I am having trouble understanding how to initialize a List of objects and use it with methods inside of a class. I understand the mechanics of the List, but not how to initialize it inside a method and use it later.

For example, I want to have a class that creates the List when it is constructed. Then, I want to use a method of that class to add elements to the list. The elements in the list are objects defined by the SolidWorks API.

So, to construct the List, I used...

public class ExportPoints : Exporter
{
    public List<SldWorks.SketchPoint> listOfSketchPoints;

    public ExportPoints(SldWorks.SldWorks swApp, string nameSuffix) :
        base(swApp, nameSuffix)
    {
        List<SldWorks.SketchPoint> listOfSketchPoints  = new List<SldWorks.SketchPoint>();
    }

    public void createListOfFreePoints()
    {
        try
        {
            [imagine more code here]
            this.listOfSketchPoints.Add(pointTest);

        }
        catch (Exception e)
        {
            Debug.Print(e.ToString());
            return;
        }
    }

This fails during execution as if the listOfSketchPoints was never initialized as a List.

So, I tried a hack and this worked:

    public ExportPoints(SldWorks.SldWorks swApp, string nameSuffix) :
        base(swApp, nameSuffix)
    {
        List<SldWorks.SketchPoint> listOfSketchPoints = new List<SldWorks.SketchPoint>();
        this.listOfSketchPoints = listOfSketchPoints;
    }

This approach creates the behavior that I want. However, it seems that I lack some understanding as to why this is necessary.

• Shouldn't it be possible to "initialize" a List that is a property of your object with a constructor?
• Why would you need to create the list, then assign the pointer of that new List to your property?