c＃使用未分配的局部变量OR对象实例未设置为引用？

Question

The following is a piece of code that does not seem to be working in c# even though it seems acceptable in c++. C# seems to have different standards for object instantiation.

                IList<PointF> vertices = null;

                float radius = (int)(bitmap.Width/3);

                for (double theta = 0; theta < 2 * 3.14; theta += 0.1)
                {
                    PointF temp = new PointF();
                    temp.X = centre.X + radius*((float)(Math.Cos(theta)));
                    temp.Y = centre.Y + radius*((float)(Math.Sin(theta)));
                    vertices.Add(temp);
                }

Where IList is an interface, and PointF is a struct. Tbh I do not know the differences when implementing interfaces vs classes.

If I do not assign "null" to vertices the code does not compile. However, if I do assign null then at runtime I get an error "object instance not set to a reference of an object" (because vertices is declared as null). How can I get around this error?

Answer 1

您必须实例化列表实例：

IList<PointF> vertices = new List<PointF>();

Answer 2

尝试为实现IList<PointF>顶点创建一个实例，例如：

IList<PointF> vertices = new List<PointF>();