问题
How to cast some negative number to unsigned types
.
Type type = typeof (ushort);
short num = -100;
ushort num1 = unchecked ((ushort) num); //When type is known. Result 65436
ushort num2 = unchecked(Convert.ChangeType(num, type)); //Need here the same value
回答1:
There are only 4 types. so simply you can write your own method for that.
private static object CastToUnsigned(object number)
{
Type type = number.GetType();
unchecked
{
if (type == typeof(int)) return (uint)(int)number;
if (type == typeof(long)) return (ulong)(long)number;
if (type == typeof(short)) return (ushort)(short)number;
if (type == typeof(sbyte)) return (byte)(sbyte)number;
}
return null;
}
And here is the test:
short sh = -100;
int i = -100;
long l = -100;
Console.WriteLine(CastToUnsigned(sh));
Console.WriteLine(CastToUnsigned(i));
Console.WriteLine(CastToUnsigned(l));
Outputs
65436
4294967196
18446744073709551516
Update 10/10/2017
with C# 7.1 pattern matching feature for generic types you can now use switch statement.
thanks to @quinmars for his suggestion.
private static object CastToUnsigned<T>(T number) where T : struct
{
unchecked
{
switch (number)
{
case long xlong: return (ulong) xlong;
case int xint: return (uint)xint;
case short xshort: return (ushort) xshort;
case sbyte xsbyte: return (byte) xsbyte;
}
}
return number;
}
来源:https://stackoverflow.com/questions/33243440/cast-negative-number-to-unsigned-types-ushort-uint-or-ulong