CODEWITHSUNDEEP
c#linq
pennstatephil
pennstatephil

Reputation: 1643

Remove items from list using their IDs and linq

I have a List of "widget"s (which have an int ID), and a List of selected IDs. My end goal is to have a List of hydrated widgets that agrees with the ID list inside my "set".

public List<Widget> widgets { get; set; }

public List<int> widgetIds
{
    get
    {
        return widgets.Select(x => x.widgetId).ToList();
    }
    set
    {
        foreach (int addId in value.Except(widgets.Select(x => x.widgetId)))
        {
            widgets.Add(_dbWidgetHelper.getWidget(addId));
        }

        //I need to invert the add somehow
    }
}

I've been trying everything I can think of using RemoveAll and Except, but I can't wrap my head around the solution yet. I know this can be done in one line, but the closest I've got is:

var removeIds = widgets.Select(x => x.widgetId).Except(value);

//this is me trying anything I can think of... obviously a syntax error.
widgets.RemoveAll(x=>x.widgetId in removeIds);

Upvotes: 0

Views: 67

Answers (1)

JaredPar
JaredPar

Reputation: 754735

Try the following. Note that I changed removeIds to be a HashSet<int> to prevent the query from being re-evaluated every time and to make the look up faster

var removeIds = new HashSet<int>(widgets.Select(x => x.widgetId).Except(value));

widgets.RemoveAll(x => removeIds.Contains(x.widgetID));

Upvotes: 2

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