c# - How to implement the DirectCast operator in a type? -

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when implementing ctype operator in custom type 1 below, type not casteable using directcast operator:

public structure colorinfo     ...     public shared widening operator ctype(byval colorinfo colorinfo) color          return color.fromargb(colorinfo.r, colorinfo.g, colorinfo.b)      end operator     ... end structure

on other hand directly assignable color object, confussing:

dim obj color = mycolorinfo

then, implement directcast operator firstly obtain typing comfort in environment (instead of using ctype) , secondly obtain beneffits, if any, of explains msdn docs here:

directcast not use visual basic run-time helper routines conversion, can provide better performance ctype when converting , data type object.

how can implement in c# or vb.net?.

directcast 'compile-time' cast added type-checking @ runtime. it's meant casting when type inheritance or interface implementation in play. not consider user defined casts, such have here, it's not applicable.

ctype appropriate , should use that, rather trying subvert language. user defined conversions , apply them.

performance-wise, ctype gets here. because types known @ compile time in example, you'll optimal code it.

to address comment: principal thing you, programmer, nothing directcast, vb.net everything. in fact, can't directcast other starting class implementing particular interface or inheriting base class.

if want provide other conversions, use ctype. fundamental split between two. directcast comes automatically , can't modify behaviour. ctype allow extend behaviour providing custom conversions.

so summarise: either class inherits type, in case directcast of instance , base type works, or doesn't, in case need create own ctype override.


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