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Oct 23rd, 2009

Body-less method declaration

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Hello

I have seen the following method syntax and I am trying to understand how this works/or doesn't:

public class MyClass
{

public MyClass();

public MyClass(string param);
}

There is no implementation of the methods (constructors) and class is not declared virtual either...
Is this something new in C# 3.0 ???

Any ideas???

Thank you

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serban

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Oct 23rd, 2009

Re: Body-less method declaration

That doesn't compile in 3.5 and I think the error message answers your question:

text Syntax (Toggle Plain Text)

'daniweb.MyClass.MyClass()' must declare a body because it is not marked abstract, extern, or partial
'daniweb.MyClass.MyClass(string)' must declare a body because it is not marked abstract, extern, or partial

Interfaces allow you to declare methods similarly but the method must have a return type:

C# Syntax (Toggle Plain Text)
  public interface ITest
  {
    void ITest();
  }
  public interface ITest
  {
    void ITest();
  }

I suspect you were looking at partial class definitions.

sknake

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Oct 23rd, 2009

Re: Body-less method declaration

Either that or the methods were abstract.

Rashakil Fol

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Oct 23rd, 2009

Re: Body-less method declaration

Click to Expand / Collapse Quote originally posted by Rashakil Fol ...

Either that or the methods were abstract.

You can't have abstract constructors since the child classes cannot implement constructors from an inherited class...

None of these are valid:

C# Syntax (Toggle Plain Text)
  public abstract class AbstractClass
  {
    abstract AbstractClass();
  }
  public abstract class AbstractClass2
  {
    AbstractClass2();
  }
  public class AbstractClass3
  {
    abstract AbstractClass3();
  }
  public abstract class AbstractClass
  {
    abstract AbstractClass();
  }
  public abstract class AbstractClass2
  {
    AbstractClass2();
  }
  public class AbstractClass3
  {
    abstract AbstractClass3();
  }

sknake

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Re: Body-less method declaration

Click to Expand / Collapse Quote originally posted by sknake ...

You can't have abstract constructors since the child classes cannot implement constructors from an inherited class...

Obviously I wasn't talking about his code example because the methods there were not marked abstract.

Rashakil Fol

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Oct 24th, 2009

Note to self: why is this title field here?

Click to Expand / Collapse Quote originally posted by serban ...

Hello

I have seen the following method syntax and I am trying to understand how this works/or doesn't:

public class MyClass
{

public MyClass();

public MyClass(string param);
}

There is no implementation of the methods (constructors) and class is not declared virtual either...
Is this something new in C# 3.0 ???

Any ideas???

Thank you

Perhaps you saw some C++ code that looks like this, which in its simplest form, is very similar in appearance. In C++, this is called forward declaration. C# does not allow forward declarations.

Last edited by DdoubleD; Oct 24th, 2009 at 9:33 am.

DdoubleD

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Sep 3rd, 2010

System.Web.Routing.Route - bodyless constructors

System.Web.Routing.Route in the source code for ASP.Net MVC 2 has these same bodyless constructors. It is not Abstract.

C# Syntax (Toggle Plain Text)
namespace System.Web.Routing
{
	public class Route : RouteBase
	{
		public Route(string url, IRouteHandler routeHandler);
 
		...
 
		public IRouteHandler RouteHandler { get; set; }
		public string Url { get; set; }
	}
}
namespace System.Web.Routing
{
	public class Route : RouteBase
	{
		public Route(string url, IRouteHandler routeHandler);

		...

		public IRouteHandler RouteHandler { get; set; }
		public string Url { get; set; }
	}
}

It would appear as though the terse Property get/set syntax is pairing with an additional terse constructor syntax that sets those public properties for you automatically, simply by having constructor parameters with the same name and type (but all lowercase instead of mixed case). Very cool... but I can't find any documentation so far to support this.

soopahman

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This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

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