如何使用LINQ获取所有不同值的总和

Question

I have ComboUniqueId and this basis I want ComboAmount, my problem is how to get distinct ComboAmount on ComboUniqueId basis please help me this, my code is below:

ComboUniqueId it is string

decimal FinalTotal = 0;

var ListUnique = this.OrderDetailArr.Select(x => new {
    ComboAmount = x.ComboAmount,
    ComboId = x.ComboId,
    ComboUniqueId = x.ComboUniqueId,
    ItemAddOnsArr = x.ItemAddOnsArr,
    TotalPrice =  x.TotalPrice
}).Distinct(x=> x.ComboUniqueId);

for (int i = 0; i < ListUnique.Length; i++)
{
    FinalTotal += ListUnique[i].TotalPrice;
    if(ListUnique[i].ComboId != null)
    {
        FinalTotal = ListUnique[i].ComboAmount;
    }
    if (ListUnique[i].ItemAddOnsArr != null)
    {
        for (int g = 0; g < this.OrderDetailArr[i].ItemAddOnsArr.Length; g++)
        {
            FinalTotal += this.OrderDetailArr[i].ItemAddOnsArr[g].AddOnTotalPrice;
        }
    }
}

Answer 1

Sounds like this.OrderDetailArr has duplicates and you want them removing.

You can do this with code similar to the following, instead of creating an anonymous object:

var ListUnique = this.OrderDetailArr
    // Group on the ComboUniqueId, you'll get 1 key with multiple values for duplicates
    .GroupBy(m => m.ComboUniqueId)
    // By retrieving the First(), you're limiting your result set to 1 per the group
    .Select(m => m.First());

The remainder of your code should work in place.

There's no need to create a new anonymous type here ( .Select(.. => new {..}) ) because you're only pulling properties from the source anyway, so you might as well keep it.

If you're set on using Distinct , you'd need an EqualityComparer<T> for your object type, that only looks at the ComboUniqueId property of the object to compare equality, you could then use that in a Distinct method as per your original code. Note that it again would not work with your anonymous type.