The elements in the dash_pattern array set the length of each dash and space in the dash pattern. The first element sets the length of a dash, the second element sets the length of a space, the third element sets the length of a dash, and so on. Consequently, each element should be a non-zero positive number.
The length of each dash and space in the dash pattern is the product of the element value in the array and the width of the xtd::drawing::pen.