Best way to serialize a double

Question

I am serializing values to an XML document. When I serialize a double, I want to make sure I am not losing any precision, and that culture will not interfere. Or any other "gotchas" that I haven't thought of.

Similarly for DateTime, I use ToBinary() to get a value that's very safe to serialize.

So, what is the best method to serialize / deserialize a double value in C#?

Answer 1

In order to parse back the exact value, you should use the G17 format specifier, as documented here:

d.ToString("G17")

or

$"{d:G17}"

Note that this can fail to roundtrip on versions below .NET Core 3.0.

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Original answer below; the "r" format specifier mentioned actually has a bug so the documentation was incorrect.

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The round-trip format specifier "r" guarantees that if you use double.Parse on the string, you will get back the exact same value:

d.ToString("r")

Answer 2

Checkout XmlConvert.ToString(double value)

This handles infinity too:

If value is Double.PositiveInfinity or Double.NegativeInfinity, this method returns the string INF or -INF respectively.