Problem with Javascript in a UserControl

Discussion in 'ASP .Net' started by tshad, Jun 28, 2006.

  1. tshad

    tshad Guest

    I get an error when running my Javascript inside my UserControl. It works
    fine if I put the UserControl Data directly in my Web Page.

    The stripped down code is:

    <script language=javascript>
    function CheckQuestion()
    {
    var checkBox = document.getElementById('SecurityStandard');
    alert("checkBox.checked = " + checkBox.checked);
    }
    </script>

    Mozilla doesn't seem to have a problem, but IE gives me this error:

    Error: Object required.

    The object in the UserControl is:

    <asp:RadioButton ID="SecurityStandard" Checked="true"
    GroupName="SecurityQuestion" runat="server" Text=" Secret Question:"/>

    From View Source:

    <input id="_ctl0_SecurityStandard" type="radio"
    name="_ctl0:SecurityQuestion" value="SecurityStandard" checked="checked"
    onclick="return CheckQuestion();" />

    On the page that does work:

    <input id="SecurityStandard" type="radio" name="SecurityQuestion"
    value="SecurityStandard" checked="checked" onclick="return CheckQuestion();"
    />

    For some reason the radio buttons Name is appended with "_ctl0:" in the
    UserControl and nothing is appended in the regular page.

    I am used to seeing this from DataGrids, but not as a regular control on the
    page.

    How would I hande the Javascript in this case?

    Thanks,

    Tom
    tshad, Jun 28, 2006
    #1
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  2. tshad

    John Prado Guest

    Make a look at the HTML generated by your code and find your checkbox ID.

    Did it looks some diferent from the original??? Sure it is.

    The framework add the name of the control to input ids in generated HTML.

    That's why your javascript don't works.




    tshad wrote:
    > I get an error when running my Javascript inside my UserControl. It works
    > fine if I put the UserControl Data directly in my Web Page.
    >
    > The stripped down code is:
    >
    > <script language=javascript>
    > function CheckQuestion()
    > {
    > var checkBox = document.getElementById('SecurityStandard');
    > alert("checkBox.checked = " + checkBox.checked);
    > }
    > </script>
    >
    > Mozilla doesn't seem to have a problem, but IE gives me this error:
    >
    > Error: Object required.
    >
    > The object in the UserControl is:
    >
    > <asp:RadioButton ID="SecurityStandard" Checked="true"
    > GroupName="SecurityQuestion" runat="server" Text=" Secret Question:"/>
    >
    > From View Source:
    >
    > <input id="_ctl0_SecurityStandard" type="radio"
    > name="_ctl0:SecurityQuestion" value="SecurityStandard" checked="checked"
    > onclick="return CheckQuestion();" />
    >
    > On the page that does work:
    >
    > <input id="SecurityStandard" type="radio" name="SecurityQuestion"
    > value="SecurityStandard" checked="checked" onclick="return CheckQuestion();"
    > />
    >
    > For some reason the radio buttons Name is appended with "_ctl0:" in the
    > UserControl and nothing is appended in the regular page.
    >
    > I am used to seeing this from DataGrids, but not as a regular control on the
    > page.
    >
    > How would I hande the Javascript in this case?
    >
    > Thanks,
    >
    > Tom
    >
    >
    John Prado, Jun 28, 2006
    #2
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  3. The reason this script doesn't work is because of you are using an user
    control. Generally, .NET appends this _ct* prefix with the controls that
    placed in a UserControl and UserControl placed in a page, which is to
    make uniqueness among the controls present in the UserControl and in the
    Page.

    The solution to this problem is you have to place this script in your
    code behind file's Page_Load event. Check the below code.


    protected void Page_Load(object sender, EventArgs e)
    {
    if (!IsPostBack)
    {

    String _Script = "function CheckQuestion()";
    _Script += "{";
    _Script += "var checkBox = document.getElementById({0});";
    _Script += "alert(checkBox.checked)";
    _Script += "}";

    // Assume you have the RadioButton already defined
    _Script = String.Format(_Script, SecurityStandard.ClientId);

    Page.ClientScript.RegisterStartupScript(this.GetType(),
    "CheckBox_Script", _Script, true);

    }

    }

    For your understanding, the trick part is

    _Script = String.Format(_Script, SecurityStandard.ClientId);

    I am just updating the ASP.NET generated control id to the script,
    instead of the one it has in the design time. By using
    RegisterStartupScript I am registering the script to the client.

    Let me know if you have further issues with the code.

    -
    Vadivel Kumar
    http://vadivelk.net

    Note: This solution will only work in .NET 2.0, Let me know if you are
    looking for .NET 1.1




    tshad wrote:
    > I get an error when running my Javascript inside my UserControl. It works
    > fine if I put the UserControl Data directly in my Web Page.
    >
    > The stripped down code is:
    >
    > <script language=javascript>
    > function CheckQuestion()
    > {
    > var checkBox = document.getElementById('SecurityStandard');
    > alert("checkBox.checked = " + checkBox.checked);
    > }
    > </script>
    >
    > Mozilla doesn't seem to have a problem, but IE gives me this error:
    >
    > Error: Object required.
    >
    > The object in the UserControl is:
    >
    > <asp:RadioButton ID="SecurityStandard" Checked="true"
    > GroupName="SecurityQuestion" runat="server" Text=" Secret Question:"/>
    >
    > From View Source:
    >
    > <input id="_ctl0_SecurityStandard" type="radio"
    > name="_ctl0:SecurityQuestion" value="SecurityStandard" checked="checked"
    > onclick="return CheckQuestion();" />
    >
    > On the page that does work:
    >
    > <input id="SecurityStandard" type="radio" name="SecurityQuestion"
    > value="SecurityStandard" checked="checked" onclick="return CheckQuestion();"
    > />
    >
    > For some reason the radio buttons Name is appended with "_ctl0:" in the
    > UserControl and nothing is appended in the regular page.
    >
    > I am used to seeing this from DataGrids, but not as a regular control on the
    > page.
    >
    > How would I hande the Javascript in this case?
    >
    > Thanks,
    >
    > Tom
    >
    >
    Vadivel Kumar, Jun 28, 2006
    #3
  4. tshad

    tshad Guest

    Why do you have to Register the script? I use Javascript all the time and I
    don't register it.

    Also, how does document.getElementById({0}) get you the Radio button?

    I actually have about 15 objects (texboxes and other radio buttons). How
    does it know what control you are talking about?

    What actually prepends the "_ctl0:" to the ID?

    Thanks,

    Tom

    "Vadivel Kumar" <> wrote in message
    news:...
    > The reason this script doesn't work is because of you are using an user
    > control. Generally, .NET appends this _ct* prefix with the controls that
    > placed in a UserControl and UserControl placed in a page, which is to make
    > uniqueness among the controls present in the UserControl and in the Page.
    >
    > The solution to this problem is you have to place this script in your code
    > behind file's Page_Load event. Check the below code.
    >
    >
    > protected void Page_Load(object sender, EventArgs e)
    > {
    > if (!IsPostBack)
    > {
    >
    > String _Script = "function CheckQuestion()";
    > _Script += "{";
    > _Script += "var checkBox = document.getElementById({0});";
    > _Script += "alert(checkBox.checked)";
    > _Script += "}";
    >
    > // Assume you have the RadioButton already defined
    > _Script = String.Format(_Script, SecurityStandard.ClientId);
    >
    > Page.ClientScript.RegisterStartupScript(this.GetType(),
    > "CheckBox_Script", _Script, true);
    >
    > }
    >
    > }
    >
    > For your understanding, the trick part is
    >
    > _Script = String.Format(_Script, SecurityStandard.ClientId);
    >
    > I am just updating the ASP.NET generated control id to the script, instead
    > of the one it has in the design time. By using RegisterStartupScript I am
    > registering the script to the client.
    >
    > Let me know if you have further issues with the code.
    >
    > -
    > Vadivel Kumar
    > http://vadivelk.net
    >
    > Note: This solution will only work in .NET 2.0, Let me know if you are
    > looking for .NET 1.1
    >
    >
    >
    >
    > tshad wrote:
    >> I get an error when running my Javascript inside my UserControl. It
    >> works fine if I put the UserControl Data directly in my Web Page.
    >>
    >> The stripped down code is:
    >>
    >> <script language=javascript>
    >> function CheckQuestion()
    >> {
    >> var checkBox = document.getElementById('SecurityStandard');
    >> alert("checkBox.checked = " + checkBox.checked);
    >> }
    >> </script>
    >>
    >> Mozilla doesn't seem to have a problem, but IE gives me this error:
    >>
    >> Error: Object required.
    >>
    >> The object in the UserControl is:
    >>
    >> <asp:RadioButton ID="SecurityStandard" Checked="true"
    >> GroupName="SecurityQuestion" runat="server" Text=" Secret Question:"/>
    >>
    >> From View Source:
    >>
    >> <input id="_ctl0_SecurityStandard" type="radio"
    >> name="_ctl0:SecurityQuestion" value="SecurityStandard" checked="checked"
    >> onclick="return CheckQuestion();" />
    >>
    >> On the page that does work:
    >>
    >> <input id="SecurityStandard" type="radio" name="SecurityQuestion"
    >> value="SecurityStandard" checked="checked" onclick="return
    >> CheckQuestion();" />
    >>
    >> For some reason the radio buttons Name is appended with "_ctl0:" in the
    >> UserControl and nothing is appended in the regular page.
    >>
    >> I am used to seeing this from DataGrids, but not as a regular control on
    >> the page.
    >>
    >> How would I hande the Javascript in this case?
    >>
    >> Thanks,
    >>
    >> Tom
    tshad, Jun 28, 2006
    #4
  5. Hi,

    tshad wrote:
    > Why do you have to Register the script? I use Javascript all the time and I
    > don't register it.


    When you "register" a script in a Page instance, you make sure that this
    script will appear only once on the page, even if there are more
    instances of the same control. If you don't register the script, and if
    you have more than one instance of the same control, then each instance
    will generate the same script, which is not needed, might cause unwanted
    effects, and makes the response bigger for no reason.

    > Also, how does document.getElementById({0}) get you the Radio button?


    document.getElementById takes a string (ID) as parameter. However, the
    ID must be carefully used, because in a control, it might not be equal
    to the ID set in the code. Once again, if you have more than one
    instance of the same control, the ID must be unique. This is why ASP.NET
    generates a unique ID, which is accessible with the ClientID property.

    The syntax String.Format( "document.getElementById({0})",
    SecurityStandard.ClientID ) will simply replace the {0} element with
    the first parameter after the string, in this case the ClientID of the
    SecurityStandard control.

    > I actually have about 15 objects (texboxes and other radio buttons). How
    > does it know what control you are talking about?


    I don't understand your question.

    > What actually prepends the "_ctl0:" to the ID?


    See my explanation above: It's ASP.NET because of the need for the ID to
    be unique.


    > Thanks,
    >
    > Tom


    HTH,
    Laurent
    --
    Laurent Bugnion, GalaSoft
    Software engineering: http://www.galasoft-LB.ch
    Private/Malaysia: http://mypage.bluewin.ch/lbugnion
    Support children in Calcutta: http://www.calcutta-espoir.ch
    Laurent Bugnion, Jun 28, 2006
    #5
  6. Thanks Laurent, for the explanation behalf of me.

    --
    Vadivel Kumar
    http://www.vadivelk.net
    (remove "online.")

    Laurent Bugnion wrote:
    > Hi,
    >
    > tshad wrote:
    >> Why do you have to Register the script? I use Javascript all the time
    >> and I don't register it.

    >
    > When you "register" a script in a Page instance, you make sure that this
    > script will appear only once on the page, even if there are more
    > instances of the same control. If you don't register the script, and if
    > you have more than one instance of the same control, then each instance
    > will generate the same script, which is not needed, might cause unwanted
    > effects, and makes the response bigger for no reason.
    >
    >> Also, how does document.getElementById({0}) get you the Radio button?

    >
    > document.getElementById takes a string (ID) as parameter. However, the
    > ID must be carefully used, because in a control, it might not be equal
    > to the ID set in the code. Once again, if you have more than one
    > instance of the same control, the ID must be unique. This is why ASP.NET
    > generates a unique ID, which is accessible with the ClientID property.
    >
    > The syntax String.Format( "document.getElementById({0})",
    > SecurityStandard.ClientID ) will simply replace the {0} element with
    > the first parameter after the string, in this case the ClientID of the
    > SecurityStandard control.
    >
    >> I actually have about 15 objects (texboxes and other radio buttons).
    >> How does it know what control you are talking about?

    >
    > I don't understand your question.
    >
    >> What actually prepends the "_ctl0:" to the ID?

    >
    > See my explanation above: It's ASP.NET because of the need for the ID to
    > be unique.
    >
    >
    >> Thanks,
    >>
    >> Tom

    >
    > HTH,
    > Laurent
    Vadivel Kumar, Jun 29, 2006
    #6
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