How do you programmatically apply a css class to an asp.net control?

Question

I\'m wondering how I can apply a CSS class to an ASP.NET Control (TextBox in this case) through the backend in C#. For example:

Answer 1

You can implement adding cssClass like

firstName.CssClass = "input left selected";

Or

make onClick event for textbox

Then in code-behind:

void firstName_Click(Object sender, EventArgs e) {
    MyTextBox.CssClass = "input left selected";
}