I have an ASP.NET webform that has a Listbox that I'm adding items to dynamically using a Button (using Session to save the list between postbacks). When an Item is added to the Listbox I want to add an ImageButton that I can click to change the color of the newly created button. I know I should be doing something differently, like adding the controls in Page_Init but then the Add Button event (cmdAdd_Click) hasn't gone off yet. I can't seem to figure out how to do it in a clean and simple way.
.aspx snippet:
<asp:Button ID="cmdAdd" runat="server" OnClick="cmdAdd_Click" />
<asp:ListBox ID="lboObjects" runat="server"></asp:ListBox>
<asp:Panel ID="pnlButtons" runat="server"></asp:Panel>
.cs code Behind Snippet:
protected void cmdAdd_Click(object sender, ImageClickEventArgs e)
{
// Simplified for Brevity
((List<Line>)Session["lstObjects"]).Add("Unique Object"); // the object will be unique.
lboObjects.DataSource = ((List<Line>)Session["lstObjects"]);
lboObjects.DataBind();
// Clear out b/c I intend on having a cmdRemove_Click, but not showing for simplicity
pnlButtons.Controls.Clear();
foreach (object obj in ((List<Line>)Session["lstObjects"]))
{
ImageButton imageButton = new ImageButton();
imageButton.ID = obj.ToString();
imageButton.Click += cmdChangeColor_Click;
pnlButtons.Controls.Add(imageButton);
}
}
protected void cmdChangeColor_Click(object sender, ImageClickEventArgs e)
{........}
You want to load controls inside Page_Init. Otherwise, they are not in control tree, and they won't be able to trigger cmdChangeColor_Click event.
For example,
protected void Page_Init(object sender, EventArgs e)
{
var list = Session["lstObjects"] as List<Line>;
if (list != null)
{
foreach (var obj in list)
{
ImageButton imageButton = new ImageButton {ID = obj.ToString()};
imageButton.Click += cmdChangeColor_Click;
pnlButtons.Controls.Add(imageButton);
}
}
}
Related
I have an .aspx page and I want to dynamically add textboxes to the page on the click of a button. For this purpose I've added a placeholder on the page and add the controls to the server side when the button is clicked.
<asp:PlaceHolder runat="server" ID="NotificationArea"></asp:PlaceHolder>
<asp:Button ID="AddNotification" runat="server" Text="Add" OnClick="AddNotification_Click" />
<asp:Button ID="RemoveNotification" runat="server" Text="Remove" OnClick="RemoveNotification_Click" />
I store the textboxes in a session variable so that I can continue adding and removing textboxes indefinitely. Below I put the on_click methods for the add and remove buttons:
protected void AddNotification_Click(object sender, EventArgs e)
{
List<TextBox> notifications = (List<TextBox>)(Session["Notifications"]);
notifications.Add(new TextBox());
notifications[notifications.Count - 1].Width = 450;
notifications[notifications.Count - 1].ID = "txtNotification" + notifications.Count;
foreach (TextBox textBox in notifications)
{
NotificationArea.Controls.Add(textBox);
}
NotificationArea.Controls.Add(notifications[notifications.Count - 1]);
Session["Notifications"] = notifications;
}
protected void RemoveNotification_Click(object sender, EventArgs e)
{
List<TextBox> notifications = (List<TextBox>)(Session["Notifications"]);
if (notifications.Count > 0)
{
NotificationArea.Controls.Remove(notifications[notifications.Count - 1]);
notifications.RemoveAt(notifications.Count - 1);
}
foreach (TextBox textBox in notifications)
{
NotificationArea.Controls.Add(textBox);
}
Session["Notifications"] = notifications;
}
This works nicely. It continually adds new textboxes and removes the last one if the remove button is clicked. Then, when I tried to get the text from the textboxes I ran into a problem. I never actually store the text that are typed into the textboces in the session variable. Just the empty textboxes that are initially created. Also, see below:
int count = NotificationArea.Controls.Count;
Debugging this shows that the count of the controls in the NotificationArea is 0. How do I access the text for these dynamically added textbox controls? Do I somehow add an ontext_change event to the textboxes that saves the particular textbox's Text into its equivalent in the session variable? How do I go about doing that?
Found the solution here. Turns out you need to re-create all controls that were added dynamically on each post back
public void Page_Init(object sender, EventArgs e)
{
CreateDynamicControls();
}
private void CreateDynamicControls()
{
notifications = (List<TextBox>)(Session["Notifications"]);
if (notifications != null)
{
foreach (TextBox textBox in notifications)
{
NotificationArea.Controls.Add(textBox);
}
}
}
Doing this allows me to access the content of these controls at any time.
I am working on a page that accepts scanned input into a textbox. Once input is entered into the textbox, a user control that contains additional fields for the input item is dynamically generated via autopostback. The user control also contains a link button that is intended to delete the item (itself). Clicking this button generates a "delete" event that is supposed to bubble up to the parent.
Unfortunately this does not seem to happen - the deletion handling code is never reached. My understanding is that it is because the controls have not been generated yet at page load, so the event handlers have not been created yet. But since I don't know what controls need to be generated at page load (since the user input hasn't been processed yet), I can't move the code to generate the user controls to PageLoad.
How should this be handled? Am I going about this the wrong way? Most of my relevant code is below.
Thanks for any help!
page.aspx:
Enter SKU (tab to enter):
<asp:TextBox ID="EntryTextBox" CssClass="textbox" AutoPostBack="true" OnTextChanged="newItem" runat="server"></asp:TextBox>
<asp:Panel ID="itempanel" runat="server">
</asp:Panel>
page.aspx.cs:
protected void newItem(object sender, EventArgs e)
{
// we need to store item entries in ViewState so they comeback on postback;
// they can't be stored in the controls themselves as the controls will
// disappear
ViewState["skus"] += "\t" + EntryTextBox.Text;
ViewState["descs"] += "\t" + itemLookup(EntryTextBox.Text);
// ...more item descriptors...
updateItemPanel();
}
protected void updateItemPanel()
{
// generate a control for each item entered in ViewState
itempanel.Controls.Clear();
List<string> skus = new List<string>(ViewState["items"].ToString().Substring(1).Split('\t'));
List<string> descs = new List<string>(ViewState["descs"].ToString().Substring(1).Split('\t'));
// ...more item descriptors...
int i = 0;
foreach (string sku in skus)
{
item newitemctrl = (item)Page.LoadControl("~/item.ascx");
newitemctrl.line = (i + 1).ToString();
newitemctrl.sku = skus[i];
newitemctrl.description = descs[i];
// ...more item descriptors...
newitemctrl.deleteLinkClicked += new EventHandler(deleteClicked);
itempanel.Controls.Add(newitemctrl);
i++;
}
}
protected void deleteClicked(object sender, EventArgs e)
{
List<string> skus = new List<string>(ViewState["skus"].ToString().Substring(1).Split('\t'));
List<string> descs = new List<string>(ViewState["descs"].ToString().Substring(1).Split('\t'));
// ...more item descriptors...
item olditemctrl = (item)sender;
skus.RemoveAt(Convert.ToInt32(olditemctrl.number) - 1);
descs.RemoveAt(Convert.ToInt32(olditemctrl.number) - 1);
ViewState["skus"] = skus.ToString();
ViewState["descs"] = descs.ToString();
updateItemPanel();
}
item.ascx:
<asp:LinkButton ID="DeleteLinkButton" runat="server" onclick="DeleteLinkButton_Click">Delete</asp:LinkButton>
item.ascx.cs:
public event EventHandler deleteLinkClicked;
protected void DeleteLinkButton_Click(object sender, EventArgs e)
{
if (this.deleteLinkClicked != null)
{
this.deleteLinkClicked(new object(), new EventArgs());
}
}
You can dispatch a postback event in javascript by adding this as onclick event:
__doPostBack("<%= button.ClientID %>", "");
DoPostBack has two arguments, the first is the ID, the second is the event name.
I used this solution successfully.
You'll find more information here.
Note:
This itself does not fire the event automatically, but you can see what you want to happen in the Load Event of your page.
You can get the arguments like this: : Request.Form["__EVENTTARGET"]
You have full access to the form data, so you can also get the values from the dynamically created controls
I have a drop down which has the list of delegates. When the user selects a delegate then I populate the available meet-timings in the second dropdown using the selectedindexchange event of the 1st dropdown
Aspx page
<asp:DropDownList ID="delegate_ddl" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddldelegates_SelectedIndexChanged" Width="200px"></asp:DropDownList>
<asp:DropDownList ID="delegatetime_ddl" runat="server" Width="90px"></asp:DropDownList>
<asp:Button ID="adddelegate" runat="server" Text="Add" onclick="adddelegate_Click"/>
.cs page
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
DataSet ds1 = getdata.getdelegatelist();
delegate_ddl.DataSource = ds1.Tables[0];
delegate_ddl.DataTextField = "DELEGATE_NAME";
delegate_ddl.DataValueField = "DELEGATE_ID";
delegate_ddl.DataBind();
delegate_ddl.Items.Insert(0, "--Select--");
}
}
protected void ddldelegates_SelectedIndexChanged(object sender, EventArgs e)
{
string delselection = delegate_ddl.SelectedValue.ToString();
DataSet ds2 = getdata.getdelegatetimelist(delselection);
if (ds2.Tables[0].Rows.Count > 0)
{
delegatetime_ddl.DataSource = ds2.Tables[0];
delegatetime_ddl.DataTextField = "TIMESLOT";
delegatetime_ddl.DataValueField = "TIMEID";
delegatetime_ddl.DataBind();
}
else
{
time_lbl.Text = "No slots Open";
}
}
protected void adddelegate_Click(object sender, EventArgs e)
{
string delegateselected = delegate_ddl.SelectedValue.ToString();
string timeslotselected = delegatetime_ddl.SelectedValue.ToString();
getdata.delegatemeetinsert(personidd, delegateselected, timeslotselected);
}
Now the data gets inserted – but my question here is
As soon as the user click add button I would like to display the delegate selected and the time slot selected in a some sort of a grid view or dynamic table below with a delete option.
Can someone please provide a code sample in C# to achieve the above
Instead of using Gridview for displaying data use some basic control like Labels,it will reduce lot's of unncessary code. use Asp.net 'Panel' control and encapsulate all label and button(for delete purpose) into Panel then hide/show according to need. here is the outline of code that might help you,
if(!page.IsPostBack) // This goes into Page_Load
{
Panel1.Visible=false;
}
protected void adddelegate_Click(object sender, EventArgs e) // add this additional code
{
Panel.Visible=True;
GetDelegate()// This method retrieve the delegate you inserted..
Lable1.Text= "Set here Delegate name you just Retrieved"
Label2.Text="Delegate time you retrived"
}
protected void BtnRemovedelegate_Click(object sender, EventArgs e)
{
string Personidd= retrieve person id
string delegateName= Lable1.text;
String timeslot=Label2.Text
SomeDeleteMethod(personidd, delegateName, timeslot);
Panel1.Visible=false;
}
Hope you get the idea..
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.