User text input handling using TextBox

Question

I have this control:

enter image description here

I'm trying to create a kind of validation, that whenever the user enters text to the TextBox, the "Add" button will be Enabled, and when the text is "" (null), the "Add" button is disabled. I dont want to use validators.

here's the code:

protected void addNewCategoryTB_TextChanged(object sender, EventArgs e)
    {
        if (addNewCategoryTB.Text != "")
            addNewCategoryBtn.Enabled = true;
        else
            addNewCategoryBtn.Enabled = false;
    }

The problam is, that when the user enter's text, the "Add" button doesn't changes from disabled to enabled (and vice versa)...

any ideas?

RMalke · Accepted Answer · 2013-05-17 20:38:40Z

6

Is it Web Forms? In Web Forms the TextChanged event of the TextBox won't fire by default. In order to fire the event, you have to set the AutoPostBack property of the TextBox to true.

BUT, this would perform a HTTP post, what is kink of ugly, or you can wrap that in an UpdatePanel

A more elegant option, is to do that using jQuery, to do that in jQuery, you'll need some code like:

$(document).ready(function() {
    $("#<%= yourTextBox.ClientID %>").change(function() {
        var yourButton = $("#<%= yourButton.ClientID %>")

        yourButton.attr('disabled','disabled');
        yourButton.keyup(function() {
            if($(this).val() != '') {
                yourButton.removeAttr('disabled');
            }
        });

    });
});

edited May 17, 2013 at 20:38

answered May 17, 2013 at 20:28

RMalke

4,12432 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Bearcat9425 Over a year ago

$("#<%= aspControl.ClientID %>") asp.net runs server side and creates a clientID for that control, Jquery needs the clientID in order to access the correct control it wont do it simply by control Name.

omi Over a year ago

thank you. actually, I dont want to use jQuery, so Ill think of different way to validate it...THANKS!

qJake Over a year ago

@omi Why wouldn't you want to use jQuery? There are very few reasons not to use it in today's day and age.

qJake Over a year ago

jQuery adds to, and simplifies most of the common Javascript functions and makes your code a lot easier to read and maintain, not to mention it has awesome documentation that you can learn from. I highly suggest you take the time to learn it, it will save you time in the end.

qJake · Accepted Answer · 2013-05-17 20:26:40Z

4

You'll need to accomplish this with Javascript, since ASP.NET is incapable of performing such client-side modifications. Think about it ... every time you pressed a letter inside the text box, it would have to postback and refresh the page in order to determine if the text box was empty or not. This is one way that ASP.NET differs from Winforms/WPF.

answered May 17, 2013 at 20:26

qJake

17.2k17 gold badges88 silver badges138 bronze badges

1 Comment

omi Over a year ago

great answer! my background is actually winforms, so I needed this tip!

Community · Accepted Answer · 2020-06-20 09:12:55Z

3

TextChanged events will make postback on server every time. You don't need to increase those request for such task.

You can use jquery to achieve this

var myButton = $("#btnSubmit");
var myInput=$("#name");
myButton.prop("disabled", "disabled");

myInput.change(function () {
  if(myInput.val().length > 0) {
    myButton.prop("disabled", "");
  } else {
    myButton.prop("disabled", "disabled");
  }
});

JS Fiddle Demo

You just need to take care of elements Id when you are using Server Controls. For that Either you can use ClientID or set property ClientIdMode="Static"

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered May 17, 2013 at 20:29

Sachin

41.1k7 gold badges94 silver badges107 bronze badges

Collectives™ on Stack Overflow

User text input handling using TextBox

3 Answers 3

4 Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related