display alert when radio button is not selected

Could you try this..

<script type="text/javascript">
    function as()
    {
        if(!document.getElementById('<%=RadioBtn.ClientID %>_0').checked)
        {
        alert("check the field");
        }
    }
    </script>

<asp:radiobuttonlist id="RadioBtn" runat="server" repeatdirection="Horizontal" xmlns:asp="#unknown">
            <asp:listitem>Male</asp:listitem>
            <asp:listitem>Female</asp:listitem>
        </asp:radiobuttonlist>
        
        <asp:button id="Button1" runat="server" text="Button" onclientclick="as();" xmlns:asp="#unknown" />

Thanks

The problem is the HTML code generated for ASP.NET code

<table id="RadioBtn" border="0">
            <tr>
                <td>
                    <input id="RadioBtn_0" type="radio" name="RadioBtn" value="Male" /><label for="RadioBtn_0">Male</label>
                </td>
                <td>
                    <input id="RadioBtn_1" type="radio" name="RadioBtn" value="Female" /><label for="RadioBtn_1">Female</label>
                </td>
            </tr>
        </table>
        <input type="submit" name="Button1" value="" onclick="as();" id="Submit1" />

you see everything in ASP.NET will be rendered to HTML for client and you will get above. if the above RadioButtonList control is inside some other control or you have master page the ID of the table will be different and when you are trying to document.getElementById(...) it results in undefined.

Always make sure your javascript is aligned with the client code generated for ASP.net code. you can do right click > view source in web browser.

To solve it replace your javascript code with below code

<script type="text/javascript">
    function as()
    {
        //Get the client ID of the control
        var tableID = '<%= RadioBtn.ClientID %>';
        var radioButtons = document.getElementsByName(tableID)
        var totalRows = radioButtons.length;
        var radioButton;
        var flagRadioButtonChecked = false;
        for(var rowIndex=0; rowIndex< totalRows; rowIndex++)
        {
            radioButton = radioButtons[rowIndex]
            //Check if it's a radio button
            if(radioButton.type == 'radio')
            {
                //Check if it's checked
                if(radioButton.checked)
                {
                    //current radio button is checked
                    flagRadioButtonChecked=true;
                    //breaking from here will keep reference of checked radio button to radioButton variable
                    break;
                }
            }
        }
        //Check if any radio button is checked
        if(flagRadioButtonChecked)
        {
            alert(radioButton.value + ' is checked...');
        }
    }
    </script>

Hope this will help.

Thanks,
Hemant

Hi its very easy

try this i hope it works i have tried

<input id="Radio1" type="radio"  önclick="return alert('Hi friends i m sachin here');" />

Radio buttons are closely related to check boxes. Only, with a radio button you get just the one choice from a list of options. With a check box you can tick all the boxes, if you wanted.

<Input type = radio Name = r1 Value = "NE">North East
<Input type = radio Name = r1 Value = "NW">North West
<Input type = radio Name = r1 Value = "SE">South East
<Input type = radio Name = r1 Value = "SW">South West
<Input type = radio Name = r1 Value = "midlands">Midlands

You can play with radio buttons using javascript as belows.

function GetSelectedItem() {
chosen = ""
len = document.f1.r1.length
for (i = 0; i <len; i++) {
if (document.f1.r1[i].checked) {
chosen = document.f1.r1[i].value
}
}
if (chosen == "") {
alert("No Location Chosen")
}
else {
alert(chosen)
}
}

Use Javascript to check whether the Radiobutton is selected or not:

<script type="text/javascript">
    function as()
    {
        //Get the client ID of the control
        var tableID = '<%= RadioBtn.ClientID %>';
        var radioButtons = document.getElementsByName(tableID)
        var totalRows = radioButtons.length;
        var radioButton;
        var flagRadioButtonChecked = false;
        for(var rowIndex=0; rowIndex< totalRows; rowIndex++)
        {
            radioButton = radioButtons[rowIndex]
            //Check if it's a radio button
            if(radioButton.type == 'radio')
            {
                //Check if it's checked
                if(radioButton.checked)
                {
                    //current radio button is checked
                    flagRadioButtonChecked=true;
                    //breaking from here will keep reference of checked radio button to radioButton variable
                    break;
                }
            }
        }
        //Check if any radio button is checked
        if(flagRadioButtonChecked)
        {
            alert(radioButton.value + ' is checked...');
        }
    }
    </script>

Hope this will solve your problem.

function radiobuttonchecking( ) {
          var tableID ='<%= RadioBtn.ClientID %>';

          var radioButtons = $(tableID).find(':input')
          var totalRows = radioButtons.length;
          var radioButton;
          var flagRadioButtonChecked = false;
          for (var rowIndex = 0; rowIndex < totalRows; rowIndex++) {
              radioButton = radioButtons[rowIndex]
              //Check if it's a radio button
              if (radioButton.type == 'radio') {
                  //Check if it's checked
                  if (radioButton.checked) {
                      //current radio button is checked
                      flagRadioButtonChecked = true;
                      //breaking from here will keep reference of checked radio button to radioButton variable
                      break;
                  }
              }
          }

//Check if any radio button is checked
       if(flagRadioButtonChecked)
       {
           alert(radioButton.value + ' is checked...');
       }
   }
   </script>

its working in my application

<script type="text/javascript">
function as()
{
var checked = document.getElementById("RadioBtn").checked);
if(!checked){
alert("check the field");
}
</script>