Add Javascript Keydown event from C# to a textbox

Question

I'm building a set of text boxes from asp.net repeater and trying to add a key down event from C# code to those text boxes to prevent user from entering a specific character (comma(,)). I can't use the text box id itself in Javascript because its built dynamically with diff id's. Now I have no idea how to pass the e object to the textbox's keydown event from C#.

Any suggestion is much appreciated.

Code Snippet :

 TextBox txtTextField = e.Item.FindControl("txtAns_1") as TextBox;
 txtTextField.Attributes.Add("keydown", "PreventChars(" + txtTextField +")");

Javascript

   function PreventChars(e) {

            var k = String.fromCharCode(e.which);

            if (k.match(/,/g))
            {
                e.preventDefault();
            }

        };

Prashanth Reddy · Accepted Answer · 2020-01-04 07:11:58Z

1

use ClientID

ClientID returns The control ID for HTML markup that is generated by ASP.NET.

Change Code Snippet to:

TextBox txtTextField = e.Item.FindControl("txtAns_1") as TextBox;
txtTextField.Attributes.Add("keydown", "PreventChars(" + txtTextField.ClientID +")");

answered Jan 4, 2020 at 7:11

Prashanth Reddy

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1 Comment

GreySage Over a year ago

To be honest, I don't exactly understand how passing the ClientID as an object works, but it does work. You need to dig a bit on the front-end to get the event argument but you can find it under e.keydown.arguments[0].key.

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