Detect if Asp.Net form is valid with javascript/jquery

I have a form which is in an updatePanel and I have a span with hidden loading image, which I want to show when user clicks to submit button but I first need to check if page is valid on client side. Also I'm making loading span visible with jQuery. Here is my code:

<html>
<head>
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js" type="text/javascript"></script>
    <script type="text/javascript">
    function showLoading() {
        $('#loader').show();
    }
    </script>
</head>

<body>
<asp:ScriptManager ID="smMain" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="upForm" runat="server">
<ContentTemplate>
    <asp:MultiView ID="mvContact" runat="server" ActiveViewIndex="0">
        <asp:View ID="vDefault" runat="server">
            <asp:TextBox ID="tEMail" runat="server" CssClass="input" />
            <asp:RequiredFieldValidator ID="rfvEMail" runat="server" ControlToValidate="tEMail" ErrorMessage="* required" Display="Dynamic" />
            <asp:RegularExpressionValidator ID="revEMail" runat="server" ControlToValidate="tEMail" ErrorMessage="* invalid" Display="Dynamic" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*" />
            <asp:ImageButton ID="btnSubmit" runat="server" ImageUrl="~/Assets/Images/btnSubmit.png" ToolTip="Submit Form" style="margin:5px 5px 0 -5px" onclick="btnSubmit_Click" OnClientClick="showLoading();" />
            <span id="loader"><img src="Assets/Images/loader.gif" title="Sending..." /></span>
        </asp:View>
        <asp:View ID="vResult" runat="server">
            <div class="result">
                <span id="lResult" runat="server">Your message is sent</span>
            </div>
        </asp:View>
    </asp:MultiView>
</ContentTemplate>
</asp:UpdatePanel>
</body></html>

Okay I found a solution. Page_ClientValidate() does the trick.

function showLoading() {
    if (Page_ClientValidate()) { $("#loader").show(); }
        else { alert("Form is invalid!"); }
    }

I think it would be better to use the property Page_IsValid instead of the method Page_ClientValidate().

function showLoading() {
if (Page_IsValid) { $("#loader").show(); }
    else { alert("Form is invalid!"); }
}

If you don't want to call Page_ClientValidate() you can use Page_IsValid but set a timeout so that the validation occurs first.

OnClientClick="javascript:setTimeout(function() { if (Page_IsValid) document.getElementById('preloader').style.display='block';}, 1000);"

the preloader is hidden in the middle

<img src="/images/preloader.gif" id="preloader" style="display:none; position: fixed; top: 50%; left: 50%; margin-top: -50px; margin-left: -100px;" />

Thank you Hasan, you made my day :)

I want to share some bit of my problem and resolution. I have an ASP.NEt page using a MasterPage. When submiting a form I used the fadeOut effect to hide the buttons. However if the form is not completed the buttons was gone. I simply add a condition on hasan suggestion to the OP problem. Here is my final code.

//Fade out buttons when clicked but only if page validate
$('.button').click(function () {
    if (Page_ClientValidate()) { $('.button').fadeOut('slow'); }
});//End of Fade out buttons

Thanks again Hasan :)

来源：https://stackoverflow.com/questions/2543179/detect-if-asp-net-form-is-valid-with-javascript-jquery

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jquery

ASP.NET

validation

asp.net-ajax