Linq for sum of distinct addresses

问题

I have a DataTable of Products. Each product has a weight and a return address. The return address is comprised of 7 fields.

I need to cycle through the distinct addresses and sum up the total weight of product.

Example table would look like this...

Product weight  address1    address2    address3            city            state               postcode    country
A123    6       House       1st Street  some place          a city          a state             AB1 2CD     GB
A456    3       House       1st Street  some place          a city          a state             AB1 2CD     GB
A789    4       House       1st Street  some place          a city          a state             AB1 2CD     GB
A123    6       House2      2st Street  another place       another city    another state       EF2 3GH     GB
A456    3       House2      2st Street  another place       another city    another state       EF2 3GH     GB
A789    4       House2      2st Street  another place       another city    another state       EF2 3GH     GB

I would have 2 addresses returning a weight of 13.

I only need to group by the address fields (not product) and sum the weight by the address. I also need to return the country as well as the summed weight.

Is this possible using linq? Or would I be better using a SqlDataAdaptor on the DataTable? I know how I could do with with the SqlDataAdaptor but I don't know how to do with Linq and I'm guessing linq would be better for overhead?

回答1:

Group table rows by all address fields, and the calculate sum for each group:

var query = 
    from p in table.AsEnumerable()
    group p by new {
         Address1 = p.Field<string>("address1"),
         Address2 = p.Field<string>("address2"),
         Address3 = p.Field<string>("address3"),
         City = p.Field<string>("city"),
         State = p.Field<string>("state"),
         Postcode = p.Field<string>("postcode"),
         Country = p.Field<string>("country")
    } into g
    select new { 
        Address = g.Key, 
        TotalWeight = g.Sum(x => x.Field<int>("weight"))
    };

That will give you sequence of anonymous objects, which will have all address fields in Address property and sum of weights in TotalWeight property.

回答2:

The GroupBy() will group all of the products into sub-collections per distinct address. The Select() is then totalling up the weight of each sub-collection to provide the total weight.

var totals = products
        .GroupBy(p => new 
        { 
            address1 = p.Field<string>("address1"),
            address2 = p.Field<string>("address2"),
            address3 = p.Field<string>("address3"),
            city = p.Field<string>("city"),
            state = p.Field<string>("state"),
            postcode = p.Field<string>("postcode"),
            country = p.Field<string>("country")
        })
        .Select(g => new 
        {
             Total = g.Sum(p => p.Field<int>("weight"),
             Country = g.Key.country
        });

Example use:

foreach (var address in totals)
{
    Console.WriteLine(string.Format("Country: {0}, Weight: {1}", address.Country, address.Total));
}

来源：https://stackoverflow.com/questions/15474475/linq-for-sum-of-distinct-addresses

标签

linq

linq-to-dataset