| Groups | Blog | Home |
asp.net webcontrols : Conditional dynamic loading of a web control?
result of a user action? This can't be done from Page_Load( ), because the Page_Load event fires before the user action can set a property. And yet, if the event handler is added at any time after Page_Load, the button doesn't respond to events. Example: protected void btnUserClicksMe(o,e) { // User has just clicked me, instructing a dynamic button to appear on the page. Button btnDynamic = new Button(); btnDynamic += new System.EventHandler(btnDynamic_Click); this.Controls.Add(btnDynamic); // In a practical application this would be in a table cell or panel. } protected void btnDynamic_Click(o,e) { // This code should run if user clicks on the dynamically created button. // But if event handler is declared at any time after Page_Load, this code never runs, // yet no compiler errors or exceptions are thrown. Response.Write("Hi there!"); } I have been attempting various workarounds to this behavior, but the only methods that have worked have involved client-side code that forces a multiple round trip. Has anyone found a way to make this work?
I am just keeping the example simple. Practical example: The web page has a
textbox that can take filter values, and the contents of the textbox determine how many rows appear in an ASP:TABLE. That table can contain several buttons per row. There is no way to know in advance how many rows are to appear in the table, so the controls in the table can't be created in advance. I know the canned datagrid control handles this sort of scenario, but again, this is just an example. Thanks for taking an interest in my question. Haile [quoted text, click to view] "Leon Friesema" wrote:
> On Mon, 29 Nov 2004 05:05:04 -0800, "haile" > <haile@discussions.microsoft.com> wrote: > > >Anyone know how to load a button and its event handler to a web page as a > >result of a user action? This can't be done from Page_Load( ), because the > >Page_Load event fires before the user action can set a property. And yet, if > >the event handler is added at any time after Page_Load, the button doesn't > >respond to events. Example: > > > >protected void btnUserClicksMe(o,e) > >{ > > // User has just clicked me, instructing a dynamic button to appear on the > >page. > > Button btnDynamic = new Button(); > > btnDynamic += new System.EventHandler(btnDynamic_Click); > > this.Controls.Add(btnDynamic); // In a practical application this would > >be in a table cell or panel. > >} > > > >protected void btnDynamic_Click(o,e) > >{ > > // This code should run if user clicks on the dynamically created button. > > // But if event handler is declared at any time after Page_Load, this code > >never runs, > > // yet no compiler errors or exceptions are thrown. > > Response.Write("Hi there!"); > >} > > > >I have been attempting various workarounds to this behavior, but the only > >methods that have worked have involved client-side code that forces a > >multiple round trip. > > > >Has anyone found a way to make this work? > > > >Haile > > You want to add a button to the page, run-time? Why not add the > button, Visible = false and set the Visible to true when needed? > > Leon.
Leon:
Thanks very much for your reply. You have confirmed my suspicions, because I have been beating myself up on this off and on for the past couple months. I am currently using your method. At the moment I am working on a datagrid with buttons called "Assign," "Lockout," "Edit," and "Refresh" on each row. If I need a postback to the same viewstate, I use buttons. If I need a redirect, I use linkbuttons. So it sounds like we're doing the same thing. Sure would be nice to just make a table in a pinch, though. Or for that matter, any control at all. Let's say I want to load controls on the basis of a state saved in a database (say, for a web form designer application). Datagrids are no help there. If I find a way to do it, I will post it to the group. Though the prospects are dim... Haile [quoted text, click to view] "Leon Friesema" wrote:
> On Mon, 29 Nov 2004 05:31:05 -0800, "haile" > <haile@discussions.microsoft.com> wrote: > > > > >"Leon Friesema" wrote: > > > >> On Mon, 29 Nov 2004 05:05:04 -0800, "haile" > >> <haile@discussions.microsoft.com> wrote: > >> > >> >Anyone know how to load a button and its event handler to a web page as a > >> >result of a user action? This can't be done from Page_Load( ), because the > >> >Page_Load event fires before the user action can set a property. And yet, if > >> >the event handler is added at any time after Page_Load, the button doesn't > >> >respond to events. Example: > >> > > >> >protected void btnUserClicksMe(o,e) > >> >{ > >> > // User has just clicked me, instructing a dynamic button to appear on the > >> >page. > >> > Button btnDynamic = new Button(); > >> > btnDynamic += new System.EventHandler(btnDynamic_Click); > >> > this.Controls.Add(btnDynamic); // In a practical application this would > >> >be in a table cell or panel. > >> >} > >> > > >> >protected void btnDynamic_Click(o,e) > >> >{ > >> > // This code should run if user clicks on the dynamically created button. > >> > // But if event handler is declared at any time after Page_Load, this code > >> >never runs, > >> > // yet no compiler errors or exceptions are thrown. > >> > Response.Write("Hi there!"); > >> >} > >> > > >> >I have been attempting various workarounds to this behavior, but the only > >> >methods that have worked have involved client-side code that forces a > >> >multiple round trip. > >> > > >> >Has anyone found a way to make this work? > >> > > >> >Haile > >> > >> You want to add a button to the page, run-time? Why not add the > >> button, Visible = false and set the Visible to true when needed? > >> > >> Leon. > >> > >I am just keeping the example simple. Practical example: The web page has a > >textbox that can take filter values, and the contents of the textbox > >determine how many rows appear in an ASP:TABLE. That table can contain > >several buttons per row. There is no way to know in advance how many rows > >are to appear in the table, so the controls in the table can't be created in > >advance. > > > >I know the canned datagrid control handles this sort of scenario, but again, > >this is just an example. > > > >Thanks for taking an interest in my question. > > > >Haile > > What you want to do is hard (not even sure it will ever work) and > therefor I'd advise for the easy approach. > I've built something simular with a datagrid. I added the datagrid and > added buttons to the rows (even to be seen in design-time), the only > thing that changed when loading was the command argument for each > button. In the ItemCommand for the DataGrid even these button-events > get posted, there I check for something like > if MSG_[Id]. substring(0,3) == "MSG" then do this with that Id or even > use some column from the sender-row. > You could actually create all sorts of buttons onto the rows of the > datagrid, each command gets posted to ItemCommand eventhandler. > > An little, not-exactly-what-you-want-but-comparable, example: > > In the datagrid: > <asp:TemplateColumn HeaderText="Edit"> > <ItemStyle Width="60px"></ItemStyle> > <ItemTemplate> > <asp:ImageButton id="ImageButton1" > CausesValidation="False" CommandName="Edit" AlternateText="Edit" > > ImageUrl="../images/admin/icon-pencil.gif" > Runat="server"></asp:ImageButton><IMG src="../images/spacer.gif" > width="3"> > <asp:ImageButton id="Imagebutton2" > CausesValidation="False" CommandName="Delete" AlternateText="Delete" > > ImageUrl="../images/admin/icon-delete.gif" > Runat="server"></asp:ImageButton> > <asp:ImageButton id="Imagebutton6" > CausesValidation="False" CommandName="SortUp" AlternateText="Down" > > ImageUrl="../images/admin/icon-down.gif" > Runat="server"></asp:ImageButton> > <asp:ImageButton id="Imagebutton7" > CausesValidation="False" CommandName="SortDown" AlternateText="Up" > > ImageUrl="../images/admin/icon-up.gif" > Runat="server"></asp:ImageButton> > </ItemTemplate> > > > In the code-behind: > private void dgNewsItems_ItemCommand(object source, > System.Web.UI.WebControls.DataGridCommandEventArgs e) > { > switch (e.CommandName) > { > case "SortUp": > { > > SortIndex(Convert.ToInt32(((Label)e.Item.Cells[0].Controls[1]).Text),1); > BindData(true); > break; > } > case "SortDown": > { > > SortIndex(Convert.ToInt32(((Label)e.Item.Cells[0].Controls[1]).Text),-1); > BindData(true); > break; > } > case ... > > The Imagebuttons 6 and 7 contain the commands "SortUp" and "SortDown", > these will be handled by the ItemCommand using function SortIndex(Id, > SortChange) > > Hope this helps, > Leon.
On Mon, 29 Nov 2004 05:05:04 -0800, "haile"
[quoted text, click to view] <haile@discussions.microsoft.com> wrote: >Anyone know how to load a button and its event handler to a web page as a >result of a user action? This can't be done from Page_Load( ), because the >Page_Load event fires before the user action can set a property. And yet, if >the event handler is added at any time after Page_Load, the button doesn't >respond to events. Example: > >protected void btnUserClicksMe(o,e) >{ > // User has just clicked me, instructing a dynamic button to appear on the >page. > Button btnDynamic = new Button(); > btnDynamic += new System.EventHandler(btnDynamic_Click); > this.Controls.Add(btnDynamic); // In a practical application this would >be in a table cell or panel. >} > >protected void btnDynamic_Click(o,e) >{ > // This code should run if user clicks on the dynamically created button. > // But if event handler is declared at any time after Page_Load, this code >never runs, > // yet no compiler errors or exceptions are thrown. > Response.Write("Hi there!"); >} > >I have been attempting various workarounds to this behavior, but the only >methods that have worked have involved client-side code that forces a >multiple round trip. > >Has anyone found a way to make this work? > >Haile You want to add a button to the page, run-time? Why not add the button, Visible = false and set the Visible to true when needed?
On Mon, 29 Nov 2004 05:31:05 -0800, "haile"
[quoted text, click to view] <haile@discussions.microsoft.com> wrote: > >"Leon Friesema" wrote: > >> On Mon, 29 Nov 2004 05:05:04 -0800, "haile" >> <haile@discussions.microsoft.com> wrote: >> >> >Anyone know how to load a button and its event handler to a web page as a >> >result of a user action? This can't be done from Page_Load( ), because the >> >Page_Load event fires before the user action can set a property. And yet, if >> >the event handler is added at any time after Page_Load, the button doesn't >> >respond to events. Example: >> > >> >protected void btnUserClicksMe(o,e) >> >{ >> > // User has just clicked me, instructing a dynamic button to appear on the >> >page. >> > Button btnDynamic = new Button(); >> > btnDynamic += new System.EventHandler(btnDynamic_Click); >> > this.Controls.Add(btnDynamic); // In a practical application this would >> >be in a table cell or panel. >> >} >> > >> >protected void btnDynamic_Click(o,e) >> >{ >> > // This code should run if user clicks on the dynamically created button. >> > // But if event handler is declared at any time after Page_Load, this code >> >never runs, >> > // yet no compiler errors or exceptions are thrown. >> > Response.Write("Hi there!"); >> >} >> > >> >I have been attempting various workarounds to this behavior, but the only >> >methods that have worked have involved client-side code that forces a >> >multiple round trip. >> > >> >Has anyone found a way to make this work? >> > >> >Haile >> >> You want to add a button to the page, run-time? Why not add the >> button, Visible = false and set the Visible to true when needed? >> >> Leon. >> >I am just keeping the example simple. Practical example: The web page has a >textbox that can take filter values, and the contents of the textbox >determine how many rows appear in an ASP:TABLE. That table can contain >several buttons per row. There is no way to know in advance how many rows >are to appear in the table, so the controls in the table can't be created in >advance. > >I know the canned datagrid control handles this sort of scenario, but again, >this is just an example. > >Thanks for taking an interest in my question. > >Haile What you want to do is hard (not even sure it will ever work) and therefor I'd advise for the easy approach. I've built something simular with a datagrid. I added the datagrid and added buttons to the rows (even to be seen in design-time), the only thing that changed when loading was the command argument for each button. In the ItemCommand for the DataGrid even these button-events get posted, there I check for something like if MSG_[Id]. substring(0,3) == "MSG" then do this with that Id or even use some column from the sender-row. You could actually create all sorts of buttons onto the rows of the datagrid, each command gets posted to ItemCommand eventhandler. An little, not-exactly-what-you-want-but-comparable, example: In the datagrid: <asp:TemplateColumn HeaderText="Edit"> <ItemStyle Width="60px"></ItemStyle> <ItemTemplate> <asp:ImageButton id="ImageButton1" CausesValidation="False" CommandName="Edit" AlternateText="Edit" ImageUrl="../images/admin/icon-pencil.gif" Runat="server"></asp:ImageButton><IMG src="../images/spacer.gif" width="3"> <asp:ImageButton id="Imagebutton2" CausesValidation="False" CommandName="Delete" AlternateText="Delete" ImageUrl="../images/admin/icon-delete.gif" Runat="server"></asp:ImageButton> <asp:ImageButton id="Imagebutton6" CausesValidation="False" CommandName="SortUp" AlternateText="Down" ImageUrl="../images/admin/icon-down.gif" Runat="server"></asp:ImageButton> <asp:ImageButton id="Imagebutton7" CausesValidation="False" CommandName="SortDown" AlternateText="Up" ImageUrl="../images/admin/icon-up.gif" Runat="server"></asp:ImageButton> </ItemTemplate> In the code-behind: private void dgNewsItems_ItemCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e) { switch (e.CommandName) { case "SortUp": { SortIndex(Convert.ToInt32(((Label)e.Item.Cells[0].Controls[1]).Text),1); BindData(true); break; } case "SortDown": { SortIndex(Convert.ToInt32(((Label)e.Item.Cells[0].Controls[1]).Text),-1); BindData(true); break; } case ... The Imagebuttons 6 and 7 contain the commands "SortUp" and "SortDown", these will be handled by the ItemCommand using function SortIndex(Id, SortChange) Hope this helps,
Don't see what you're looking for? Try a search.
|
June 2003
July 2003
August 2003
September 2003
October 2003
November 2003
December 2003
January 2004
February 2004
March 2004
April 2004
May 2004
June 2004
July 2004
August 2004
September 2004
October 2004
November 2004
December 2004
January 2005
February 2005
March 2005
April 2005
May 2005
June 2005
July 2005
August 2005
September 2005
October 2005
November 2005
December 2005
January 2006
February 2006
March 2006
April 2006
May 2006
June 2006
July 2006
August 2006
September 2006
October 2006
November 2006
December 2006
January 2007
February 2007
March 2007
April 2007
May 2007
June 2007
July 2007
August 2007
September 2007
October 2007
November 2007
December 2007
January 2008
February 2008
March 2008
April 2008
May 2008
June 2008
| home · blog · groups | Questions? Comments? Contact the dn |