返回记录为true或全部的方法

Question

Is there a better way to write the method below? I want to return content based on a bool variable IsPublished .

When IsPublished is null I want to return entries that are both true and false .

public IList<Content> GetContent(bool? IsPublished)
{
    if (IsPublished != null)
    {
        return _UoW.Content.All.Where(c => c.IsPublished == IsPublished).ToList();
    }
    else
    {
        return _UoW.Content.All.ToList();
    }
}

Answer 1

If by better, you mean shorter, operator ? can be the solution. Also, there is no point using filter when the isPublished == null . Please refer to Microsoft Documentation here for ? operator.

public IList<Content> GetContent(bool? IsPublished)
{
    return isPublished != null ? _UoW.Content.All.Where(c=>c.IsPublished== IsPublished).ToList() : _UoW.Content.All.ToList();
}

Answer 2

This is not as efficient, but is compact:

public IList<Content> GetContent(bool? IsPublished)
    => _UoW.Content.All.Where(c => !IsPublished.HasValue || c.IsPublished == IsPublished).ToList();

Answer 3

You can use the null coalesce operator ?? and filter on x.IsPublished == (v ?? x.IsPublished)

public class A
{
    public int Id { get; set; }
    public Nullable<bool> IsPublished { get; set; }
}

public static IEnumerable<A> Filter(IEnumerable<A> items, Nullable<bool> v)
{
    return items.Where(x => x.IsPublished == (v ?? x.IsPublished)).ToList();
}

var listy = new List<A>();
listy.Add(new A() { Id=1, IsPublished=null });
listy.Add(new A() { Id=2, IsPublished=true });
listy.Add(new A() { Id=3, IsPublished=false });
listy.Add(new A() { Id=4, IsPublished=null });
listy.Add(new A() { Id=5, IsPublished=true });
listy.Add(new A() { Id=6, IsPublished=false });

C# interactive console demo:

> Filter(listy, null)
List<Submission#0.A>(6) { Submission#0.A { Id=1, IsPublished=null }, Submission#0.A { Id=2, IsPublished=true }, Submission#0.A { Id=3, IsPublished=false }, Submission#0.A { Id=4, IsPublished=null }, Submission#0.A { Id=5, IsPublished=true }, Submission#0.A { Id=6, IsPublished=false } }
> Filter(listy, true)
List<Submission#0.A>(2) { Submission#0.A { Id=2, IsPublished=true }, Submission#0.A { Id=5, IsPublished=true } }
> Filter(listy, false)
List<Submission#0.A>(2) { Submission#0.A { Id=3, IsPublished=false }, Submission#0.A { Id=6, IsPublished=false } }  

(The class above is A instead of Content and the method is Filter instead of GetContent )

Answer 4

If you are trying to be brief, you don't need { } blocks for single statement if else bodies.

But perhaps a single return point is what you are looking for:

public IList<Content> GetContent(bool? IsPublished) {
    var ans = _UoW.Content.All;
    if (IsPublished.HasValue)
        ans = ans.Where(c => c.IsPublished == IsPublished);

    return ans.ToList();
}

(Assuming the type of All is compatible with the return type of Where . If not, you can change the assignment to be var ans = _UoW.Content.All.Where(c => true) .)