How to Calculate value from Picker Length in Xamarin

Question

My purpose is to create Length converter On xamarin. I have created the picker function so that users can select what length they need to convert.

But for the next step I don't know how to create method that can handle and set the value each length and multiple with the value that prompt form users

can anyone help me with this method

namespace LengthConversion
{
   public class PickerLength 
    {
        public int rate = 0;


        public List<Length> LengthList { get; set; }

        public PickerLength()
        {
            LengthList = GetLength().OrderBy(t => t.Value).ToList();
        }

        public List<Length> GetLength()
        {
            var length = new List<Length>()
            {
                new Length() {Key = 1, Value="Millimetres(mm)"},
                new Length() {Key = 2, Value="Centimetre(cm)"},
                new Length() {Key = 3, Value="Meters(m)"},
                new Length() {Key = 4, Value="Kilometers(km)"},
                new Length() {Key = 5, Value="Feet(ft)"},
                new Length() {Key = 6, Value="Inches(in)"},
                new Length() {Key = 7, Value="Decimeter"},
                new Length() {Key = 8, Value="Mile(m)"},
                new Length() {Key = 9, Value="Yerd"},
                new Length() {Key = 10, Value="Furlong"},
                new Length() {Key = 11, Value="Hand(horses)"},
                new Length() {Key = 12, Value="Fathom"}
            };


            return length;
        }


    }


    public class Length
    {
        public int Key { get; set; }
        public string Value { get; set; }
    }

}

    <ScrollView>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="1*" />
                <RowDefinition Height="3*" />
                <RowDefinition Height="3*" />
                <RowDefinition Height="3*" />
                <RowDefinition Height="1*" />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="1*" />
                <ColumnDefinition Width="3*" />
                <ColumnDefinition Width="1*" />
            </Grid.ColumnDefinitions>
            <StackLayout Grid.Row="2" Grid.Column="1">
                <Label Text="Select Length" HorizontalTextAlignment="Center" />
                <Picker
                        ItemsSource="{Binding LengthList}"  
                        ItemDisplayBinding="{Binding Value}"
                        IsEnabled="{Binding CanConvert}" />
                <Entry
                        x:Name="ConvertSource"
                        Text="{Binding SourceValue, Mode=TwoWay}"
                        IsEnabled="{Binding CanConvert}">
                </Entry>
            </StackLayout>

            <StackLayout Grid.Row="3" Grid.Column="1">
                <Label Text="Target Length" HorizontalTextAlignment="Center" />
                <Picker
                       ItemsSource="{Binding LengthList}"  
                        ItemDisplayBinding="{Binding Value}"
                        IsEnabled="{Binding CanConvert}" />
                <Entry
                        x:Name="ConvertTarget"
                        Text="{Binding TargetValue, Mode=OneWay}"
                        IsEnabled="False" />
            </StackLayout>
        </Grid>
    </ScrollView>
</ContentPage>

namespace LengthConversion
{

    [XamlCompilation(XamlCompilationOptions.Compile)]

    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
            BindingContext = new PickerLength();
        }
    }
}

Answer 1

This can be done by choosing a reference unit of measure, like Meters. Then store the coefficient for all other units of measure. Then convert each input to the reference unit of measure and finally to the target unit of measure.

This is not the only way to accomplish this, nor a production-ready sample.

For example:

private readonly UnitOfMeatures _referenceUnits = UnitOfMeasures.Meter;

// Multiply the input values by these to get to the reference units.
// Divide the reference values by these to get to the output units.
private const double COEFFICIENT_METER = 1.0f; 
private const double COEFFICIENT_KILOMETER = 1000.0f;    
private const double COEFFICIENT_FOOT = 0.3048f;    
private const double COEFFICIENT_INCH = 0.0254f;         // use Google to find these.

// Create map of UnitOfMeasures to coefficients
private Dictionary<UnitOfMeasures, double> _coefficientMap = new Dictionary<UnitOfMeasures, double>() {
    {UnitOfMeasures.Meter, COEFFICIENT_METER}, {UnitOfMeasure.Kilometer, COEFFICIENT_KILOMETER} // etc...
};

public double ConvertUnits(UnitOfMeasures inputUnits, double value, UnitOfMeasures outputUnits) {
    double result = 0.0f;

    // convert to reference units
    result = value * _coefficientMap[inputUnits];

    // convert to output units
    result = result / _coefficientMap[outputUnits];

    return result;
}