Store/retreive from database

[rolandow]

I am trying to figure out how to store and retreive an IQuantity to a database. So basically I want to store a Quantity field and Unit as a string. When I inspect the JSON converter it seems that the string field is exploded, converted to a type, etc. etc.

I was wondering if this is really the way to go. For such a great library surely I must have missed something. I was expecting I could get the full string from QuantityInfo object, and then use that to parse it back to an IQuantity.

[angularsen]

This area could definitely be improved.
You can take inspiration from the JSON converters, but generally I would advise to take full control of how you serialize and deserialize values to be tolerant to breaking changes.

For example, one approach would be to serialize 100 cm as Value=100, Unit="Centimeter", Quantity="Length". These names are fairly rarely changed and easily obtained from unit enum types and quantity types.
However, you may need to handle breaking changes at some point in the future, if the library decides to rename "Centimeters" to "Centimetres" or similar.

Anyway, there is currently no built-in public way to parse these values.
The closest I can think of is UnitConverter.ConvertByName():

UnitsNet/UnitsNet/UnitConverter.cs

Lines 337 to 357 in ebd3275

	public static double ConvertByName(QuantityValue fromValue, string quantityName, string fromUnit, string toUnit)
	{
	if (!TryGetUnitType(quantityName, out Type? unitType))
	throw new UnitNotFoundException($"The unit type for the given quantity was not found: {quantityName}");
	if (!TryParseUnit(unitType!, fromUnit, out Enum? fromUnitValue)) // ex: LengthUnit.Meter
	{
	var e = new UnitNotFoundException($"Unit not found [{fromUnit}].");
	e.Data["unitName"] = fromUnit;
	throw e;
	}
	if (!TryParseUnit(unitType!, toUnit, out Enum? toUnitValue)) // ex: LengthUnit.Centimeter
	{
	var e = new UnitNotFoundException($"Unit not found [{toUnit}].");
	e.Data["unitName"] = toUnit;
	throw e;
	}
	return Convert(fromValue, fromUnitValue!, toUnitValue!);
	}

We could probably provide something similar, like Quantity.ParseByName("Length", "Centimeter", 100).
If you are interested in attempting a pull request, I'm happy to assist.