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Multiple link button on same cell of gridview - click event is not firing - c#

I have created multiple linkbutton on same cell of gridview row. But it's click event is not firing. On click event, I have to get StudentID defined in RowDataBound of Gridview.
protected void gvStudent_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
//loop through the cell.
for (int j = 1; j < e.Row.Cells.Count; j++)
{
string[] arrLinks = null;
if (!string.IsNullOrEmpty(e.Row.Cells[j].Text.ToString()) && e.Row.Cells[j].Text.ToString() != " ")
{
arrLinks = e.Row.Cells[j].Text.Split(',');//Rahul-3495,Meera-2323
}
if (arrLinks != null)
{
for (int i = 0; i < arrLinks.Length; i++)
{
LinkButton btnLink = new LinkButton();
string StudentName= (arrLinks[i].Split('-').First()).ToString();//Rahul
string StudentID = (arrLinks[i].Split('-').Last()).ToString();//3495
btnLink.ID ="btn_" + StudentID;
btnLink.Text = StudentName + "<br>";
// btnLink.Click += new EventHandler(StudentButtonsclick);
btnLink.CommandName = "btnLink";
e.Row.Cells[j].Controls.Add(btnLink);
}
}
}
}
}
protected void gvStudent_RowCommand(sender s, GridViewCommandEventArgs e)
{
if (e.CommandName == "btnLink")
{ }
}
<asp:GridView ID="gvStudent" runat="server" AutoGenerateColumns="true"
CssClass="gridview_alter"
OnRowDataBound="gvStudent_RowDataBound" OnRowCommand="gvStudent_RowCommand">
</asp:GridView>

Ok, the problem is that controls that require events that are created "after" the page has been rendered cannot really be wired up. You would have to move the code to a earlier event. So you are free to add controls, but they will in "most" cases be rendered TOO LATE to have events attached. Thus when you click on the link button, nothing fires.
So there are two solutions I can think of that will work.
First, set the control to have a a post back URL, and include a parameter on that post back.
eg this:
Dim lnkBtn As New LinkButton
lnkBtn.Text = "<br/>L" & I
lnkBtn.ID = "cL" & I
lnkBtn.PostBackUrl = "~/GridTest.aspx?r=" & bv.RowIndex
If you put a PostbackUrl, then when you click on the button, the page will post back. However, the grid row events such as rowindex change, or row click event etc. will NOT fire. So, if you willing to have a parameter passed back to the same page as per above, then you can pass the 1-3 (or 1-N) values you have for each control.
Of course that means you now have a parameter on the web page URL (and users will see this). You of course simply pick up the parameter value on page load with the standard
Request.QueryString["ID"] or whatever.
However, another way - which I think is better is to simple wire up a OnClickClick() event in js, and thus do this:
I = 1 to N
Dim lnkBtn As New LinkButton
lnkBtn.Text = "<br/>L" & I
lnkBtn.ID = "cL" & I
lnkBtn.OnClientClick = "mycellclick(" & I & ");return false;"
Now in above note how I am passing "I" to the js routine. You would pass your 200, 300 or whatever value you want.
then you script will look like this:
<script>
function mycellclick(e) {
__doPostBack("MySelect", e);
}
</script>
So above simply takes the value passed from the cell click (and linkbutn), and then does the postback with a dopostback. I used "MySelect", and you can give that any name you want.
Now, in the on-load event, you can simply go like this:
If Request("__EVENTTARGET") = "MySelect" Then
Dim mypassvalue As String = Request("__EVENTARGUMENT").ToString
Debug.Print("row sel for MySelect = " & mypassvalue)
End If
So, you are 100% correct - clicking on those controls does NOT fire server side event, and they are wired up too late for this to occur. so you can and often do say add some columns or controls to a gridview, but they are created and rendered TOO LATE for the events to be wired up (and thus they don't fire when clicked on).
But, you can add a postback to the lnkbutton, and you can also add a OnClickClick() event (JavaScript function call) and they will both work. I don't like parameters in the URL appearing when you click, so I think the js script call as per above works rather nice.
So while in the comments I noted (and suggested) that you have to set the CommandName="Select". This suggesting still holds true (without CommandName = select, then the rowindex will not fire. You can't use just ANY name - it MUST be select. However this ONLY works if the control is part of the grid and not added on the fly. As noted, it might be possible to move the grid event to "earlier" event (page initialize) but it going to be a challenge and will require you to re-organize the page. The most clean, and one that does not require parameters in the URL is adding that js OnClientClick() event. You can however set the controls postbackurl and along with a parameter in the URL, and that also can work well if you open to URL with parameters (I don't like them).

I would recommend using CommandName and OnRowCommand event for GridView. Here is how you should do it:
protected void gvStudent_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
//loop through the cell.
for (int j = 1; j < e.Row.Cells.Count; j++)
{
string[] arrLinks = null;
if (!string.IsNullOrEmpty(e.Row.Cells[j].Text.ToString()) && e.Row.Cells[j].Text.ToString() != " ")
{
arrLinks = e.Row.Cells[j].Text.Split(',');//Rahul-3495,Meera-2323
}
if (arrLinks != null)
{
for (int i = 0; i < arrLinks.Length; i++)
{
LinkButton btnLink = new LinkButton();
string StudentName= (arrLinks[i].Split('-').First()).ToString();//Rahul
string StudentID = (arrLinks[i].Split('-').Last()).ToString();//3495
btnLink.ID = "btn_" + StudentID; // Good to concatenate a string instead just a number in the ID.
btnLink.Text = StudentName + "<br>";
btnLink.CommandName = "btnLink"; // Add a CommandName
e.Row.Cells[j].Controls.Add(btnLink);
}
}
}
}
}
protected void GridView1_RowCommand(sender s, GridViewCommandEventArgs e)
{
if (e.CommandName == "btnLink")
{
// Link Button was clicked.
var linkButton = (LinkButton)sender;
if (linkButton != null)
{
var studentId = linkButton.ID.Replace("btn_", ""); // Remove the concatenated string from the id.
// Do stuff with the student id.
// I would highly not recommend getting the id from a button element, as it could be modified using browser inspect elements. Instead use, GridView DataKeys.
}
}
}
You should add RowCommand event in your GridView as well to get it going. e.g:
<asp:GridView runat="server" ID="GridView1" OnRowCommand="GridView1_RowCommand">
<!-- Rest of the elements -->
</asp:GridView>

Command event not firing asp.net for dynamically created control

I've got the following code that creates an image button dynamically on a li html tag. When I click the image button it does not fire the event. What am I doing wrong please?
Code that generates the control:
ImageButton cmdEdit = new ImageButton();
cmdEdit.ImageUrl = "~/Images/phone_book_edit.png";
cmdEdit.ID = "cmdEdit" + recordcount.ToString();
cmdEdit.Attributes["class"] = "liQuestionsLabel2";
cmdEdit.Width = 30;
cmdEdit.CommandName = "Edit";
cmdEdit.CommandArgument = (recordcount - 1).ToString();
cmdEdit.Command += new CommandEventHandler(EditQuestion_Command);
li.Controls.Add(cmdEdit);
Event code:
protected void EditQuestion_Command(object sender, CommandEventArgs e)
{
Response.Write("here");
}

Dynamically generated controls lose their state after they are rendered. For you to access them again once you postback, you will have to recreate them in the code-behind along with recreating the attached events as well.
Put the above code in your Page_Load but not inside the if(!IsPostback) so that it gets recreated and you can then access its event.
Other than that, the above code works fine for me when I recreated the same control in my page.

Postback from Dynamic Content

I am dynamically building some HTML content on a WebForms page, using HtmlGenericControl().
HtmlGenericControl p = new HtmlGenericControl("p");
// ...
ListItems.Controls.Add(p);
But now I need to add a button to the paragraph created above, and the button needs to do a postback when clicked.
Must I completely rework this code to load child controls, which can contain real server-side buttons? Or is there a way to inject buttons capable of some type of postback?

Here's a test method and test EventHandler that, if called, will add a button control with a server-side Click event to ListItems. The commented-out code will change the markup of the ListItems object if InnerHtml is available but I rethought that approach and assumed the existence of a textbox on the page that would show the results of the click event firing. There are a number of concerns that you'll want to handle if you need those child controls to be present from one postback to another, though- for instance, if Test() isn't called every time the page loads that button won't be created and there will be no way to call its EventHandler unless other controls also call it.
public void Test()
{
System.Web.UI.HtmlControls.HtmlGenericControl p = new System.Web.UI.HtmlControls.HtmlGenericControl("p");
p.InnerHtml = #"<strong>Test</strong>";
// ...
ListItems.Controls.Add(p);
Button b = new Button();
b.ID = "cmdTest";
b.Text = "Test";
b.Click += new EventHandler(test_Click);
p.Controls.Add(b);
}
protected void test_Click(object sender, EventArgs e)
{
// ListItems.InnerHtml = "Test button clicked";
txtTestResults.Text = "Test button clicked at " + DateTime.Now.ToShortTimeString();
}

Adding Triggers dynamically on UpdatePanel for dynamially added controls

I am Adding array Buttons to a simple panel dynamically which is located in an Update Panel, now I want to Add triggers for UpdatePanel on click event of these buttons. My codes is as below:
protected void AddButtons()
{
Button[] btn = new Button[a];
for (int q = 0; q < a; q++)
{
btn[q] = new Button();
buttonsPanel.Controls.Add(btn[q]);
btn[q].ID = "QID" + q;
btn[q].Click += new EventHandler(_Default_Click);
btn[q].Attributes.Add("OnClick", "Click(this)");
AsyncPostBackTrigger trigger = new AsyncPostBackTrigger();
trigger.ControlID = btn[q].ID;
trigger.EventName = "Click";
UpdatePanel2.Triggers.Add(trigger);
}
}
Now click event is not fired when i click on any of these bottons and buttons are getting removed.
Please note that these buttons are not available on Page_Init() method.

You need to assign UniqueID instead of ID to AsyncPostBackTrigger.ControlID property. Try to use the following code:
AsyncPostBackTrigger trigger = new AsyncPostBackTrigger();
trigger.ControlID = btn[q].UniqueID;
trigger.EventName = "Click";
UpdatePanel2.Triggers.Add(trigger);

I came across this post when I was attempting to dynamically add triggers to an update panel which contained a gridview. I have buttons in the gridview and defining the trigger in the page doesn't work as a unique ID for each button is generated when each row is created.
Generating the trigger like such;
AsyncPostBackTrigger trigger = new AsyncPostBackTrigger();
trigger.ControlID = btn[q].UniqueID;
trigger.EventName = "Click";
UpdatePanel2.Triggers.Add(trigger);
did not work for me. The control could not be found, however when using the RegisterPostbackControl or the RegisterAysncPostbackControl commands it worked.
The end example is as follows;
protected void BankAccountDocumentGridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
LinkButton linkButton = (LinkButton)e.Row.Cells[3].FindControl("DocumentsDownloadButton");
ScriptManager.GetCurrent(Page).RegisterPostBackControl(linkButton);
}
}
I figured that the original poster or others who come across this post may benefit from my findings.

Dynamically created content is updating "a step behind" on button click

So I am creating a simple question/answer format and having an issue when submitting an answer. I dynamically create divs/buttons/textboxs from the database via a "RenderQuestions()" function. This creates a list of questions and answer textbox/buttons. When attempting to answer a question, I type my answer click submit and nothing happens. I do it again and it shows my first answer. It's a "step behind".. If I refresh it then shows all answers as it should. I've been struggling with this all night. Here's some code:
-----My page load----- (Relevant parts)
protected void Page_Load(object sender, EventArgs e)
{
//If authenticated hide login & show welcome bloc
if (User.Identity.IsAuthenticated)
{
//Show question & render
questionsBloc.Visible = true;
//if(Page.IsPostBack)
RenderQuestions();
}
-----RenderQuestions() function---- (The relevant parts)
//Initialize & get answers
List<Answer> answers = new List<Answer>();
answers = um.GetAnswers(q.QuestionID);
//Initialize html render
HtmlGenericControl questionDiv = new HtmlGenericControl("div");
TextBox txtAnswer = new TextBox();
Button btnAnswer = new Button();
//Set Answer Button
btnAnswer.Text = "Answer";
btnAnswer.Click += new EventHandler(btnAnswer_Click);
//Set ID's
btnAnswer.ID = "btnAnswer" + q.QuestionID.ToString();
questionDiv.ID = "questionDiv" + q.QuestionID.ToString();
//Set classes
questionDiv.Attributes.Add("class", "questionBloc");
btnAnswer.CausesValidation = false;
btnAnswer.EnableViewState = false;
//btnAnswer.UseSubmitBehavior = true;
//Fill inner text with question
questionDiv.InnerText = q.QuestionContent; //Insert question..
//actionDiv.InnerText = "Like/Dislike/Comment/Flag"; //Insert answer..
//Add answer textbox and button to action div
actionDiv.Controls.Add(btnAnswer);
//Add question div to qaDiv
qaDiv.Controls.Add(questionDiv);
//Add action div to qaDiv
qaDiv.Controls.Add(actionDiv);
//Add all controls to feedbloc
feedBloc.Controls.Add(qaDiv);
-----My btnAnswer event handler -----
private void btnAnswer_Click(object sender, EventArgs e)
{
UserManager um = new UserManager();
um.PostAnswer("My first answer!");
//RenderGlobalFeed();
}
That's every reference to my button.. Should I be initializing the btn click event in my page_init? Any help is much appreciated.
Thanks guys

Set AutoPostBack=true on btnAnswer. It's not triggering the server to act on the button click.

If you want to get event btnAnswer_Click triggered , then you must render the same Content and assign the eventHandler in every pageload(ie; the page load after the client button click must render the button again and EventHandler must be assigned).
Asp.net won't trigger the event if it doesn't find the controls in the pageload. Remember, after clicking a button, the page load event triggers first and then only the Click_event will be triggered.
The RenderQuestions() must be called in the btnAnswer_Click Event too. This will avoid the a step back problem.
In this scenario I would recommend you to learn about ajax (using jQuery library) requests in asp.net (using WebMethods or webservices) to avoid these postbacks.