'宣言 Public Property CenterOfStartCircle As System.Nullable(Of PointF)
public System.Nullable<PointF> CenterOfStartCircle {get; set;}
(0, 0) is the top-left corner, (1, 1) is the bottom-right corner.
If not specified, the center of the start circle coincides with CenterOfEndCircle.
'宣言 Public Property CenterOfStartCircle As System.Nullable(Of PointF)
public System.Nullable<PointF> CenterOfStartCircle {get; set;}