Stopping onclick from firing when onclientclick is false?

Question

Is it possible to use the onclientclick property of a button to do a clientside check. If the check returns true, then fire the onclick event. If the clientside check returns false, don't fire the onclick event.

Is that possible?

UPDATE:

These 2 work:

Stops the form from submitting:
OnClientClick="return false;"

---

Allows the form to submit:
OnClientClick="return true;"

---

The next 2 do not work:

// in js script tag
function mycheck() {
    return false;
}

// in asp:button tag
OnClientClick="return mycheck();"

---

// in js script tag
function mycheck() {
    return true;
}

// in asp:button tag
OnClientClick="return mycheck();"

It submits the form both times.

Why is that?

Answer 1

You want to add return inside OnClientClick after a function is called. Otherwise, the button will post back even if function returns false.

<asp:button ID="Button1" runat="server" OnClick="Button1_Click" 
    OnClientClick="return checkValidation()" Text="Submit" />

<script type="text/javascript">
    function checkValidation() {
        return confirm('Everything ok?');
    }
</script>

Answer 2

Sure. If you use return false within your OnClientClick it will prevent any navigation from happening. So you're code would look like:

<asp:LinkButton runat="server" OnClientClick="if(!ValidatePage()) { return false;}" />

Answer 3

Yes you can, In onclientClick function call use preventDefault()

function onclientClickFun(e)
{
  if(!IsValidationSuccess)
 {
   e.preventDefault();
 }

}

OR

function onclientClickFun(e)
{
  if(!IsValidationSuccess)
 {
   return false;
 }

}

Answer 4

I came across this issue too. Did not like to have to put the OnClientClick=return false on every linkbutton. With a simple page it just easier to use an anchor and avoid asp filling the href in for you.

However this is not always possible. So a Simple conclusion is just to inherit the LinkButton and add a variable like AutoPostBack. if false then just override the output with the html or add the OnClientClick in. I dont really like inline tags.

namespace My.WebControls {
    [ToolboxData("<{0}:LinkButton runat=server ID=btn></{0}:LinkButton>"), ParseChildren(true), ToolboxItem(true)]
    public class LinkButton : System.Web.UI.WebControls.LinkButton {

         private bool _postback = true;
         [Bindable(true), Category("Behavior"), DefaultValue(true), Description("Gets or Sets the postback click behavior")]
         public bool AutoPostBack { get { return _postback; } set { _postback = value; } }


         protected override void Render(System.Web.UI.HtmlTextWriter writer) {
             if(!AutoPostBack){
                 this.OnClientClick = "return false";
             }
             base.Render(writer);
         }
    }
}

Many attributes should need to be handled in a ViewState but in this case I think we are good;

Answer 5

In the server page create the button:

var button1 = new Button();  
button1.ServerClick += new EventHandler(button1_ServerClick);
button1.OnClientClick = SetJsForSaveBtn();
button1.Attributes.Add("UseSubmitBehavior", "false");
panel.Controls.Add(button1 );

//Contains the server code

private void saveBtn_ServerClick(object sender, EventArgs e)
{
   //do something if ClientClick returns true
}

//Contains the JS code for the page

LiteralControl js = new LiteralControl();
panel.Controls.Add(js);
js.Text =@"<script type='text/javascript'> 
$(document).ready(function(){
 function CheckValidationOnClient(){
   if(!ValidatePage()){
    return false;
   }
   else{
    return true;
   }
 };
});
</script>   ";

private string SetJsForSaveBtn()
{
  var jsfunc = @" return CheckValidationOnClient()";
  return jsfunc ;
}