Visual Basic

If sender is textbox1 then 
'Modify context menu here
End If

If sender.gettype is gettype(textbox) then
'Modify context menu here
End If

dim ctrl as control = trycast(sender,control)
If ctrl isnot nothing andalso ctrl.name = "textbox1" then
'Modify context menu here
end if

Private Sub ContextMenuStrip1_Opening(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles ContextMenuStrip1.Opening
    Dim source As Control = ContextMenuStrip1.SourceControl

    'Example: Test it's name
    If source.Name = "Textbox1" Then

    End If

    'Example: Test if it's a specific control
    If source Is TextBox1 Then

    End If

    'Example: Test if it's a type of control
    If source.GetType Is GetType(TextBox) Then

    End If
End Sub

Private Sub Add_text_to_report(ByVal The_text As String, ByVal Style As System.Drawing.FontStyle, ByVal Colour As System.Drawing.Color)
        Dim Font As New Font(rtBox.Font.FontFamily, rtBox.Font.Size, Style)
        Dim Len As Integer = rtBox.Text.Length()

        ' Add the text
        rtBox.AppendText(The_text)

        ' Now format it as specified
        rtBox.SelectionStart = Len
        rtBox.SelectionLength = The_text.Length
        rtBox.SelectionFont = Font
        rtBox.SelectionColor = Colour

        ' Clear the selection
        rtBox.SelectionStart = 0
    End Sub