Display or conceal database fields in ASP.NET based on their null or not null values

I need help hiding a data field in ASP.NET when it is null. Here's what I have so far:

<script runat="server" type="text/vb">
// target the id called test
var test = document.getElementById("test");

// if test is not empty, show
// else hide test
if (test.value != null){
    document.getElementById("test").style.visibility = visible;
}else{
    document.getElementById("test").style.visibility = hidden;
}


<p><asp:Label runat="server" id="test"><%# Eval("DBField")%></asp:Label></p>

Can someone please guide me on this? I keep encountering errors no matter what I try. I feel like it should be more straightforward...any suggestions would be appreciated.

Thank you in advance,

javascriptasp.net

Answer №1

It's difficult to provide an answer without knowing the specific error you're encountering. One issue that stands out is not using the ClientId of the asp.net control. Consider making the following adjustment:

var test = document.getElementById("test");

Change it to:

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

Remember, the ID assigned to an asp.net control is not necessarily the one rendered. Check out this article for more information on this topic.

Answer №2

There could be a few potential issues at play:

If you are using a server control, the ASP.NET runtime may change its ID depending on its parent. When you view the page source, you might see an ID like "ctl00_main_test" or something similar. To address this issue, you need to follow these steps:

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

if (test.text !== null){
    test.style.visibility = 'visible';
}else{
    test.style.visibility = 'hidden';
}

Since "visibility" corresponds to a CSS style, make sure to use quotes around "visible" and "hidden."

Keep in mind that while getElementByID should work well for modern browsers, older browsers might have unreliable implementations. Consider using jQuery to simplify this code:

if ($('#<%=test.ClientID%>').text() !== '' && $('#<%=test.ClientID%>').text() !== null){
    $('#<%=test.ClientID%>').show();
}else{
    $('#<%=test.ClientID%>').hide();
}

Answer №3

To handle empty strings in JavaScript, you should test for them using the following code:

var test = document.getElementById("<%=test.ClientID%>");
if (test){
    test.style.visibility = (test.value == "" ? "hidden" : "visible");
}

UPDATE

I just realized that you are using databinding syntax, which suggests that this Label is within a grid or similar structure. You can try a different approach like this:

<asp:Label ID="test" runat="server" Visible='<%#(String.IsNullOrEmpty(Eval("DBField")) == false)%>'><%#Eval("DBField")</asp:Label>

Answer №4

I successfully concealed information using the code snippet below:

<asp:PlaceHolder ID="PlaceHolder" runat="server" Visible='<%# IIf((Eval("confidential")).ToString().Length > 0, "true", "false") %>'>
     <h3>confidential</h3>
     <asp:Label ID="confidential" runat="server" Text='<%# Bind("confidential") %>'></asp:Label>
</asp:PlaceHolder>

Answer №5

Span elements do not contain a value:

if ($('#<%=test.ClientID%>').html() != "") //Using jQuery

or 

if (document.getElementById("<%=test.ClientID%>").innerText != "")

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