Can't read value from textbox into javascript variable

Question

Hello I am trying to read a textbox(runatserver) after is gets populated form the server into a javascript variable,but it gives me a console error that "can't read form NULL" however the text box is populated by the string I want to read

this is my text box:

 <form runat="server">

        <asp:TextBox ID="ServerSideTextBox" runat="server" />
    </form>

This is how I am populating it in C#:

ServerSideTextBox.Text= Object_JSON_Class.JSON_DataTable(dt);

it gets the right data also shows the right data string but the PROBLEM is when I try to read the value of the text box like this:

 var oServerSideTextBox= document.getElementById("ServerSideTextBox"); 
var oServerJSON_String=eval("("+oServerSideTextBox.value+")");

I get a console error that I can't read form NULL,but the text box does have the string I want to read into javascript variable,please help

Habib · Accepted Answer · 2012-04-13 07:03:53Z

1

 var txtToIncr = document.getElementById('<%=ServerSideTextBox.ClientID%>')

Check out this link, about reading ASP.Net controls through javascript

edited Apr 13, 2012 at 7:03

answered Apr 13, 2012 at 6:51

Habib

224k30 gold badges420 silver badges446 bronze badges

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

8 Comments

Habib Over a year ago

check your generated HTML and see what is being rendered against serversidetextbox id

Snedden27 Over a year ago

I saw that too the id is the same i.e serversidetextbox (ignoring caps)

Habib Over a year ago

try var t = document.forms[0]['ServerSideTextBox'].value; and see if it gets the value

Snedden27 Over a year ago

nope ain't working,I have also read the link you have given me,according to it .ClientID should solve the problem but its not,maybe its because of something else then ID mismatch,can't figure out where I am going wrong tho

mslliviu Over a year ago

In that case, are you sure that the error is generated by the piece of code: var oServerSideTextBox= document.getElem....; Maybe you have an error on previous lines of javascript

|

npinti · Accepted Answer · 2012-04-13 06:52:05Z

1

Try this:

var oServerSideTextBox= document.getElementById("<%=ServerSideTextBox.ClientID%>");

If that does not work, try something like this:

var oServerSideTextBox= document.getElementById("<%=ServerSideTextBox.ClientID%>_text");

Components are assigned different ID's when rendered by the client's browser. You can take a look here for more information.

answered Apr 13, 2012 at 6:52

npinti

52.2k5 gold badges74 silver badges98 bronze badges

Comments

mslliviu · Accepted Answer · 2012-04-13 06:52:12Z

0

put this on yout textbox ClientIDMode="Static"

answered Apr 13, 2012 at 6:52

mslliviu

1,1383 gold badges12 silver badges30 bronze badges

Comments

Priyank Patel · Accepted Answer · 2012-04-13 07:27:21Z

0

Your server textbox's ID will be different if you use it in a master page structure , try finding its id.Because its actual id might be something like this ctl00_ContentPlaceHolder1_ServerSideTextbox.Check that.

Assign a class to yout textbox then try this to find the id.

$('.textbox').on('blur', function() {

        var error = this.id;
        alert(error);
                                       )};

edited Apr 13, 2012 at 7:27

answered Apr 13, 2012 at 7:03

Priyank Patel

7,01611 gold badges62 silver badges88 bronze badges

5 Comments

Snedden27 Over a year ago

I am not using master page structure right now, and how do I find the actual id the text box?

Priyank Patel Over a year ago

@Snedden27 , did you try that

Snedden27 Over a year ago

hmm its laughable but the ID in the pop-up is same ie ServerSideTextBox ,

Priyank Patel Over a year ago

@Snedden27 , strange I ran into similar problem sometime ago , my issue was the id.

Priyank Patel Over a year ago

@Snedden27 , did you check this in other browsers also

riffnl · Accepted Answer · 2012-04-13 09:46:00Z

0

Reading the comments. I think you're referring to the wrong textbox-ID.. So I made a small test-thingy: this should work.. If not look into the source from your HTML - there you can see the ID.

<script type='text/javascript'>
    function testvalue() {
        var oServerSideTextBox = document.getElementById('<%=ServerSideTextBox.ClientID%>');
        if (oServerSideTextBox == null) {
            alert('this is null');
        }
        else {
            alert(oServerSideTextBox.value);
        }
    }
</script>



<body>
    <form id="form1" runat="server">
    <div>
        <asp:TextBox ID="ServerSideTextBox" runat="server" Text="Testvalue" />
        <input type='button' onclick='testvalue();' value='Click' />
    </div>
    </form>
</body>

edited Apr 13, 2012 at 9:46

answered Apr 13, 2012 at 7:41

riffnl

3,1911 gold badge21 silver badges33 bronze badges

Collectives™ on Stack Overflow

Can't read value from textbox into javascript variable

5 Answers 5

8 Comments

Comments

Comments

5 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

8 Comments

Comments

Comments

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related