How to add an additional css class from code behind using ASP.NET?

Question

CURRENT TEXTBOX

<asp:TextBox ID="txt" CssClass="MyClass" runat="Server" />

DESIRED OUTPUT

<asp:TextBox ID="txt" CssClass="MyClass Error" runat="Server" />

Testing

txt.CssClass = "Error"

This replaces current css class.

txt.CssClass = "MyClass Error"

This works but but is greatly inefficient having to specify class.

txt.Attributes.Add("class", "Error")

This only works if no initial class is set.

txt.Attributes("class") += " Error"

This does not work for me.

@mikey I also believe so, but am unable to test it right now. — emerson.marini
– emerson.marini, Commented Aug 6, 2014 at 13:15
@MelanciaUK yes same here ;) that is why I went with 'perhaps' — mikey
– mikey, Commented Aug 6, 2014 at 13:15
Give it to Rob W, the utility methods he's linked to are more robust. I imagine that one could become very frustrated dealing with the string concatenation and the helper methods help to prevent duplicates — mikey
– mikey, Commented Aug 6, 2014 at 13:20

DreamTeK · Accepted Answer · 2020-06-05 09:37:34Z

14

Add additional CssClass like this:

txt.CssClass = txt.CssClass + " Error"

The above can also be abbraviated as:

txt.CssClass += " Error"

answered Aug 6, 2014 at 13:20

DreamTeK

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Comments

Community · Accepted Answer · 2017-05-23 12:09:17Z

3

I know that you were looking for a quick one-liner. However, this previous answer may prove useful going forward:

CommunityBot

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answered Aug 6, 2014 at 13:16

Rob W.

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