Why can I not convert from List<IScreen> to List<IRenderable> even when IScreen implements IRenderab

Posted by Blub on Stack Overflow See other posts from Stack Overflow or by Blub
Published on 2010-05-24T10:03:56Z Indexed on 2010/05/24 10:21 UTC
Read the original article Hit count: 199

Filed under:

c#

|

interface

|

contravariance

Pretty self explanatory question, glad for any answer. For me it doesn't make sense. I don't care about losing information. I just want to concatenate all my lists that inherit IRenderable somehow into a single list and then call IRenderable methods on it. I have a feeling that this is some basic rule of programming I forgot...

© Stack Overflow or respective owner

Related posts about c#

.NET WebRequest.PreAuthenticate not quite what it sounds like

as seen on West-Wind - Search for 'West-Wind'
I’ve run into the problem a few times now: How to pre-authenticate .NET WebRequest calls doing an HTTP call to the server – essentially send authentication credentials on the very first request instead of waiting for a server challenge first? At first glance this sound like it should be easy:… >>> More
HttpWebRequest and Ignoring SSL Certificate Errors

as seen on West-Wind - Search for 'West-Wind'
Man I can't believe this. I'm still mucking around with OFX servers and it drives me absolutely crazy how some these servers are just so unbelievably misconfigured. I've recently hit three different 3 major brokerages which fail HTTP validation with bad or corrupt certificates at least according to… >>> More
The dynamic Type in C# Simplifies COM Member Access from Visual FoxPro

as seen on West-Wind - Search for 'West-Wind'
I’ve written quite a bit about Visual FoxPro interoperating with .NET in the past both for ASP.NET interacting with Visual FoxPro COM objects as well as Visual FoxPro calling into .NET code via COM Interop. COM Interop with Visual FoxPro has a number of problems but one of them at least got a lot… >>> More
Dynamic Type to do away with Reflection

as seen on West-Wind - Search for 'West-Wind'
The dynamic type in C# 4.0 is a welcome addition to the language. One thing I’ve been doing a lot with it is to remove explicit Reflection code that’s often necessary when you ‘dynamically’ need to walk and object hierarchy. In the past I’ve had a number of ReflectionUtils that used string based expressions… >>> More
Finding a Relative Path in .NET

as seen on West-Wind - Search for 'West-Wind'
Here’s a nice and simple path utility that I’ve needed in a number of applications: I need to find a relative path based on a base path. So if I’m working in a folder called c:\temp\templates\ and I want to find a relative path for c:\temp\templates\subdir\test.txt I want to receive back subdir\test… >>> More

Related posts about interface

Outbound traffic being blocked for MIP/VIPped servers (Juniper SSG5)

as seen on Server Fault - Search for 'Server Fault'
As we've been having some problems with sporadic packet loss, I've been preparing a replacement router (also an SSG5) for our current Juniper SSG5. I've setup the new SSG5 identically to the old one. We have a /29 IP range with a single IP setup as a MIP map to a server and two others being used… >>> More
Allowing connections initiated from outside

as seen on Server Fault - Search for 'Server Fault'
I've got an old Juniper SSG5 running ScreenOS 5.4.0r6.0. Once a day, more or less, it'll start randomly dropping packets at a rate of ~5-10%. We currently solve this issue by simply rebooting the unit, after which it resumes working in perfect condition. As this error has started appearing randomly… >>> More
Can we define an interface within an interface?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi , I like to know can we define an interface within an interface. like interface abc { void show(); public interface xyz { void read(); } } This was question asked in interview. Any real time use of this. >>> More
Juniper SSG-5 subinterface vlan routing to the internet

as seen on Server Fault - Search for 'Server Fault'
I'm unable to get a brand new Juniper SSG-5 with latest 6.3.0r05 firmware routing to the internet from a subinterface I created on bgroup0 setup as vlan2 (bgroup0.1 on "wifi" zone). When connected on the default vlan it gets on the internet just fine. When I switch to vlan2 I'm unable to get to the… >>> More
How to change mouse pointer icon in Xfce Debian 7 Wheezy?

as seen on Super User - Search for 'Super User'
I copied the cursor theme (oxy-neon or Oxygen Neon) to /usr/share/icons and from Applications Menu - Settings - Mouse, I am able to see the new theme. I clicked on it and the pointer doesn't change. However the text typing icon ('I'), busy icon, hand icon, and resize window icons got changed. The… >>> More