angularsen/UnitsNet

// Construct
Length meter = Length.FromMeters(1);
Length twoMeters = new Length(2, LengthUnit.Meter);

// Convert
double cm = meter.Centimeters;         // 100
double yards = meter.Yards;            // 1.09361
double feet = meter.Feet;              // 3.28084
double inches = meter.Inches;          // 39.3701

// Pass quantity types instead of values to avoid conversion mistakes and communicate intent
string PrintPersonWeight(Mass weight)
{
    // Compile error! Newtons belong to Force, not Mass. A common source of confusion.
    double weightNewtons = weight.Newtons;

    // Convert to the unit of choice - when you need it
    return $"You weigh {weight.Kilograms:F1} kg.";
}

// Arithmetic
Length l1 = 2 * Length.FromMeters(1);
Length l2 = Length.FromMeters(1) / 2;
Length l3 = l1 + l2;

// Construct between units
Length distance = Speed.FromKilometersPerHour(80) * TimeSpan.FromMinutes(30);
Acceleration a1 = Speed.FromKilometersPerHour(80) / TimeSpan.FromSeconds(2);
Acceleration a2 = Force.FromNewtons(100) / Mass.FromKilograms(20);
RotationalSpeed r = Angle.FromDegrees(90) / TimeSpan.FromSeconds(2);

var usEnglish = new CultureInfo("en-US");
var russian = new CultureInfo("ru-RU");
var oneKg = Mass.FromKilograms(1);

// ToString() uses CurrentCulture for abbreviation language number formatting. This is consistent with the behavior of the .NET Framework,
// where DateTime.ToString() uses CurrentCulture for the whole string, likely because mixing an english date format with a russian month name might be confusing.
CultureInfo.CurrentCulture = russian;
string kgRu = oneKg.ToString(); // "1 кг"

// ToString() with specific culture and custom string format pattern
string mgUs = oneKg.ToUnit(MassUnit.Milligram).ToString(usEnglish, "unit: {1}, value: {0:F2}"); // "unit: mg, value: 1.00"
string mgRu = oneKg.ToUnit(MassUnit.Milligram).ToString(russian, "unit: {1}, value: {0:F2}"); // "unit: мг, value: 1,00"

// Parse measurement from string
Mass kg = Mass.Parse("1.0 kg", usEnglish);

// Parse unit from string, a unit can have multiple abbreviations
RotationalSpeedUnit rpm1 = RotationalSpeed.ParseUnit("rpm"); // RotationalSpeedUnit.RevolutionPerMinute
RotationalSpeedUnit rpm2 = RotationalSpeed.ParseUnit("r/min");  // RotationalSpeedUnit.RevolutionPerMinute

// Get default abbreviation for a unit, the first if more than one is defined in Length.json for Kilogram unit
string kgAbbreviation = Mass.GetAbbreviation(MassUnit.Kilogram); // "kg"

string[] names = Quantity.Names;     // ["Length", "Mass", ...]
QuantityInfo[] qis = Quantity.Infos; // All quantities and their units, types, values.

// Look up quantity by name.
QuantityInfo lengthInfo = Quantity.ByName["Length"];
UnitInfo[] lengthUnits = lengthInfo.UnitInfos;

// Look up unit by enum value (note: for extensibility, will instead look up by name in the future)
UnitInfo cmInfo = Quantity.GetUnitInfo(LengthUnit.Centimeter);

// Different ways to look up the quantity info.
QuantityInfo lengthInfo = Quantity.ByName["Length"];
lengthInfo = Length.Info;
lengthInfo = Length.FromMeters(1).QuantityInfo;

// The quantity information.
lengthInfo.Name;            // "Length"
lengthInfo.UnitInfos;       // UnitInfo[] for its units Centimeter, Meter, etc.
lengthInfo.BaseUnitInfo;    // UnitInfo for LengthUnit.Meter
lengthInfo.BaseDimensions;  // {"Length": 1, "Mass": 0, ...}
lengthInfo.UnitType;        // typeof(LengthUnit)
lengthInfo.ValueType;       // typeof(Length)
lengthInfo.Zero;            // Length.Zero

// Different ways to look up the unit info.
var cm = Quantity.GetUnitInfo(LengthUnit.Centimeter);

if (Quantity.TryGetUnitInfo(LengthUnit.Centimeter, out UnitInfo tryGetCm)) {
    cm = tryGetCm;
}

// The unit information.
cm.Value;       // Enum value: LengthUnit.Centimeter
cm.Name;        // "Centimeter"
cm.PluralName;  // "Centimeters"
cm.BaseUnits;   // {"Length": Centimeter, "Mass": null, "Time": null, ...}

IQuantity quantity = Quantity.From(3, LengthUnit.Centimeter); // Length

if (Quantity.TryFrom(3, LengthUnit.Centimeter, out IQuantity quantity2))
{
}

IQuantity quantity = Quantity.From(value: 3, quantityName: "Length", unitName: "Centimeter");

if (Quantity.TryFrom(value: 3, quantityName: "Length", unitName: "Centimeter", out IQuantity? quantity2))
{
}

// Length with unit LengthUnit.Centimeter
IQuantity quantity = Quantity.FromUnitAbbreviation(3, "cm");

if (Quantity.TryFromUnitAbbreviation(3, "cm", out IQuantity? quantity2))
{
}

IQuantity quantity = Quantity.Parse(typeof(Length), "3 cm"); // Length

if (Quantity.TryParse(typeof(Length), "3cm", out IQuantity quantity2)
{
}

Enum unit = UnitsNetSetup.Default.UnitParser.Parse("cm", typeof(LengthUnit)); // LengthUnit.Centimeter

if (UnitsNetSetup.Default.UnitParser.TryParse("cm", typeof(LengthUnit), out Enum unit2))
{
    // Use unit2 as LengthUnit.Centimeter
}

// Assume these are passed in at runtime, we don't know their values or type
Enum userSelectedUnit = LengthUnit.Millimeter;
IQuantity quantity = Length.FromCentimeters(3);

// Later we convert to a unit
quantity.ToUnit(userSelectedUnit).Value;      // 30
quantity.ToUnit(userSelectedUnit).Unit;       // LengthUnit.Millimeter
quantity.ToUnit(userSelectedUnit).ToString(); // "30 mm"
quantity.ToUnit(PressureUnit.Pascal);         // Throws exception, not compatible
quantity.As(userSelectedUnit);                // 30

UnitConverter.Convert(1, LengthUnit.Centimeter, LengthUnit.Millimeter); // 10 mm

UnitConverter.ConvertByName(1, "Length", "Centimeter", "Millimeter"); // 10 mm
UnitConverter.ConvertByAbbreviation(1, "Length", "cm", "mm"); // 10 mm

// Map unit enum values to unit abbreviations
var unitAbbreviations = UnitsNetSetup.Default.UnitAbbreviations;
unitAbbreviations.MapUnitToDefaultAbbreviation(HowMuchUnit.Some, "sm");
unitAbbreviations.GetDefaultAbbreviation(HowMuchUnit.Some); // "sm"

UnitsNetSetup.Default.UnitParser.Parse<HowMuchUnit>("sm");  // HowMuchUnit.Some

var unitConverter = UnitsNetSetup.Default.UnitConverter;
unitConverter.SetConversionFunction<HowMuch>(HowMuchUnit.Lots, HowMuchUnit.Some, x => new HowMuch(x.Value * 2, HowMuchUnit.Some));
unitConverter.SetConversionFunction<HowMuch>(HowMuchUnit.Tons, HowMuchUnit.Lots, x => new HowMuch(x.Value * 10, HowMuchUnit.Lots));
unitConverter.SetConversionFunction<HowMuch>(HowMuchUnit.Tons, HowMuchUnit.Some, x => new HowMuch(x.Value * 20, HowMuchUnit.Some));

var from = new HowMuch(10, HowMuchUnit.Tons);
IQuantity Convert(HowMuchUnit toUnit) => unitConverter.GetConversionFunction<HowMuch>(from.Unit, toUnit)(from);

Console.WriteLine($"Convert 10 tons to:");
Console.WriteLine(Convert(HowMuchUnit.Some)); // 200 sm
Console.WriteLine(Convert(HowMuchUnit.Lots)); // 100 lts
Console.WriteLine(Convert(HowMuchUnit.Tons)); // 10 tns

// Map custom units to abbreviations
var unitAbbreviationsCache = UnitsNetSetup.Default.UnitAbbreviations;
unitAbbreviationsCache.MapUnitToAbbreviation(HowMuchUnit.Some, "sm");
unitAbbreviationsCache.MapUnitToAbbreviation(HowMuchUnit.ATon, "tn");

var quantityParser = UnitsNetSetup.Default.QuantityParser;

// "1 sm" => new HowMuch(1, HowMuchUnit.Some)
HowMuch q = quantityParser.Parse<HowMuch, HowMuchUnit>(
    str: "1 sm",
    formatProvider: null,
    fromDelegate: (value, unit) => new HowMuch((double) value, unit));

// Alternatively, create your own instances to not change the global singleton instances.
var unitAbbreviationsCache = UnitAbbreviationsCache.CreateDefault(); // or .CreateEmpty()
unitAbbreviationsCache.MapUnitToAbbreviation(HowMuchUnit.Some, "sm");
unitAbbreviationsCache.MapUnitToAbbreviation(HowMuchUnit.ATon, "tn");

var quantityParser = new QuantityParser(unitAbbreviationsCache);

this.Quantities = Quantity.Names; // string[]

// or
this.Quantities = Quantity.Infos.Select(i => i.Name).ToList();

QuantityInfo quantityInfo = Quantity.ByName[quantityName];

_units.Clear();
foreach (Enum unitValue in quantityInfo.UnitInfos.Select(ui => ui.Value))
{
    _units.Add(new UnitListItem(unitValue));
}

double convertedValue = UnitConverter.Convert(
    FromValue,                      // numeric value
    SelectedFromUnit.UnitEnumValue, // Enum, such as LengthUnit.Meter
    SelectedToUnit.UnitEnumValue);  // Enum, such as LengthUnit.Centimeter