onkeypress无法与asp.net Webform中的文本框一起使用

Question

onkeypress is not working with textbox in asp.net webform I want to prevent special characters and alphabets

Following is the aspx

<wijmo:C1InputText ID="SAC" runat="server" Style="width: 150px; display: inline-block;" onkeydown="return onlyNumbers(this,event);">
</wijmo:C1InputText>

function onlyNumbers(txt, event) {
    var charCode = (event.which) ? event.which : event.keyCode
    if (charCode == 46) {
        if (txt.value.indexOf(".") < 0)
            return true;
        else
            return false;
    }
       var regex = new RegExp("^[a-zA-Z0-9]+$");
    var key = String.fromCharCode(!event.charCode ? event.which : event.charCode);
    if (!regex.test(key)) {
       event.preventDefault();
       return false;
    }        
    if (charCode > 31 && (charCode < 48 || charCode > 57) && charCode!=190)
        return false;
    return true;
}

It returns false but not preventing to enter. If I replaced onkeypress with onkeydown it works

Answer 1

Please have a look on this post :

https://forums.asp.net/t/1888076.aspx?onKeyPress+vs+OnKeyDown+vs+OnKeyUp

this is the part of the answer you want :

OnKeyDown allows you to fire an event prior to the character being entered within the Textbox, so that you could check what the character being pressed is prior to determining if it should be allowed or not.

OnKeyUp will allow you to essentially hold a key down and will not fire an event until the key is released.

OnKeyPress will fire an event for each character key that is pressed (including those being held down).