c# - How to add runat=server attribute to html buttons -

i have multiple html buttons generated server side method on csharp class.
result is:

<button id='btn1' runat='server' onserverclick='btn_click'>apply</button> <button id='btn2' runat='server' onserverclick='btn_click'>apply</button> <button id='btn3' runat='server' onserverclick='btn_click'>apply</button> ... <button id='btnn' runat='server' onserverclick='btn_click'>apply</button> 

i add btn_click event behind code:

protected void btn_click (object sender, eventargs e) {     string id = (sender control).clientid;     msg = id; } 

as can see want buttonid when click on of buttons, btn_click won't call , can't buttonid.
i using asp.net website c#4.0.

the problem need generate buttons using server side , runat attribute doesn't work method . how can fix problem?
method body generated buttons

for (int = 0; < dt.rows.count; i++)         {             datetime dttemp = datetime.parse(dt.rows[i]["messagedate"].tostring());             if (dt.rows[i]["isread"].tostring() == "true")                 readed = "messagereaded";             else                 readed = "messagenew";             post += "<div class='modal fade' id='mymodal" + dt.rows[i]["messageid"].tostring() + "' tabindex='-1' role='dialog' aria-labelledby='mymodallabel'>"                 + "<div class='modal-dialog' role='document'>"                 + "<div class='modal-content'>"                 + "<div class='modal-header'><button type='button' class='close' data-dismiss='modal' aria-label='close'><span aria-hidden='true'>&times;</span></button><h4 class='modal-title' id='mymodallabel'><span style='font-weight:bold'>subject</span> : " + dt.rows[i]["subject"].tostring() + "</h4></div>"                 + "<div class='modal-header'><p><span style='font-weight:bold'>date</span> : " + dttemp.tostring("yyyy/mm/dd") + "</p>"                 + "<p><span style='font-weight:bold'>time</span> : " + dt.rows[i]["messagetime"].tostring() + "</p>"                 + "<p><span style='font-weight:bold'>email</span> : " + dt.rows[i]["email"].tostring() + "</p></div>"                 + "<div class='modal-body'>" + dt.rows[i]["message"].tostring() + "</div>"                 + "<div class='modal-footer'><button type='button' class='btn btn-default' data-dismiss='modal'>close</button>"                 + "<button id='btn" + dt.rows[i]["messageid"].tostring() + "'  class='btn btn-danger' onclick='deletemessage_click'>delete</button></div>"                 + "</div></div></div>";             string narrow = special.timetonarrow(dt.rows[i]["messagedate"].tostring(), dt.rows[i]["messagetime"].tostring());             post += "<a data-toggle='modal' data-target='#mymodal" + dt.rows[i]["messageid"].tostring() + "' href='#' class='list-group-item " + readed + "'><span class='badge'>" + narrow + "</span><i class='fa fa-fw fa-comment'></i> <span>"                      + dt.rows[i]["name"].tostring() + "</span> : <span>" + dt.rows[i]["subject"].tostring() + "</span></a>";         } 

so problem on
<button id='btn" + dt.rows[i]["messageid"].tostring() + "' runat='server' class='btn btn-danger' onserverclick='deletemessage_click'>delete</button>

edit post : can see can't use asp:button because using bootstrap modal. if think can still use asp:button please write code , show me how .thanks

as other's have said, problem asp.net won't recognise runat="server" when generate controls string of html.

your code should done in different way, if wanted change have done work little differently.

instead of runat="server" on buttons, make them submit buttons , assign them name , value, example...

instead of this:

<button id='btn1' runat='server' onserverclick='btn_click'>apply</button> <button id='btn2' runat='server' onserverclick='btn_click'>apply</button> <button id='btn3' runat='server' onserverclick='btn_click'>apply</button> 

do (note have same name):

<button name="btn" type="submit" value="1">apply</button> <button name="btn" type="submit" value="2">apply</button> <button name="btn" type="submit" value="3">apply</button> 

then in page_load event can detect if 1 of these buttons clicked following:

if (page.ispostback) {     if (request.form["btn"] != null)     {          //a btn clicked, it's value          int btn = int.parse(request.form["btn"]);           //do btn number     } } 

here's little sample has 3 buttons , displays number of button clicked:

test.aspx

<%@ page language="c#" autoeventwireup="true" codebehind="test.aspx.cs" inherits="test" %> <!doctype html> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server">     <title></title> </head> <body>     <form id="form1" runat="server">         <button name="btn" type="submit" value="1">apply</button>         <button name="btn" type="submit" value="2">apply</button>         <button name="btn" type="submit" value="3">apply</button>     </form> </body> </html> 

test.aspx.cs

using system; using system.collections.generic; using system.linq; using system.web; using system.web.ui; using system.web.ui.webcontrols;  public partial class test : system.web.ui.page {     protected void page_load(object sender, eventargs e)     {         if (page.ispostback)         {             if (request.form["btn"] != null)             {                 int btn = int.parse(request.form["btn"]);                  response.write(btn);             }         }     } }