AutoPostBack on CheckBox control sometimes fails

If have the below markup.

<asp:checkbox id="chkTVLic" runat="server" text="TV Licence" oncheckedchanged="chkDocs_CheckChanged"
                                autopostback="true" CausesValidation="false" />
                            <asp:panel id="pnlTVLic" runat="server" visible="false">
                                <div class="toggle-item-link1 document-date">
                                    <asp:panel id="pnlTVLicIssueDate" runat="server">
                                        <p>
                                            Please enter the date of issue
                                        </p>
                                        <div class="fm-req">
                                            <asp:textbox id="txtTVLicIssueDate" cssclass="tb size2" runat="server" onblur="return true;"></asp:textbox>
                                            <cc2:calendarextender id="caleTVLicIssueDate" runat="server" targetcontrolid="txtTVLicIssueDate"
                                                popupbuttonid="ibnTVLicIssueDate" popupposition="BottomLeft" animated="true"
                                                format="dd/MM/yyyy">
                                            </cc2:calendarextender>
                                            <asp:imagebutton id="ibnTVLicIssueDate" runat="server" imageurl="../images/img-calendar-day.png"
                                                alternatetext="Calendar" tooltip="Pick Date" cssclass="date-picker" />
                                            <asp:requiredfieldvalidator id="rfvTVLicIssueDate" CssClass="error" runat="server" controltovalidate="txtTVLicIssueDate"
                                                display="Dynamic" errormessage="Required" setfocusonerror="true" validationgroup="TVLic"></asp:requiredfieldvalidator>
                                            <asp:comparevalidator id="cmvTVLicIssueDate" CssClass="error" runat="server" errormessage="Not a valid date"
                                                controltovalidate="txtTVLicIssueDate" operator="DataTypeCheck" type="Date" setfocusonerror="true"
                                                validationgroup="TVLic" display="Dynamic" cultureinvariantvalues="true"></asp:comparevalidator>
                                            <asp:customvalidator id="cuvTVLicIssueDate12Months" CssClass="error" runat="server" controltovalidate="txtTVLicIssueDate"
                                                validationgroup="TVLic" display="Dynamic" onservervalidate="cuvDocIssueDate12Months_ServerValidate"
                                                errormessage="Document must be less than 12 months old."></asp:customvalidator>
                                        </div>
                                    </asp:panel>
                                    <asp:panel id="pnlTVLicApprove" runat="server">
                                        <asp:LinkButton id="lbnTVLicApprove" runat="server" CssClass="screen-hide"
                                                alternatetext="Confirm TV Licence" tooltip="Confirm TV Licence" Text="OK" CausesValidation="false" OnClick="lbnApproveConfirm_Click"  />

                                        <asp:imagebutton id="ibnTVLicApprove" runat="server" imageurl="../images/img-accept-doc-off.png"
                                            alternatetext="Approve" tooltip="Approve" cssclass="approval-btn" causesvalidation="true" validationgroup="TVLic" OnMouseDown="HandleApproveClick('TVLic','lbnTVLicApprove');return false;" OnClientClick="HandleApproveClick('TVLic','lbnTVLicApprove');return false;" />
                                        <span class="approval-label">Accept document:</span></asp:panel>
                                </div>
                            </asp:panel>

The app is written in c# but i havn't posted any actual code as all the user code related to this markup seems to work fine.

The problem is the CheckBox chkTVLic has causes validation set to false and a开发者_运维问答utopostback set to true. So whatever happens when i check and uncheck the checkbox it should postback. Most of the time this is exactly what it does and the result is to show and hide pnlTVLic when it is checked and unchecked. However if any on the validators within the panel fire, the checkbox does not cause a postback the first time. It will on all subsequent times but never the first. However it should ALWAYS cause a postback. What could be stopping it. Before someone asks there is no use written client side code, everything is pure .net markup and c# code.

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I don't see why it shouldn't postback when you check/uncheck the checkbox, but if the only purpose of that checkbox is to hide/unhide a panel, I would rather do it in javascript. Doing a full postback to the server just for hiding some panel seems really bad.

In javascript you can do this to hide the panel:

document.getElementById('<%=pnlTVLic.ClientID%>').display='none';

And this to show it:

document.getElementById('<%=pnlTVLic.ClientID%>').display='block';

It's going to be so much faster and better. Just put a regular checkbox instead of the ASP.NET one and subscribe to the onclick event.

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Sorry, one more comment:

I think you are wrong when you say that the checkbox should ALWAYS cause a postback. No, if one of the validators fires inside the panel, the checkbox will not cause a postback until the condition is satisfied.

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This is what I did and it worked. on checkbox onclick event I disabled all the validation controls and immediately did Page_ClientValidate(); and it worked.