Generic list and inheritance

[santimbs]

Hi everyone,

Lets say I have:

interface ICar
{
}

class Mercedes : ICar
{
}

Why can't I assign:

IList<ICar> cars = new List<Mercedes>();

thanks in advance,
Santi

 

[Doug Semler]

Hi everyone,

Lets say I have:

interface ICar
{
}

class Mercedes : ICar
{
}

Why can't I assign:

IList<ICar> cars = new List<Mercedes>();

thanks in advance,
Santi

MSDN and Rick Byers can explain generic type invariance better than I
could

http://msdn2.microsoft.com/en-us/library/ms228359(vs.80).aspx
http://blogs.msdn.com/rmbyers/archive/2005/02/16/375079.aspx
http://blogs.msdn.com/rmbyers/archive/2006/06/01/613690.aspx

 

[Nicholas Paldino [.NET/C# MVP]]

Santi,

Here is a response to a previous thread which answers this:

http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/msg/7c964a0781c7ec65

Basically, because while the CLR supports covariance with Generics, C#
doesn't expose that functionality.

Here is the rest of the thread with more details:

http://groups.google.com/group/micr...no+generic+covariance&rnum=2#55824f601c2e11b6

 

[santimbs]

Very explanatory links, thank you.

 

[Ben Voigt [C++ MVP]]

Santi,

Here is a response to a previous thread which answers this:

http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/msg/7c964a0781c7ec65

Basically, because while the CLR supports covariance with Generics, C#
doesn't expose that functionality.

IList, which supports both input and output, cannot be covariant (or
contravariant).

Here is the rest of the thread with more details:

http://groups.google.com/group/micr...no+generic+covariance&rnum=2#55824f601c2e11b6


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

Hi everyone,

Lets say I have:

interface ICar
{
}

class Mercedes : ICar
{
}

Why can't I assign:

IList<ICar> cars = new List<Mercedes>();

thanks in advance,
Santi