender, EventArgs e)
{
try
{
int deleteThisOne = int.Parse(((Button)sender).CommandArgument);
persistControls.Remove(persistControls[deleteThisOne]);
Session["persistControls"] = persistControls;
Response.Redirect(Request.Url.ToString());
}
catch
{
throw;
}
}
protected void list_SelectedIndexChanged(object sender, EventArgs e)
{
throw new NotImplementedException();
}
//aspx File Snippets
<asp:Button ID="btnAdd" runat="server" Text="Add Control" onclick="btnAdd_Click" />
<asp:Button ID="btnClear" runat="server" Text="Reset" onclick="btnClear_Click"/>
<asp:PlaceHolder ID="myPlaceholder" runat="server"></asp:PlaceHolder>
Maintaining controls like this is a real pain. You could try an alternative approach:
Create a (small) class that encapsulates the data you want to display in each Panel.
Maintain a List of these objects in Session.
Use an <asp:Repeater> to display the items by data-binding it to your list.
In the repeater's ItemTemplate, you can write out your <asp:Panel> that can contain a <asp:DropDownList>. Use the ItemCommand property of the drop-down list to bind it to a server-side event handler. Similarly you can put an <asp:Button> in the template and bind the ItemCommand property of this to another server-side event handler.
When you click Add, you'll postback to the server, add to your list, save it in session, re-bind the repeater.
When you click a Remove, you'll postback to the server, remove the item from your list, save it in session, re-bind the repeater.
This way lets ASP.Net handle all the control creation for you. However, if you really want to do all that yourself, then this Infinities Loop blog post is required reading.
I don't think this will work. If you create the dropdownlists in the PageLoad event, the viewstate will never get bound to it, and you will never see the option selected by the user.
You should create the controls OnInit, then when the PostBack occurs the ViewState data will get bound to the control and you will be able to access it.