Convert meters to kilometers and format the value in Viewmodel

Question

I have the Viewmodel:

public class PartnerSearchResultVM
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Latitude { get; set; }
    public string Longitude { get; set; }
    public double Distance { get; set; }
    public string Classification { get; set; }
}

I get the distance in meters from the database like this: 2354,58764478263 m

I would like to present 2.35 km

How change the Viewmodel to make the convertion there (if it's the best place to do it)

Answer 1

I'd add a read-only property to your model.

public double Kilometers { get { return this.Distance / 1000; } }

If you want a formatted string back I'd create a second readonly property.

public string KilometerDisplay { 
    get { 
        return String.Format("{0:0.00}km", this.Kilometers); 
    } 
}

Although, depending on your use case, a generalized format function might be appropriate. Perhaps as an extension method:

[Extension]
public string FormatDistance(this double distance) {
    return distance.FormatDistance("");
}

[Extension]
public string FormatDistance(this double distance, string unitString) {
    return return String.Format("{0:0.00}{1}", distance, unitString);
}
// for meters:   result.Distance.FormatDistance("m");
// for kilometers:  result.Kilometers.FormatDistance("km");

Then add some XML documentation to the Distance property explaining that it is in meters.