long number = …;
// string should contain exactly 12 characters
string leastSignificant48bitsOfNumberAsHex = nu开发者_如何学JAVAmber.ToString("????")
You can do it with string formatting:
string leastSignificant48bitsOfNumberAsHex = String.Format("{0:X012}", number & 0xFFFFFFFFFFFF);
This will fill up the string with zeroes if the number is shorter.
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