Develop Reference

CheckBox CheckedChanged event added from code behind

I have a couple of checkboxes that I add from my code behind, but I can't get the CheckedChanged event to fire.
This code is being called on page load:
CheckBox cb = new CheckBox();
cb.AutoPostBack = true;
cb.CheckedChanged += cb_CheckedChanged;
cb.ToolTip = dr["Id"].ToString();
cb.ID = Guid.NewGuid().ToString();
Label lbl = new Label();
lbl.Text = dr["Id"].ToString();
lbl.AssociatedControlID = cb.ID;
dvCheckboxes.Controls.Add(cb);
dvCheckboxes.Controls.Add(lbl);
dvCheckboxes.Controls.Add(new LiteralControl("<br />"));
And the event:
void cb_CheckedChanged(object sender, EventArgs e)
{
System.Diagnostics.Debug.Write(((CheckBox)sender).ToolTip);
}
I've put a breakpoint in the CheckedChanged event, but it's never reached.
What I've tried:
putting the code in if(!IsPostBack), but no difference.
cb.CheckedChanged += new EventHandler(cb_CheckedChanged);
cb.CheckedChanged += new EventHandler(this.cb_CheckedChanged);
cb.ViewStateMode = System.Web.UI.ViewStateMode.Enabled;
tried putting the code in Page_Init instead of Page_Load

#johan, Try this. Create the checkboxes in PageInit instead of Pageload. Also provide an appropriate id for the Checkbox.
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Page_init(object sender, EventArgs e)
{
CheckBox cb = new CheckBox();
cb.AutoPostBack = true;
cb.CheckedChanged +=cb_CheckedChanged;
cb.CausesValidation = false;
cb.ToolTip = "Hello";
cb.ID = "chk_test";
Label lbl = new Label();
lbl.Text = "test";
lbl.AssociatedControlID = cb.ID;
dvCheckboxes.Controls.Add(cb);
dvCheckboxes.Controls.Add(lbl);
dvCheckboxes.Controls.Add(new LiteralControl("<br />"));
}
protected void cb_CheckedChanged(object sender, EventArgs e)
{
System.Diagnostics.Debug.Write(((CheckBox)sender).ToolTip);
}

Add event in your site code - not code behind:
<asp:CheckBox ID="cb" Runat="server" CheckedChanged="cb_CheckedChanged" />
Hope this helps.

dynamic linkbutton not calling command when clicked

New to dynamic controls, but until now I have been creating them successfully in a
template field in my gridview, recently switched from a hyperlink to a link button
and had to make some changes but still not working
In my page I have the following code (abridged to salient parts)
protected void Page_Load(object sender, EventArgs e)
{
if (!this.IsPostBack)
{
...
...
TemplateField tf = new TemplateField();
tf.HeaderText = "Action";
tf.ItemTemplate = new AssignPage.MyTemplate(..., mylb);
GridView1.Columns.Add(tf);
protected void Page_PreInit(object sender, EventArgs e)
{
LinkButton lb = new LinkButton();
lb.Text = "AssignAll";
lb.Command += new CommandEventHandler(AssignAll_Click);
lb.CommandName = "XXX";
this.mylb = lb;
protected void AssignAll_Click(object sender, CommandEventArgs e)
{
string[] arg = new string[2]; // BREAK POINT HERE
arg = e.CommandArgument.ToString().Split(';');
...
...
Response.Redirect("BaseAndRepeats.aspx?id=" + r.Event.ID);
In the template class I have I have
LinkButton lb;
public MyTemplate(..., LinkButton _lb)
{
...
lb = _lb;
...
public void InstantiateIn(System.Web.UI.Control container)
{
...
...
// various conditional statements
lb.CommandArgument = mylist[rowCount].ReqtID.ToString() + ";" + mylist[rowCount].RotaUser;
container.Controls.Add(lb);
...
The break point in the handler is never reached
I thought I was creating the linkbutton in the right place
the linkbutton appears in the grid quite happily
when I click on the linkbutton there is a call
to Page_PreInit and to Page_Load and as I expected
it is a postback.
But AssignAll_Click is never called.
In the browser footer it shows "javascript: __dooPsotabck(..." when you hover
over the buttonlink

I believe the problem is this line:
lb.Command += new CommandEventHandler(AssignAll_Click);
Change it to:
lb.Command += AssignAll_Click;
Edit:
Also you want to move it from Page_PreInit to Page_Init but you may find more success with it in Page_Load (outside the IsPostBack). Here's an example that works for me:
On the ASPX page:
<asp:Panel ID="TestPanel" runat="server" />
Codebehind:
protected void Page_Init(object sender, EventArgs e)
{
//Init used because TestPanel doesn't exist yet
CreateTestButton();
}
private void CreateTestButton()
{
var lb = new LinkButton();
lb.Text = "hello";
lb.Command += lb_Command;
TestPanel.Controls.Add(lb);
}
void lb_Command(object sender, CommandEventArgs e)
{
throw new NotImplementedException();
}
Going over your code it looks like your adding another column into your GridView and creating a button inside that column for each row - but you've got the column being added on Page_Load and the button being created and bound to it before in Page_PreInit

Generic event handler not firing from dynamic buttons

I have a bunch of buttons being dynamically created and setting its click event to an event handler...When I run it they handler in never firing, I've stepped through the code and nothing seems out of the ordinary but it just won't fire.
Here is a snippet of the code where the button is being created..
for (cellCtr = 1; cellCtr <= 9; cellCtr++)
{
Button button = new Button();
HyperLink link = new HyperLink();
TableCell tCell = new TableCell();
if (rowCtr == rN)
break;
string myStr = daccess.dsSubjects.Tables[0].Rows[rowCtr]["SubjectName"].ToString();
int myID = Convert.ToInt32(daccess.dsSubjects.Tables[0].Rows[rowCtr]["SubjectID"].ToString());
button.ID = Convert.ToString(myID);
button.Text = myStr;
button.CssClass = "btn btn-primary btn-sm";
button.Click += ButtonSubjectClick;
tCell.Controls.Add(button);
tRow.Cells.Add(tCell);
rowCtr++;
if (cellCtr == rN)
{
rowCtr = rowCtr - 1;
break;
}
}
and here is the handler that's it suppose to call...
void ButtonSubjectClick(object sender, EventArgs e)
{
Button button = (Button)sender;
daccess.DeleteSubjects(Int32.Parse(button.ID.ToString()));
button.CssClass = "btn-active";
}
When its ran, the source looks like this
<input type="submit" name="38" value="Math" id="38" class="btn btn-primary btn-sm" />

This code works for me:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
// do something if needed
}
// outside of postback, you need to add it each time
Button button = new Button();
button.ID = "btn1";
button.Text = "clicky me";
button.Click += new EventHandler(ButtonSubjectClick);
pnl.Controls.Add(button);
}
void ButtonSubjectClick(object sender, EventArgs e)
{
Button button = (Button)sender;
button.Text = "clicked me";
}
I believe it's a question about how are you adding your button to the page. I'm adding my button at each postback and it is thus registered by the server.
If you are adding your buttons in another event then you could use viewstate or session variables, store some kind of a flag to create the button and then check for this flag in each postback.
Edit, for the sake of clarity, pnl is a Panel on my page:
<form id="form1" runat="server">
<div>
<asp:Panel ID="pnl" runat="server"></asp:Panel>
</div>
</form>

Dynamic Control’s Event Handler’s Working

I have following code that adds dynamic LinkButton on the click event of a normal button. The LinkButtons need a EventHandler “LinkButton_Click“. Since the event handler need to be registered while Page_Load/Page_Init itself, I am first adding all the possible links within Page_Load (in postback scenario). (There are totally fours linkbuttons; only two will be displayed in the screen based on business scenario)
The code is working fine and the event handlers are getting invoked on click event.
Note: The business scenario is – if the current time’s second portion is less than 30, the first two LinkButtons need to be displayed; if greater than 30 the last two LinkButtons need to be displayed.
Note: The controls are cleared and added again inside PopulateLinksBasedOnCriteria() method
QUESTIONS
In the PopulateLinksBasedOnCriteria() method, I am newly creating the link button instances. Still the event handler is firing. This is working because the ID that got added in the Page_Load is same. Is there any MSDN reference that substantiate this behavior? (I.e. the event handler will be based on the IDs registered while Page_Load/Page_Init. This will work even if the controls are cleared and added again)
There is duplicate code in creating LinkButtons – one inside Page_Load and other inside PopulateLinksBasedOnCriteria() method. Is there a better way to achieve this business task without duplicate code?
MarkUp
<form id="form1" runat="server">
<div>
<asp:Button ID="btnAdd" runat="server" Text="Add" OnClick="btnAdd_Click" />
<br />
<asp:PlaceHolder ID="plhDynamicLinks" runat="server"></asp:PlaceHolder>
</div>
</form>
CODE BEHIND
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack)
{
LinkButton lnk1 = new LinkButton();
lnk1.ID = "D1";
lnk1.Text = "A";
//Event handler must be registered in the Page_Load/Page_Init
lnk1.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk1);
LinkButton lnk2 = new LinkButton();
lnk2.ID = "D2";
lnk2.Text = "B";
lnk2.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk2);
LinkButton lnk3 = new LinkButton();
lnk3.ID = "D3";
lnk3.Text = "C";
lnk3.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk3);
LinkButton lnk4 = new LinkButton();
lnk4.ID = "D4";
lnk4.Text = "D";
lnk4.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk4);
}
}
protected void LinkButton_Click(object sender, EventArgs e)
{
PopulateLinksBasedOnCriteria();
LinkButton clickedControl = (LinkButton)sender;
Response.Write(DateTime.Now.ToString()+"___"+ clickedControl.ID + " Link Button Clicked" );
}
protected void btnAdd_Click(object sender, EventArgs e)
{
PopulateLinksBasedOnCriteria();
}
private void PopulateLinksBasedOnCriteria()
{
plhDynamicLinks.Controls.Clear();
if (DateTime.Now.Second < 30)
{
LinkButton linkButton1 = new LinkButton();
linkButton1.ID = "D1";
linkButton1.Text = "1";
plhDynamicLinks.Controls.Add(linkButton1);
LinkButton linkButton2 = new LinkButton();
linkButton2.ID = "D2";
linkButton2.Text = "2";
plhDynamicLinks.Controls.Add(linkButton2);
}
else
{
LinkButton linkButton3 = new LinkButton();
linkButton3.ID = "D3";
linkButton3.Text = "3";
plhDynamicLinks.Controls.Add(linkButton3);
LinkButton linkButton4 = new LinkButton();
linkButton4.ID = "D4";
linkButton4.Text = "4";
plhDynamicLinks.Controls.Add(linkButton4);
}
}

I would suggest detecting what causes the PostBack in Page_Load Event On postback, how can I check which control cause postback in Page_Init event and then
if (Page.IsPostBack && *PostBackControl.Name=="btnAdd"*)
{
if (DateTime.Now.Second < 30)
{
LinkButton lnk1 = new LinkButton();
lnk1.ID = "D1";
lnk1.Text = "A";
//Event handler must be registered in the Page_Load/Page_Init
lnk1.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk1);
LinkButton lnk2 = new LinkButton();
lnk2.ID = "D2";
lnk2.Text = "B";
lnk2.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk2);
} else
{
LinkButton lnk3 = new LinkButton();
lnk3.ID = "D3";
lnk3.Text = "C";
lnk3.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk3);
LinkButton lnk4 = new LinkButton();
lnk4.ID = "D4";
lnk4.Text = "D";
lnk4.Click += new EventHandler(LinkButton_Click);
plhDynamicLinks.Controls.Add(lnk4);
}
}
}

How do you add a Gridview programmatically to an UpdatePanel

I can't figure out how to programmatically add a GridView with buttons to an UpdatePanel.
I can do it with simple controls such as buttons and labels, but when I try to add a GridView with buttons a full Postback() occurs.
<%# Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected override void OnInit(EventArgs e)
{
UpdatePanel up1 = new UpdatePanel();
up1.ID = "UpdatePanel1";
Button button1 = new Button();
button1.ID = "Button1";
button1.Text = "Submit";
button1.Click += new EventHandler(Button_Click);
Label label1 = new Label();
label1.ID = "Label1";
label1.Text = "A full page postback occurred.";
GridView gv1 = new GridView();
//Where the xml gets bonded to the data grind
XmlDataSource xds = new XmlDataSource();
xds.Data = xml;
xds.DataBind();
xds.EnableCaching = false;
gv1.DataSource = xds;
createButton(gv1, up1);
gv1.RowCommand += new GridViewCommandEventHandler(CustomersGridView_RowCommand);
gv1.DataBind();
up1.ChildrenAsTriggers = true;
up1.ContentTemplateContainer.Controls.Add(button1);
up1.ContentTemplateContainer.Controls.Add(label1);
up1.ContentTemplateContainer.Controls.Add(gv1);
Page.Form.Controls.Add(up1);
}
protected void Page_Load(object sender, EventArgs e)
{
}
public void CustomersGridView_RowCommand(Object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "buttonClicked")
{
int index = Convert.ToInt32(e.CommandArgument);
}
}
void createButton(GridView g)
{
ButtonField tea = new ButtonField();
tea.ButtonType = ButtonType.Image;
tea.ImageUrl = "~/checkdailyinventory.bmp";
tea.CommandName = "buttonClicked";
tea.HeaderText = "space";
g.Columns.Add(tea);
}
protected void Button_Click(object sender, EventArgs e)
{
((Label)Page.FindControl("Label1")).Text = "Panel refreshed at " +
DateTime.Now.ToString();
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>UpdatePanel Constructor Example</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Button ID="Button2" runat="server" Text="Button" />
<asp:ScriptManager ID="ScriptManager1" runat="server" />
</div>
</form>
</body>
</html>
So how do you add a gridview with buttons programmatically to an UpdatePanel without causing a full PostBack() if the GridView is clicked?
Edit: Other things I have tried
void gv1_RowDataBound(object sender, GridViewRowEventArgs e)
{
AsyncPostBackTrigger t = new AsyncPostBackTrigger();
t.ControlID = e.Row.Cells[0].ClientID;
t.EventName = "blah";
up1.Triggers.Add(t);
}

Well according to:
And I don't mind having the update panel created at the design time. I just need to be able to add stuff (like tables that contain gridviews that contain buttons into it) programmatically and then be able to do a partial postback
Basically I used your code with small changes:
Removed the binding from the Init event and I execute it in the Load event
The UpdatePanel is created at design time with a nested panel, and you simply add your dynamic controls to that panel
This code will do it (it works on my environment):
ASPX
<asp:ScriptManager runat="server" />
<asp:UpdatePanel runat="server">
<ContentTemplate>
<asp:Panel runat="server" ID="myPanel">
</asp:Panel>
<br />
<asp:Label runat="server" ID="lblMessage"></asp:Label>
</ContentTemplate>
</asp:UpdatePanel>
Code behind
protected void Page_Init(object sender, EventArgs e)
{
Button button1 = new Button();
button1.ID = "Button1";
button1.Text = "Submit";
button1.Click += new EventHandler(Button_Click);
Label label1 = new Label();
label1.ID = "Label1";
label1.Text = "A full page postback occurred.";
var s1 = Builder<Product>.CreateListOfSize(15).Build();
GridView gv1 = new GridView();
gv1.DataSource = s1;
createButton(gv1);
gv1.RowCommand += new GridViewCommandEventHandler(CustomersGridView_RowCommand);
this.myPanel.Controls.Add(button1);
this.myPanel.Controls.Add(label1);
this.myPanel.Controls.Add(gv1);
}
void createButton(GridView g)
{
ButtonField tea = new ButtonField();
tea.ButtonType = ButtonType.Image;
tea.ImageUrl = "~/checkdailyinventory.bmp";
tea.CommandName = "buttonClicked";
tea.HeaderText = "space";
g.Columns.Add(tea);
}
protected void Button_Click(object sender, EventArgs e)
{
((Label)Page.FindControl("Label1")).Text = "Panel refreshed at " +
DateTime.Now.ToString();
}
protected void Page_Load(object sender, EventArgs e)
{
this.DataBind();
}
public void CustomersGridView_RowCommand(Object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "buttonClicked")
{
//int index = Convert.ToInt32(e.CommandArgument);
this.lblMessage.Text = DateTime.Now.ToString();
}
}
Output

Couldn't you just put the GridView in there at design time and just hide it by setting Visible=false?
If you don't know how many gridviews you need to repeat then you could wrap the GridView in a ListView. The concept is introduced here:
http://mattberseth.com/blog/2008/01/building_a_grouping_grid_with.html
This might not be the perfect solution I just thought I would offer it seeing as there is a bounty I assume you have hit a brick wall so far.