I am using aspx. If I have HTML as follows:
<div id="classMe"></div>
I am hoping to dynamically add a css class through the code behind file, ie on Page_Load. Is it possible?
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7 Answers
If you want to add attributes, including the class, you need to set runat="server" on the tag.
<div id="classMe" runat="server"></div>
Then in the code-behind:
classMe.Attributes.Add("class", "some-class")
7 Comments
DanDan
Thanks, I was sure it would be this simple.
Chris Haas
@Tyler, no. This adds a new class name to the control. You can also use
Clear and Remove on the Attributes collection. msdn.microsoft.com/en-US/library/…
jaminto
I'm not sure if i'm missing something, but if you have a class on the initial div (eg.
<div id="classMe" runat="server" class="original"></div>, the original class declaration is wiped out and you're left with just class="some-class" using the code above....seems to contradict @chris-haas's last commentjaminto
if you want to preserve existing classes, you need to do something like:
classMe.Attributes.Add("class", classMe.Attributes["class"] + " some-class" to not overwrite what you already have
styfle
@DevDave This does override existing classes because you are changing the entire class attribute. This is the same as setAttribute in javascript. "Adds a new attribute or changes the value of an existing attribute"
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If you're not using the id for anything other than code-behind reference (since .net mangles the ids), you could use a panel control and reference it in your codebehind:
<asp:panel runat="server" id="classMe"></asp:panel>
classMe.cssClass = "someClass"
Comments
Assuming your div has some CSS classes already...
<div id="classMe" CssClass="first"></div>
The following won't replace existing definitions:
ClassMe.CssClass += " second";
And if you are not sure until the very last moment...
string classes = ClassMe.CssClass;
ClassMe.CssClass += (classes == "") ? "second" : " second";
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BtnAdd.CssClass = "BtnCss";
BtnCss should be present in your Css File.
(reference of that Css File name should be added to the aspx if needed)
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controlName.CssClass="CSS Class Name";
working example follows below
txtBank.CssClass = "csError";
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Syntax:
controlName.CssClass="CSS Class Name";
Example:
txtBank.CssClass = "csError";
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If you want to retain the existing class, this would work:
string existingClass = classMe.Attributes["class"];
classMe.CssClass = existingClass + " some-class";
