QQ: Group by poco not working

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Hi,

I have an array of Products, a custom POCO. Some of these products refer to the same item. Some will have the TariffUnrestricted price and another will have the StandingChargePenceDay . I need to merge these together.

I am trying to group the products together, then select out the key and the values for each product. I think the code will explain better:

C#

public override Product[] Import(string path, Func<Worksheet, bool> worksheetSelector = null)
{
    Product[] products = base.Import(path, worksheetSelector);

    var groups = products.GroupBy(p => new Product
    {
        PlanName = p.PlanName,
        RateType = p.RateType,
        ContractDuration = p.ContractDuration,
        Duration = p.Duration,
        TariffDescription = p.TariffDescription,
        //TariffUnrestricted = p.TariffUnrestricted,
        //StandingChargePenceDay = p.StandingChargePenceDay
    });

    products = groups.Select(g =>
    {
        Product product = g.Key;
        product.TariffUnrestricted = g.Max(p => p.TariffUnrestricted);
        product.StandingChargePenceDay = g.Max(p => p.StandingChargePenceDay);
        return product;
    }).ToArray();

    return products;
}

The items do not merge. The number of groups is always the same as the number of products (1:1).

I tried making the Product IComparable<Product>, IComparer<Product>, IEquatable<Product> but nothing works?

My google-fu is week. I cannot find the correct terms :C

What am I doing wrong?

Thanks
Andy

Posted 7-Jan-16 6:02am

Andy Lanng

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OriginalGriff · Accepted Answer · 2016-01-07T06:16:00

Why are you trying to group by a new product? All that will do is attempt to group by the reference value itself, won't it? Which would explain the 1:1 correlation between groups and products. :laugh:
Don't you want something like:

C#

var groups = products.GroupBy(p => p.TariffDescription);

or similar?

[edit]
A quick test:

C#

public class MyClass
    {
    public int Value { get; set; }
    public string Name { get; set; }
    }

And

C#

List<MyClass> list = new List<MyClass>();
MyClass a = new MyClass() { Value = 1, Name = "A" };
MyClass b = new MyClass() { Value = 1, Name = "B" };
MyClass c = new MyClass() { Value = 2, Name = "C" };
MyClass d = new MyClass() { Value = 2, Name = "D" };
MyClass e = new MyClass() { Value = 3, Name = "E" };
list.Add(a);
list.Add(b);
list.Add(c);
list.Add(d);
list.Add(e);
var g1 = list.GroupBy(m => m.Value);
var g2 = list.GroupBy(m => new MyClass { Value = m.Value, Name = m.Name });
Console.WriteLine(g1.Count() + ":" + g2.Count());

Gives "3:5"

Adding the IEquatable interface doesn't change that either:

C#

public class MyClass : IEquatable<MyClass>
    {
    public int Value { get; set; }
    public string Name { get; set; }
    public bool Equals(MyClass other)
        {
        return Value == other.Value;
        }
    }

I still get 3:5

[/edit]