by adam
7. October 2009 11:11
I was recently tasked with generating a string of averages based on a list of business objects. The business object has a string property called VehicleName and a decimal property called StandardMpg. The averages needed to be calculated per VehicleName, so this is to be what I group on. This took me a few minutes to wrap my mind around, but once I got it, it seemed fairly simple. I thought it would be worth sharing with the rest of you:
string averages = string.Format("Avg: {0}",
string.Join(" | ", gasMileageList
.GroupBy(x => x.VehicleName)
.Select(c => string.Format("{0} {1} MPG", c.Key, Math.Round(c.Average(x => x.StandardMpg), 1))).ToArray()));
The output will look something like: "Avg: bmw 21 MPG | kia 30 MPG"
Another option would be to dump the averages out to a list of objects, instead of a string. To do this you can do:
private class MileageAverage
{
public string VehicleName { get; set; }
public decimal Average { get; set; }
}
...
var averages = gasMileageList
.GroupBy(x => x.VehicleName)
.Select(c => new MileageAverage { VehicleName = c.Key, Average = c.Average(x => x.StandardMpg) });
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