Prevent Duplicate entry in Sql server DataBase using javascript

If you want to do it in the client side and not in the server side it is relatively simple to use AJAX from JQuery.

- You could make the 'Submit' button ('Accept' or whatever name you find appropiate) be disabled at page load.

- When the user changes the text in the input control you can detect the text changed event and use AJAX to (in the background) try to download one text/xml document from your site. You can use the text in the input control as part of the query.

- In the server side, when it receives the request for the file (you should of cource trap it as it will refer to non existing page/document) your code should check in the database for the presence or not of that text and return the appropiate content which may simply be one '1' or one '0'.

- On the handler for the event fired when the download has been completed (client side, captured in JQuery) you take that value and decide enabling/disabling the 'submit' button.


It is complex to put it all together but gives the impression of being all done client-side.

The simplest way to do it is with server side data validation.

This piece of code could help you:

Put something like this on the event handler:

LoadMyFile("myfiles/oneXmlFile.xml", function(xml) {
    // This variable contains the parsed xml;
    // ...do something with it here.
});

And make this function available for your page code. sourceDoc is the url and Ready the callback called when the filed download succeeds.

function LoadMyFile(sourceDoc, Ready) {
    $.ajax({
        type: "GET",
        url: sourceDoc,
        dataType: "xml",
        success: function(xml) {
            Ready(xml);
        }
    });
}

p.d. That's how i did something similar some time ago, but creating and testing some code for you could take too long now.