How to set combobox text as permenant

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C#

i would like to set my combobox's text as permenant

for an example in the early stage
combobox text is set as "please select your option here"
if i have select any option in the combobox
i don't want my combobox's text to be update as the selected option in combobox

but whenever i click option in combobox, my combobox's text will be update as what i have selected in combobox

What I have tried:

private void comboBox1_TextChanged(object sender, EventArgs e)
        {
              comboBox1.text = "please select your option here" ;
        }

after i add this code, it still update the text of combobox to the selected option