Why should you care?

ShopNest “import catalog” always validate → transform → save, but CSV vs Excel differ in parse details.

See it live — copy this example

Paste into a C# console or class library project and run dotnet run.

public abstract class CatalogImport
{
    public void Run(string path)
    {
        var rows = Parse(path);
        rows = Transform(rows);
        Save(rows);
    }
    protected abstract List<string> Parse(string path);
    protected virtual List<string> Transform(List<string> rows) => rows;
    protected abstract void Save(List<string> rows);
}
public sealed class CsvCatalogImport : CatalogImport
{
    protected override List<string> Parse(string path) => new() { "HD-100", "HD-200" };
    protected override void Save(List<string> rows) => Console.WriteLine($"saved {rows.Count}");
}

new CsvCatalogImport().Run("a.csv");

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• Run is the template.
• CsvCatalogImport fills Parse/Save.
• Transform has a default.
• Prefer composition if inheritance gets awkward.

Practice next

1. Run CSV import.
2. Add ExcelCatalogImport.
3. Override Transform to uppercase SKUs.
4. Add a BeforeSave hook.
5. Log each step in Run.

Remember

Fixed algorithm steps. Override hooks. Shared sequence.

ShopNest catalog import

CSV/Excel importers share validate→save flow.

Outcome: New formats override parse only.