Custom validator fires but does not prevent postback

问题

I've seen a lot of questions about this already, but I'm stumped! Please help!

I have a customvalidator. It's firing but it's not preventing postback. Please help me in doing so! I can see that console.log registers before the post. But, it posts back anyway. How do I prevent the postback?

I've tried adding a control to validate, and validate empty text equal to true. I also tried adding e.preventdefault, which did not work :(

How can I prevent the postback?

    <script type="text/javascript">
//<![CDATA[
function validateWhyUnlikely(source, args) {
    console.log(1);
    args.isValid = false;
}
//]]>

<asp:TextBox ID="txtWhyUnlikely" runat="server" Rows="4" cols="20"
            CssClass="surveyTextArea" />
<asp:CustomValidator runat="server" ID="cfvWhyUnlikley" ErrorMessage="Please provide a reason since you rated an item as unlikely to provide."
        CssClass="surveyError surveySmallIndent" Display="Dynamic" 
        ClientValidationFunction="validateWhyUnlikely" />
<asp:Button ID="btnSubmit" runat="server" Text="Submit" CssClass="smallSpecial" OnClick="btnSubmit_Click" />


jQuery(document).ready(function () {
    jQuery('#<%= btnSubmit.ClientID %>').click(function (e) {
        if (Page.IsValid == false) {
            console.log(false);
            e.preventDefault();
            return false;
        }
    });
});

回答1:

Everything looks ok althought I am not sure why you are attaching the Click function to your submit button. I would remove that and test it as it maybe be overriding the default behavior.

Also I think you need to capitalize the IsValid property:

args.IsValid = false;

回答2:

I too faced this issue, I was trying to add a custom validator to a dropdownlist which had a selectedIndexChange event attached to it. After i gave incorrect value for dropdown, i was able to se ethe error message i gave in Custom Validator but immediately after it Postback was happening.

However on adding this property CausesValidation="true" to the dropdownlist control resolved my issue.

Postback wasn't happening on incorrect value after adding this property to my dropdown.

回答3:

If it helps other people, I had a Validation group that I forgot to add the button to.

Make sure to add the button, the textbox and the validator to the same validation group for the postback to be prevented.

回答4:

I experienced this problem as well.

What I did was, in the C# procedure that was called by the button, at the top I added

if (IsValid == false)
         return;

I could not stop it performing the postback so this seemed to me like the only solution.

回答5:

You are misssing ControlToValidate="txtWhyUnlikely"

回答6:

Posting this as it might help someone that is getting the same weird behavior.

Initially I had the same issue as this post title. I checked all the suggestions here but my code seemed to be fine.

To fix this I replaced my cause validation control <asp:Button.. with a <button.. . Not sure why this is happening but happy it's working now.

hth

回答7:

<button tags are missing the correct javascript code to validate. <asp:Button does have the correct javascript rendered.

I've added this to any button tags:

btn.Attributes("onclick") = StringFmt("if(!Page_ClientValidate(''))return false;")

and that solved the post-back issue. No post-back occurs if the client-side detects an issue.

回答8:

I solved this problem by creating a variable:

 Boolean fieldIsValid = true;

and at the custom validating expression I would change the value if arguments weren't true:

if(args.IsValid == false)
            {
                fieldIsValid = false;
            }
            else
            {
                fieldIsValid = true;
            }

Then, I also put that in the submit click method:

protected void submit_Click(object sender, EventArgs e)
        {
            if (fieldIsValid)
            {
                //submit my things
            }
        }

来源：https://stackoverflow.com/questions/8170319/custom-validator-fires-but-does-not-prevent-postback