How do I make a checkbox required on an ASP NET form

Question

I ve done some searching on this  and I ve found several partial answers  however nothing that gives me that warm fuzzy  this is the right way to do this   To answer the most frequently occurring complaint against this question   checkboxes can have two legitimate states - checked and unchecked   this is an  I accept the terms and conditions     checkbox which must be checked in order to complete a registration  hence checking the box is required from a business logic standpoint   Please provide complete cut-n-paste ready code fragments with your response  I know there are several pieces to this -- the CustomValidator  presumably   the code-behind  some javascript and possibly a check for IsValid  and the frustrating part for me is that in each example I ve seen  one of these critical pieces is missing

User · Answer

Scott s answer will work for classes of checkboxes   If you want individual checkboxes  you have to be a little sneakier   If you re just doing one box  it s better to do it with IDs   This example does it by specific check boxes and doesn t require jQuery   It s also a nice little example of how you can get those pesky control IDs into your Javascript   The  ascx    lt script type  text javascript  gt       function checkAgreement source  args                                var elem   document getElementById   lt    chkAgree ClientID   gt             if  elem checked                        args IsValid   true                    else                               args IsValid   false                       function checkAge source  args                var elem   document getElementById   lt    chkAge ClientID   gt             if  elem checked                        args IsValid   true                    else                       args IsValid   false                        lt  script gt    lt asp CheckBox ID  chkAgree  runat  server    gt   lt asp Label AssociatedControlID  chkAgree  runat  server  gt I agree to the lt  asp Label gt   lt asp HyperLink ID  lnkTerms  runat  server  gt Terms  amp  Conditions lt  asp HyperLink gt   lt asp Label AssociatedControlID  chkAgree  runat  server  gt   lt  asp Label gt   lt br   gt    lt asp CustomValidator ID  chkAgreeValidator  runat  server  Display  Dynamic      ClientValidationFunction  checkAgreement  gt      You must agree to the terms and conditions       lt  asp CustomValidator gt    lt asp CheckBox ID  chkAge  runat  server    gt   lt asp Label AssociatedControlID  chkAge  runat  server  gt I certify that I am at least 18 years of age  lt  asp Label gt           lt asp CustomValidator ID  chkAgeValidator  runat  server  Display  Dynamic      ClientValidationFunction  checkAge  gt      You must be 18 years or older to continue       lt  asp CustomValidator gt    And the codebehind   Protected Sub chkAgreeValidator ServerValidate ByVal sender As Object  ByVal e As System Web UI WebControls ServerValidateEventArgs    Handles chkAgreeValidator ServerValidate     e IsValid   chkAgree Checked End Sub  Protected Sub chkAgeValidator ServerValidate ByVal sender As Object  ByVal e As System Web UI WebControls ServerValidateEventArgs    Handles chkAgeValidator ServerValidate     e IsValid   chkAge Checked End Sub

User · Answer

Non-javascript way       aspx page     lt form id  form1  runat  server  gt   lt div gt       lt asp CheckBox ID  CheckBox1  runat  server    gt       lt asp CustomValidator ID  CustomValidator1          runat  server  ErrorMessage  CustomValidator  ControlToValidate  CheckBox1  gt  lt  asp CustomValidator gt   lt  div gt   lt  form gt    Code Behind   Protected Sub CustomValidator1 ServerValidate ByVal source As Object  ByVal args As System Web UI WebControls ServerValidateEventArgs  Handles CustomValidator1 ServerValidate     If Not CheckBox1 Checked Then         args IsValid   False     End If End Sub   For any actions you might need  business Rules    If Page IsValid Then     do logic End If    Sorry for the VB code       you can convert it to C  if that is your pleasure   The company I am working for right now requires VB

User · Answer

I typically perform the validation on the client side    lt asp checkbox id  chkTerms  text   I agree to the terms  ValidationGroup  vg  runat  Server     gt   lt asp CustomValidator id  vTerms                  ClientValidationFunction  validateTerms                   ErrorMessage   lt br  gt Terms and Conditions are required                    ForeColor  Red                  Display  Static                  EnableClientScript  true                  ValidationGroup  vg                  runat  server   gt    lt asp Button ID  btnSubmit  OnClick  btnSubmit Click  CausesValidation  true  Text  Submit  ValidationGroup  vg  runat  server    gt    lt script gt      function validateTerms source  arguments            var  c        lt    chkTerms ClientID   gt             if  c prop  checked                 arguments IsValid   true            else               arguments IsValid   false                   lt  script gt

User · Answer

If you want a true validator that does not rely on jquery and handles server side validation as well   and you should  server side validation is the most important part  then here is a control  public class RequiredCheckBoxValidator   System Web UI WebControls BaseValidator       private System Web UI WebControls CheckBox  ctrlToValidate   null      protected System Web UI WebControls CheckBox CheckBoxToValidate               get                       if   ctrlToValidate    null                   ctrlToValidate   FindControl this ControlToValidate  as System Web UI WebControls CheckBox               return  ctrlToValidate                       protected override bool ControlPropertiesValid                 if  this ControlToValidate Length    0              throw new System Web HttpException string Format  The ControlToValidate property of   0   is required    this ID             if  this CheckBoxToValidate    null              throw new System Web HttpException string Format  This control can only validate CheckBox               return true             protected override bool EvaluateIsValid                 return CheckBoxToValidate Checked             protected override void OnPreRender EventArgs e                base OnPreRender e            if  this Visible  amp  amp  this Enabled                        System Web UI ClientScriptManager cs   this Page ClientScript              if  this DetermineRenderUplevel    amp  amp  this EnableClientScript                                cs RegisterExpandoAttribute this ClientID   evaluationfunction    cb verify   false                             if   this Page ClientScript IsClientScriptBlockRegistered this GetType   FullName                                 cs RegisterClientScriptBlock this GetType    this GetType   FullName  GetClientSideScript                                         private string GetClientSideScript                 return    lt script language   javascript   gt function cb verify sender   var cntrl   document getElementById sender controltovalidate  return cntrl checked   lt  script gt

User · Answer

javascript function for client side validation  using jQuery      function CheckBoxRequired ClientValidate sender  e        e IsValid   jQuery   AcceptedAgreement input checkbox   is   checked        code-behind for server side validation     protected void CheckBoxRequired ServerValidate object sender  ServerValidateEventArgs e        e IsValid   MyCheckBox Checked      ASP Net code for the checkbox  amp  validator      lt asp CheckBox runat  server  ID  MyCheckBox  CssClass  AcceptedAgreement    gt   lt asp CustomValidator runat  server  ID  CheckBoxRequired  EnableClientScript  true      OnServerValidate  CheckBoxRequired ServerValidate      ClientValidationFunction  CheckBoxRequired ClientValidate  gt You must select this box to proceed  lt  asp CustomValidator gt    and finally  in your postback - whether from a button or whatever     if  Page IsValid           your code here

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C  version of andrew s answer    lt asp CustomValidator ID  CustomValidator1  runat  server           ErrorMessage  Please accept the terms              onservervalidate  CustomValidator1 ServerValidate  gt  lt  asp CustomValidator gt       lt asp CheckBox ID  CheckBox1  runat  server    gt    Code-behind   protected void CustomValidator1 ServerValidate object source  ServerValidateEventArgs args        args IsValid   CheckBox1 Checked

[asp.net] How do I make a checkbox required on an ASP.NET form?

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