error in adding user controls at runtime

Discussion in 'ASP .Net' started by rushikesh.joshi@gmail.com, Mar 30, 2006.

  1. Guest

    Hi All,

    I have created my own WebControl and want to add it in my aspx page at
    runtime.

    it's compiling perfectly, but when i m going to execute, it gives me
    error of "Object reference not set to an instance of an object." in my
    server control (ascx.cs file)


    There is a table in my user control with id "tdCell".

    I'm creating a Label control at runtime in Page_Load of user control,
    and want to add it in the "tdCell" by just tdCell.Controls.Add()....

    There is a Panel on my aspx page with id "TBarPanel", and want to add
    the user control at runtime. but i m getting error.

    Any idea...I tried panel/placeholder/table every thing but it's not
    working.
    I also tried using LoadControl("MyControl.ascx"), but it's also not
    working.


    I put all code and error string for your reference.

    Thanks & Regards,
    Rushikesh




    ////////// MyControl.ascx /////////////


    <%@ Control Language="C#" AutoEventWireup="true"
    CodeFile="MyControl.ascx.cs" Inherits="MyControl" %>

    <table cellpadding="0" cellspacing="0">
    <tr>
    <td id="tdCell" runat="server"></td>
    </tr>
    </table>




    ////////// MyControl.ascx.cs /////////////

    using System;
    using System.Data;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using System.Web.UI.WebControls.WebParts;
    using System.Web.UI.HtmlControls;

    public partial class MyControl: System.Web.UI.UserControl
    {

    protected void Page_Load(object sender, EventArgs e)
    {
    Label lbl = new Label();
    lbl.Text = "Hello";
    tdCell.Controls.Add(lbl);

    }
    }


    //// //// MyControl_Test.aspx /////////

    <%@ Page Language="C#" AutoEventWireup="true"
    CodeFile="MyControl_Test.aspx.cs" Inherits="MyControl_Test" %>

    <%@ Register Src="MyControl.ascx" TagName="MyControl" TagPrefix="uc1"
    %>

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

    <html xmlns="http://www.w3.org/1999/xhtml" >
    <head runat="server">
    <title>Untitled Page</title>
    </head>
    <body>
    <form id="form1" runat="server">
    <div>
    <asp:panel ID="TBarPanel" runat="server" Height="42px"
    Width="100%">
    </asp:panel>
    </form>
    </body>
    </html>



    //// //// MyControl_Test.aspx.cs /////////

    using System;
    using System.Data;
    using System.Configuration;
    using System.Collections;
    using System.Web;
    using System.Web.Security;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using System.Web.UI.WebControls.WebParts;
    using System.Web.UI.HtmlControls;


    public partial class TimeBarCtrl_Test : System.Web.UI.Page
    {
    protected void Page_Load(object sender, EventArgs e)
    {
    MyControl myctrl1 = new MyControl();
    placeUserControls.AddTimeBarSegment(myctrl1);

    MyControl myctrl2 = new MyControl();
    placeUserControls.AddTimeBarSegment(myctrl2);

    MyControl myctrl3 = new MyControl();
    placeUserControls.AddTimeBarSegment(myctrl3);

    }
    }





    ////////////////////**********************Error

    Object reference not set to an instance of an object.

    Description: An unhandled exception occurred during the execution of
    the current web request. Please review the stack trace for more
    information about the error and where it originated in the code.

    Exception Details: System.NullReferenceException: Object reference not
    set to an instance of an object.

    Source Error:


    Line 54: Label lbl = new Label();
    Line 55: lbl.Text = "Hello";
    Line 56: tdCell.Controls.Add(lbl);
    Line 57:
    Line 58:


    Source File: d:\inetpub\wwwroot\MACT\Interface\TimeBarCtrl.ascx.cs
    Line: 56

    Stack Trace:


    [NullReferenceException: Object reference not set to an instance of an
    object.]
    TimeBarCtrl.Page_Load(Object sender, EventArgs e) in
    d:\inetpub\wwwroot\MACT\Interface\TimeBarCtrl.ascx.cs:56
    System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object
    o, Object t, EventArgs e) +13
    System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object
    sender, EventArgs e) +45
    System.Web.UI.Control.OnLoad(EventArgs e) +80
    System.Web.UI.Control.LoadRecursive() +49
    System.Web.UI.Control.LoadRecursive() +132
    System.Web.UI.Control.LoadRecursive() +132
    System.Web.UI.Control.LoadRecursive() +132
    System.Web.UI.Page.ProcessRequestMain(Boolean
    includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
    +3710
     
    , Mar 30, 2006
    #1
    1. Advertising

  2. More code would be helpful.

    It should look something:

    Control c = Page.LoadControl("controlFileName.ascx");
    tdCell.Controls.Add(c);

    From the brief description you've given, it looks like the error might
    actually be happening in your contorl (you say the object reference is
    occuring in an ascx file) so it's really hard to tell what exactly is going
    on.

    Karl


    --
    http://www.openmymind.net/
    http://www.fuelindustries.com/


    <> wrote in message
    news:...
    > Hi All,
    >
    > I have created my own WebControl and want to add it in my aspx page at
    > runtime.
    >
    > it's compiling perfectly, but when i m going to execute, it gives me
    > error of "Object reference not set to an instance of an object." in my
    > server control (ascx.cs file)
    >
    >
    > There is a table in my user control with id "tdCell".
    >
    > I'm creating a Label control at runtime in Page_Load of user control,
    > and want to add it in the "tdCell" by just tdCell.Controls.Add()....
    >
    > There is a Panel on my aspx page with id "TBarPanel", and want to add
    > the user control at runtime. but i m getting error.
    >
    > Any idea...I tried panel/placeholder/table every thing but it's not
    > working.
    > I also tried using LoadControl("MyControl.ascx"), but it's also not
    > working.
    >
    >
    > I put all code and error string for your reference.
    >
    > Thanks & Regards,
    > Rushikesh
    >
    >
    >
    >
    > ////////// MyControl.ascx /////////////
    >
    >
    > <%@ Control Language="C#" AutoEventWireup="true"
    > CodeFile="MyControl.ascx.cs" Inherits="MyControl" %>
    >
    > <table cellpadding="0" cellspacing="0">
    > <tr>
    > <td id="tdCell" runat="server"></td>
    > </tr>
    > </table>
    >
    >
    >
    >
    > ////////// MyControl.ascx.cs /////////////
    >
    > using System;
    > using System.Data;
    > using System.Web.UI;
    > using System.Web.UI.WebControls;
    > using System.Web.UI.WebControls.WebParts;
    > using System.Web.UI.HtmlControls;
    >
    > public partial class MyControl: System.Web.UI.UserControl
    > {
    >
    > protected void Page_Load(object sender, EventArgs e)
    > {
    > Label lbl = new Label();
    > lbl.Text = "Hello";
    > tdCell.Controls.Add(lbl);
    >
    > }
    > }
    >
    >
    > //// //// MyControl_Test.aspx /////////
    >
    > <%@ Page Language="C#" AutoEventWireup="true"
    > CodeFile="MyControl_Test.aspx.cs" Inherits="MyControl_Test" %>
    >
    > <%@ Register Src="MyControl.ascx" TagName="MyControl" TagPrefix="uc1"
    > %>
    >
    > <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    > "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    >
    > <html xmlns="http://www.w3.org/1999/xhtml" >
    > <head runat="server">
    > <title>Untitled Page</title>
    > </head>
    > <body>
    > <form id="form1" runat="server">
    > <div>
    > <asp:panel ID="TBarPanel" runat="server" Height="42px"
    > Width="100%">
    > </asp:panel>
    > </form>
    > </body>
    > </html>
    >
    >
    >
    > //// //// MyControl_Test.aspx.cs /////////
    >
    > using System;
    > using System.Data;
    > using System.Configuration;
    > using System.Collections;
    > using System.Web;
    > using System.Web.Security;
    > using System.Web.UI;
    > using System.Web.UI.WebControls;
    > using System.Web.UI.WebControls.WebParts;
    > using System.Web.UI.HtmlControls;
    >
    >
    > public partial class TimeBarCtrl_Test : System.Web.UI.Page
    > {
    > protected void Page_Load(object sender, EventArgs e)
    > {
    > MyControl myctrl1 = new MyControl();
    > placeUserControls.AddTimeBarSegment(myctrl1);
    >
    > MyControl myctrl2 = new MyControl();
    > placeUserControls.AddTimeBarSegment(myctrl2);
    >
    > MyControl myctrl3 = new MyControl();
    > placeUserControls.AddTimeBarSegment(myctrl3);
    >
    > }
    > }
    >
    >
    >
    >
    >
    > ////////////////////**********************Error
    >
    > Object reference not set to an instance of an object.
    >
    > Description: An unhandled exception occurred during the execution of
    > the current web request. Please review the stack trace for more
    > information about the error and where it originated in the code.
    >
    > Exception Details: System.NullReferenceException: Object reference not
    > set to an instance of an object.
    >
    > Source Error:
    >
    >
    > Line 54: Label lbl = new Label();
    > Line 55: lbl.Text = "Hello";
    > Line 56: tdCell.Controls.Add(lbl);
    > Line 57:
    > Line 58:
    >
    >
    > Source File: d:\inetpub\wwwroot\MACT\Interface\TimeBarCtrl.ascx.cs
    > Line: 56
    >
    > Stack Trace:
    >
    >
    > [NullReferenceException: Object reference not set to an instance of an
    > object.]
    > TimeBarCtrl.Page_Load(Object sender, EventArgs e) in
    > d:\inetpub\wwwroot\MACT\Interface\TimeBarCtrl.ascx.cs:56
    > System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object
    > o, Object t, EventArgs e) +13
    > System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object
    > sender, EventArgs e) +45
    > System.Web.UI.Control.OnLoad(EventArgs e) +80
    > System.Web.UI.Control.LoadRecursive() +49
    > System.Web.UI.Control.LoadRecursive() +132
    > System.Web.UI.Control.LoadRecursive() +132
    > System.Web.UI.Control.LoadRecursive() +132
    > System.Web.UI.Page.ProcessRequestMain(Boolean
    > includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
    > +3710
    >
     
    Karl Seguin [MVP], Mar 30, 2006
    #2
    1. Advertising

  3. Guest

    Hi Karl,

    Thankyou for quick response.

    Yes you are right, there might be some problem in my user control.

    But it seems ok, there is tdCell id and my MyControl.ascx page and i m
    trying to add some label control by just tdCell.Controls.Add(lbl).

    this is working perfectly in ASPX file but this is not working in ASCX.

    Thanks
    Rushikesh
     
    , Mar 30, 2006
    #3
  4. Guest

    , Mar 30, 2006
    #4
  5. Patrice Guest

    Looks like tdCell is null.

    --
    Patrice

    <> a écrit dans le message de news:
    ...
    > Hi Karl,
    >
    > Thankyou for quick response.
    >
    > Yes you are right, there might be some problem in my user control.
    >
    > But it seems ok, there is tdCell id and my MyControl.ascx page and i m
    > trying to add some label control by just tdCell.Controls.Add(lbl).
    >
    > this is working perfectly in ASPX file but this is not working in ASCX.
    >
    > Thanks
    > Rushikesh
    >
     
    Patrice, Mar 30, 2006
    #5
    1. Advertising

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