how to detect if the text box has focus ?

put the onFocus attribute inside the TextBox and run Js when onFocus triggeres.

i.e.

TempTextBox.Attributes.Add("onFocus", "DoFocus(this);");

Now the put the Js for DoFocus

function DoFocus(this)
{

}

Now object this is your TextBox object now play with it as you want.

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