How do you get the sum of the product of two properties in an IEnumerable using LINQ?

I have an IEnumerable<dynamic> from an SQL query using Dapper, and I would like to add together the product of two properties of the dynamic objects in the IEnumerable.

I tried: 

decimal total = orderDetails.Aggregate((workingTotal, detail) => 
    workingTotal + (detail.quantity * detail.unitPrice));

but that returns an object that cannot be converted to a decimal.

Jon Skeet
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I would use Sum instead of Aggregate:

decimal total = orderDetails.Sum(x => (decimal) (x.quantity * x.unitPrice));

Depending on exactly what your situation is, I can imagine this potentially working without any casts, or needing more casts... it's not always easy to tell with dynamic.

people

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