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Posted 11 Feb 2014

ASP.NET CheckBoxList Client Side Validation using JavaScript

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In this blog, we will explore a trick to validate whether any CheckBox inside one CheckBoxList is checked or not.

ASP.NET CheckBox Validation Nothing Checked

ASP.NET CheckBox Validation Nothing Checked

ASP.NET CheckBox Validation Atleast one Checked

ASP.NET CheckBox Validation Atleast one Checked


In this blog, we will explore a trick to validate whether any CheckBox inside one CheckBoxList is checked or not.


When you define one CheckBoxList on aspx page by writing code something like below…

<asp:CheckBoxList RepeatDirection="Horizontal" 


    <asp:ListItem Text="Apples" Value="1"></asp:ListItem>
    <asp:ListItem Text="Oranges" Value="2"></asp:ListItem>
    <asp:ListItem Text="Mangoes" Value="3"></asp:ListItem>
</asp:CheckBoxList> will render on browser like below…

<table id="chkDemo">
                <input type="checkbox" value="1" name="chkDemo$0" id="chkDemo_0">
                <label for="chkDemo_0">Apples</label>
                <input type="checkbox" value="2" name="chkDemo$1" id="chkDemo_1">
                <label for="chkDemo_1">Oranges</label>
                <input type="checkbox" value="3" name="chkDemo$2" id="chkDemo_2">
                <label for="chkDemo_2">Mangoes</label>

Basically, it renders number of CheckBoxes depending on the number of ListItems inside CheckBoxList.

So, What Is the Logic Here?

We will call one JavaScript function on a Button Click.
Button would look like…

<asp:Button runat="server" ID="Button1" Text="Submit" 

            OnClientClick="return validateCheckBoxList();" />

Inside that function, we will run the following logic to validate whether any CheckBox is checked or not.

  1. We will find the main CheckBoxList first, which is rendered as a Table.
  2. Next, we need to find all the CheckBoxes inside that Table.
  3. After that, we have to check if any CheckBox is checked by looping through them.
  4. If any CheckBox is checked, then break the Loop and show alert (for demo purpose).
  5. Return true if any CheckBox is checked, else show alert and return false.
function validateCheckBoxList() {
    var isAnyCheckBoxChecked = false;

    // ::: Step-1 & 2 ::: Let's get all the CheckBoxes inside the CheckBoxList.
    var checkBoxes = document.getElementById("chkDemo").getElementsByTagName("input");
    // ::: NOTE ::: For jsfiddle demo I have directly used the ID. 
    // Otherwise you might have to use ClientID like below...
    // document.getElementById
    // ("<%= chkDemo.ClientID %>").getElementsByTagName("input");

    // ::: Step-3 ::: Now let's Loop through the Children.
    for (var i = 0; i < checkBoxes.length; i++) {
        if (checkBoxes[i].type == "checkbox") {
            if (checkBoxes[i].checked) {
                // ::: Step-4 ::: If current CheckBox is checked, then show alert.
                // Break the Loop.
                isAnyCheckBoxChecked = true;
                alert("Atleast one CheckBox is checked");
    // ::: Step-5 ::: Check if any CheckBox is checked or not.
    // Show alert and return accordingly.
    if (!isAnyCheckBoxChecked) {
        alert("No CheckBox is Checked.");

    return isAnyCheckBoxChecked;

See the Demo



I have used the CheckBoxList ID directly, which is chkDemo. But when your ClientID changes, you can get the CheckBoxList like…

document.getElementById("<%= chkDemo.ClientID %>");

Do You Find It Interesting?

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ)
Software Developer Mindfire Solutions
India India
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Currently working @Mindfire Solutions.
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Comments and Discussions

GeneralNice one Pin
Member 1338498229-Aug-17 21:03
memberMember 1338498229-Aug-17 21:03 
QuestionGood explained dude!,,, My vote for 5 ! Pin
Sujee116-Feb-14 5:22
memberSujee116-Feb-14 5:22 
AnswerRe: Good explained dude!,,, My vote for 5 ! Pin
Tadit Dash16-Feb-14 7:14
protectorTadit Dash16-Feb-14 7:14 
GeneralMy vote is 5 Pin
joginder-banger13-Feb-14 8:58
memberjoginder-banger13-Feb-14 8:58 
GeneralRe: My vote is 5 Pin
Tadit Dash13-Feb-14 17:30
protectorTadit Dash13-Feb-14 17:30 
GeneralMy vote of 5 Pin
Carsten V2.012-Feb-14 21:53
memberCarsten V2.012-Feb-14 21:53 
GeneralRe: My vote of 5 Pin
Tadit Dash12-Feb-14 23:35
mvpTadit Dash12-Feb-14 23:35 

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