覆盖接口成员 [英] Overriding interface members
问题描述
我遇到了一个似乎无法解决的问题。在
中：如何覆盖我的基类的接口成员和
从我的派生类中调用重写的方法？
这是我的班级：
类RemoteXmlDataSource：System.Web.UI.WebControls.XmlDataSource
我要覆盖
DataSourceView System.Web.UI.IDataSource.GetView（string viewName）
但我想在我的
之后立即调用重写方法。 />
使用覆盖声明成员，我收到消息
修饰符''覆盖''对此项无效
尝试访问被覆盖的时成员用
（IDataSource）基础）.GetView（viewName），我收到消息
使用关键字''base''在此上下文中无效
好的我明白了，我的界面成员完全取代了基类中的成员
。有没有办法做到这一点呢？
我尝试了类似
（（IDataSource）（XmlDataSource）这个）.GetView（viewNam e）
，但这只是调用我的新成员:)
这使得比仅仅覆盖虚拟方法更加困难
并调用base.X（） ......但我希望我没有完全明白;）
亲切的问候，塞巴斯蒂安
" Sebastian" < se ************ @ googlemail.comwrote in message
news：11 ****************** **** @ u2g2000hsc.googlegro ups.com ...
我遇到了一个似乎无法解决的问题。在
中：如何覆盖我的基类的接口成员和
从我的派生类中调用重写的方法？
这是我的班级：
类RemoteXmlDataSource：System.Web.UI.WebControls.XmlDataSource
我要覆盖
DataSourceView System.Web.UI.IDataSource.GetView（string viewName）
但我想在我的
之后立即调用重写方法。 />
使用覆盖声明成员，我收到消息
修饰符''覆盖''对此项无效
您是否将基地声明为公共虚拟基地？
查看此代码是否对您有所帮助：
class Program
{
static void Main（string [] args）
{
B b = new C（）;
bM（）;
II i = b;
iM（）;
控制台.Read（）;
}
}
class B：II
{
public virtual void M（）{Console.WriteLine（" B.M"）; }
}
C级：B
{
公共覆盖无效M（）
{
Console.WriteLine（" C.M"）;
}
}
公共接口II
{
void M（）;
}
Ignacio Machin（.NET / C＃MVP）" < machin TA laceupsolutions.com写在
消息新闻：e2 ************** @ TK2MSFTNGP04.phx.gbl ...
" Sebastian" < se ************ @ googlemail.comwrote in message
news：11 ****************** **** @ u2g2000hsc.googlegro ups.com ...
>
我遇到了问题这似乎是不可解决的。在
general：如何覆盖我的基类的接口成员并从我的派生类中调用重写的方法？
这是我的班级：
类RemoteXmlDataSource：System.Web.UI.WebControls.XmlDataSource
我想覆盖
DataSourceView System.Web.UI.IDataSource.GetView（string viewName）
但是我想要在我的
之后立即调用被覆盖的方法。
用覆盖声明成员，我收到消息
修饰符''覆盖''对此无效item
您是否将基地声明为公共虚拟？
看看此代码是否对您有所帮助：
< br $>
class program
{
static void Main（string [] args）
{
B b = new C（）;
bM（）;
II i = b;
iM（） ;
Console.Read（）;
}
}
B级：II
{
public virtual void M（）{Console.WriteLine（" B.M"） ; }
我假设基类方法实现了一个接口，但是没有使用
虚拟关键字（可能会使用它）密封）。
}
class C：B
{
public覆盖void M（）
{
Console.WriteLine（" C.M"）;
}
}
公共接口II
{
void M（）;
}
事实证明，将显式接口实现声明为虚拟的
是不可能的 - 只有隐式接口实现
支持。似乎是C＃语言的限制。或者是否有我不看的
a方式？
看看这个片段：
界面IFace {
string iFaceMethod（）;
}
公共类BaseClass：IFace {
//有效（隐式接口实现）
public virtual string iFaceMethod（）{return" BaseClass public
virtual string iFaceMethod（）" ;; }
//有效（显式接口实现 - obove方法不会是
不再是一个隐式接口实现）
string IFace.iFaceMethod（）{return" BaseClass string
IFace.iFaceMethod（）" ;; }
//修饰符''public''对此项无效
//修饰符''virtual''对此无效item
//公共虚拟字符串IFace.iFaceMethod（）{}
}
公共类DerivedClass：BaseClass，IFace {
//工作
公共覆盖字符串iFaceMethod（）{
//使用关键字''base''不是在此上下文中有效
// return（（IFace）base）.iFaceMethod（）;
//工作
/ / return base.iFaceMethod（）; //调用BaseClass public virtual
string iFaceMethod（）
return" DerivedClass public override string iFaceMethod（）" ;;
}
//有效，但肯定会隐藏base.iFaceMethod
string IFace.iFaceMethod（）{
//使用关键字''base''在此上下文中无效
// return（（IFace）base）.iFaceMethod（）;
//作品
//返回base.iFaceMethod（）; //调用BaseClass public virtual
string iFaceMethod（）
//有效，但会导致无限递归
//返回（（IFace）this）.iFaceMethod（）;
return" DerivedClass string IFace.iFaceMethod（）" ;;
}
//修饰符''public''对此物品无效
//修饰符''覆盖''对此物品无效
//公共覆盖字符串IFace.iFaceMethod（）{}
}
亲切的问候，塞巴斯蒂安
Hi,
I''m confronted with a problem that seems not to be solvable. In
general: How can I override an interface member of my base class and
call the overridden method from my derived class?
This is my class:
class RemoteXmlDataSource : System.Web.UI.WebControls.XmlDataSource
And I want to override
DataSourceView System.Web.UI.IDataSource.GetView(string viewName)
but I want to make a call to the overridden method right after my
stuff.
Declaring the member with override, I get the message
The modifier ''override'' is not valid for this item
When trying to access the "overridden" member with
(IDataSource)base).GetView(viewName), I get the message
Use of keyword ''base'' is not valid in this context
Ok I understand, my interface member completely replaces the member
from the base class. Is there any way to do this even though?
I tried something like
((IDataSource)(XmlDataSource)this).GetView(viewNam e)
but that just calls my new member :)
That makes deriving much harder than just overriding a virtual method
and calling base.X()... But I hope I just did not fully understand ;)
Kind regards, Sebastian
Hi,
"Sebastian" <se************@googlemail.comwrote in message
news:11**********************@u2g2000hsc.googlegro ups.com...Hi,
I''m confronted with a problem that seems not to be solvable. In
general: How can I override an interface member of my base class and
call the overridden method from my derived class?
This is my class:
class RemoteXmlDataSource : System.Web.UI.WebControls.XmlDataSource
And I want to override
DataSourceView System.Web.UI.IDataSource.GetView(string viewName)
but I want to make a call to the overridden method right after my
stuff.
Declaring the member with override, I get the message
The modifier ''override'' is not valid for this itemDid you declare the base as public virtual?
See if this code helps you:
class Program
{
static void Main(string[] args)
{
B b = new C();
b.M();
II i = b;
i.M();
Console.Read();
}
}
class B : II
{
public virtual void M() { Console.WriteLine("B.M"); }
}
class C : B
{
public override void M()
{
Console.WriteLine("C.M");
}
}
public interface II
{
void M();
}
"Ignacio Machin ( .NET/ C# MVP )" <machin TA laceupsolutions.comwrote in
message news:e2**************@TK2MSFTNGP04.phx.gbl...Hi,
"Sebastian" <se************@googlemail.comwrote in message
news:11**********************@u2g2000hsc.googlegro ups.com...>Hi,
I''m confronted with a problem that seems not to be solvable. In
general: How can I override an interface member of my base class and
call the overridden method from my derived class?
This is my class:
class RemoteXmlDataSource : System.Web.UI.WebControls.XmlDataSource
And I want to override
DataSourceView System.Web.UI.IDataSource.GetView(string viewName)
but I want to make a call to the overridden method right after my
stuff.
Declaring the member with override, I get the message
The modifier ''override'' is not valid for this item
Did you declare the base as public virtual?
See if this code helps you:
class Program
{
static void Main(string[] args)
{
B b = new C();
b.M();
II i = b;
i.M();
Console.Read();
}
}
class B : II
{
public virtual void M() { Console.WriteLine("B.M"); }I assume that the base class method implements an interface, but doesn''t use
the virtual keyword (that might make it sealed).
}
class C : B
{
public override void M()
{
Console.WriteLine("C.M");
}
}
public interface II
{
void M();
}
It turns out that declaring explicit interface implementations as
virtual is not possible - only implicit interface implementation
support that. Seems to be a limitation of the C# language. Or is there
a way I do not see?
Look at this snippet:
interface IFace {
string iFaceMethod();
}
public class BaseClass : IFace {
// works (implicit interface implementation)
public virtual string iFaceMethod() { return "BaseClass public
virtual string iFaceMethod()"; }
// works (explicit interface implementation - obove method won''t be
anymore an implicit interface implementation)
string IFace.iFaceMethod() { return "BaseClass string
IFace.iFaceMethod()"; }
// The modifier ''public'' is not valid for this item
// The modifier ''virtual'' is not valid for this item
//public virtual string IFace.iFaceMethod() { }
}
public class DerivedClass : BaseClass, IFace {
// works
public override string iFaceMethod() {
// Use of keyword ''base'' is not valid in this context
//return ((IFace)base).iFaceMethod();
// works
//return base.iFaceMethod(); // calls BaseClass public virtual
string iFaceMethod()
return "DerivedClass public override string iFaceMethod()";
}
// works, but would definitely hide base.iFaceMethod
string IFace.iFaceMethod() {
// Use of keyword ''base'' is not valid in this context
//return ((IFace)base).iFaceMethod();
// works
//return base.iFaceMethod(); // calls BaseClass public virtual
string iFaceMethod()
// works, but leads to infinite recursion
//return ((IFace)this).iFaceMethod();
return "DerivedClass string IFace.iFaceMethod()";
}
// The modifier ''public'' is not valid for this item
// The modifier ''override'' is not valid for this item
//public override string IFace.iFaceMethod() { }
}
Kind regards, Sebastian
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