[Value] DT_PREFIXONLY [Meaning] 
Draws only an underline at the position of the character following the ampersand (&) prefix character. Does not draw any other characters in the string. For example, Example: input string: "A&bc&&d"n normal: "Abc&d" DT_PREFIXONLY: " _ " Compare with DT_HIDEPREFIX and DT_NOPREFIX.