C＃如何使实例化更抽象？

Question

I am currently writing a VSTO for Excel but this would apply to other applications, too. The app is for a number of sites, so I am writing core logic and site-specific logic. I am trying to keep all site-specific logic in a single subfolder to make it easier to exchange between sites.

VSTOs have a class called ThisAddIn.cs . It instantiates a class called AddInUtilities . Mine looks like this:

[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
public class AddInUtilities : IAddInUtilities
{
    public void ImportData()
    {
        var activeWorksheet = Globals.ThisAddIn.Application.ActiveSheet as Excel.Worksheet;
        if (activeWorksheet == null) return;

        var loadCsv = new CsvImporter();  
        if (loadCsv.IsNotCancelled) loadCsv.AndImportIndexDataInto(activeWorksheet);
    }
}

My CsvImporter class is site-specific. It is based on an abstract class, which in turn is based on an interface, which allowed me to move everything that is core logic in the importer away from the site-specific subfolder.

What I can't get my head around is how to make the instantiation of my class

var loadCsv = new CsvImporter();

abstract? I obviously cannot instantiate the interface or abstract class. I could move this class into the site-specific code, but then my ThisAddIn.cs , which refers to this class will need to refer to site-specific code (or at least use the namespace of that subfolder).

The only way around that, that I can think of, would be to move the files physically into the subfolder but leave the namespace as is. Is there a better way? I feel I am missing something.

Answer 1

I would recommend to make loadCsv a class property and push the needed object from the site specific code:

[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
public class AddInUtilities : IAddInUtilities
{
    ICsvImporter CsvImporter = null;

    public void ImportData()
    {
        var activeWorksheet = Globals.ThisAddIn.Application.ActiveSheet as Excel.Worksheet;
        if (activeWorksheet == null) return;

        if (CsvImporter != null && CsvImporter.IsNotCancelled) 
        {
             CsvImporter.AndImportIndexDataInto(activeWorksheet);
        }
    }
}

public class SiteSpecificClass
{
    public void SiteImportMethod()
    {
        var addinUtility = new AddInUtilities();
        addinUtility.CsvImporter = new CsvImporter();
        addinUtility.ImportData();
    }
}