I'd like to click on a Text Box and delete the initial message, how can I achieve that?

Hello all
I've created a form and I in this form has an initial message, I would like that when I click on the TextBox, the initial message would be deleted
I've created that with a condition "If", but I think on the header is the problem
I just have experience with VBA
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Partial Class Ishikawa
Inherits System.Web.UI.Page
Protected Sub Materialtxt_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Materialtxt.????? (I don't know what type in this part)
If Materialtxt.Text = "Click to add information Then
Materialtxt.Text = ""
End If
End Sub
End Class
 
 
 
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