C# generic type

[webcliff]

Please help me to look at the following code:

-------------start----------
using System;
using System.Collecti ons.Generic;

public class GenType
{
}

public class GenericType1<Tw here T : new()
{
public static T Instance
{
get
{
return new T();
}
}

protected static string SECTION_ID;
}

public class GenericType2<T>
: GenericType1<Tw here T : new()
{
public static T Load()
{
return Instance;
}
}

public sealed class Alpha
: GenericType2<Ge nType>
{
static Alpha()
{
Console.WriteLi ne("static ctor called.");
SECTION_ID = "Alpha";
}
}

public class Test
{
public static void Main()
{
GenType o = Alpha.Load();
}
}
-------------end----------

When I run the compiled code, I don't see "static ctor called." in
output (I am not sure why not).

I intend to implement most of the code in base generic class, only
pass some values (e.g. SECTION_ID) to base class from children class
(e.g. Alpha). Instance and Load() have to be static, do you guys have
any solution?

[Jon Skeet [C# MVP]]

webcliff <we******@gmail .comwrote:

Please help me to look at the following code:

<snip>

When I run the compiled code, I don't see "static ctor called." in
output (I am not sure why not).

This is nothing to do with being generic - if you have two classes,
"Base" and "Derived" and a static method in "Base" called
MyStaticMethod, then a call to Derived.MyStati cMethod will be compiled
as Base.MyStaticMe thod - which means that the static constructor for
Derived won't get called at that point.

I intend to implement most of the code in base generic class, only
pass some values (e.g. SECTION_ID) to base class from children class
(e.g. Alpha). Instance and Load() have to be static, do you guys have
any solution?

If you want to initialize a whole bunch of classes at a particular
point in time, it's probably best to do so in some other way - such as
by having an attribute on each type that needs to be initialized, and
run through such types with reflection.

Note that you only get one SECTION_ID variable per parameter type
argument used - so if any other class derived (directly or indirectly)
from GenericType1<Ge nTypeand changed SECTION_ID, you'd have problems.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[webcliff]

On Jul 24, 6:21 pm, Jon Skeet [C# MVP] <[e-mail] mwrote:

webcliff <webcl...@gmail .comwrote:

Please help me to look at the following code:

<snip>

When I run the compiled code, I don't see "static ctor called." in
output (I am not sure why not).

This is nothing to do with being generic - if you have two classes,
"Base" and "Derived" and a static method in "Base" called
MyStaticMethod, then a call to Derived.MyStati cMethod will be compiled
as Base.MyStaticMe thod - which means that the static constructor for
Derived won't get called at that point.

m... I didn't know that, but I still wonder why the compiler want to
do this,
it is a suprise.

>

I intend to implement most of the code in base generic class, only
pass some values (e.g. SECTION_ID) to base class from children class
(e.g. Alpha). Instance and Load() have to be static, do you guys have
any solution?

If you want to initialize a whole bunch of classes at a particular
point in time, it's probably best to do so in some other way - such as
by having an attribute on each type that needs to be initialized, and
run through such types with reflection.

Classes like Alpha are auto-generated types.
What I really want is something like a parameterized generic type, I
can create
a type (i.e. Alpha) with a type GenType and a string:

public Alpha : GenericType1<Ge nType, "my id">

I am guessing this is not something DOTNET generic would like to do.

>
Note that you only get one SECTION_ID variable per parameter type
argument used - so if any other class derived (directly or indirectly)
from GenericType1<Ge nTypeand changed SECTION_ID, you'd have problems.

thanks for reminding.

>
--
Jon Skeet - <[e-mail] m>http://www.pobox.com/~skeet Blog:http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[webcliff]

On Jul 24, 6:21 pm, Jon Skeet [C# MVP] <[e-mail] mwrote:

>webcliff <webcl...@gmail .comwrote:

>>Please help me to look at the following code:

<snip>

>>When I run the compiled code, I don't see "static ctor called." in
output (I am not sure why not).

This is nothing to do with being generic - if you have two classes,
"Base" and "Derived" and a static method in "Base" called
MyStaticMethod , then a call to Derived.MyStati cMethod will be compiled
as Base.MyStaticMe thod - which means that the static constructor for
Derived won't get called at that point.

m... I didn't know that, but I still wonder why the compiler want to
do this, it is a suprise.

The meaning of "static" is that the complete information is known at
compilation time - it is statically called rather than dynamically
called. The compiler has determined that the static method in the base
class should be called, so that's the code that it emits.

>If you want to initialize a whole bunch of classes at a particular
point in time, it's probably best to do so in some other way - such as
by having an attribute on each type that needs to be initialized, and
run through such types with reflection.

Classes like Alpha are auto-generated types.

In that case you could create a static method in the auto-generated
type
which calls the static method in the base type.

What I really want is something like a parameterized generic type, I
can create
a type (i.e. Alpha) with a type GenType and a string:

public Alpha : GenericType1<Ge nType, "my id">

I am guessing this is not something DOTNET generic would like to do.

No, you can't do that.

Jon