How to make a reference to a struct in C#

in my application I have a LineShape control and a custom control (essentially a PictureBox with Label).

I want the LineShape to change one of its points coordinates, according to location of the custom control.

I had an idea to set a reference to a LineShape point inside the custom control and add location change event handler that chan开发者_如何学编程ges referenced point coordinates.

However built in Point is a struct which is a value type, so that won't work. Does anyone have idea, how to make a reference to a structure or maybe someone knows a workaround for my problem?

I tried the solution regarding usage of the nullable type but it still doesn't work. Here's the way I define the field in my custom control (DeviceControl):

private Point? mConnectionPoint;

And implementation of the location change event handler:

private void DeviceControl_LocationChanged(object sender, EventArgs e)
{
    if (mConnectionPoint != null)
    {
        DeviceControl control = (DeviceControl)sender;

        Point centerPoint= new Point();
        centerPoint.X = control.Location.X + control.Width / 2;
        centerPoint.Y = control.Location.Y + control.Height / 2;

        mConnectionPoint = centerPoint;
    }
}

You can pass value types by reference by adding 'ref' before it when passing in a method.

like this:

void method(ref MyStruct param)
{
}

Your method does not really require 'reference' access to the mConnectionPoint member; You can assign the location values directly to the referenced Point, as a member of your class:

private void DeviceControl_LocationChanged(object sender, EventArgs e)
{
    if (mConnectionPoint != null)
    {
        DeviceControl control = (DeviceControl)sender;

        mConnectionPoint.X = control.Location.X + control.Width / 2;
        mConnectionPoint.Y = control.Location.Y + control.Height / 2;
    }
}

However, if the reason for this code is to move the LineShape control, then you should go straight to the source. The best way to change the properties of a control is just to change the properties on the control:

    DeviceControl control = (DeviceControl)sender;

    line1.StartPoint = [calculate point1 coordinates];
    line1.EndPoint = [calculate point2 coordinates];