[英]How to return derived class with C# generics
I am trying to generate some test data using NBuilder for automation for all the classes that extends a base class wherein each class will have different fields. 我正在尝试使用NBuilder为扩展基类的所有类自动化生成一些测试数据,其中每个类将具有不同的字段。
Here is my code: 这是我的代码:
public interface Interface
{
T method<T>() where T : BaseClass;
}
public class DrivedClass: BaseClass,Interface
{
public T method<T>() where T : BaseClass
{
var derviedObj = Builder<DrivedClass>.CreateNew().Build();
return derviedObj;
}
}
return derviedObj
giving error cannot implicity convert derviedObj
to T
return derviedObj
给出错误的return derviedObj
不能将derviedObj
隐式转换为T
I'm not really familiar with nbuilder, but it looks like you could try something like this: 我对nbuilder并不是很熟悉,但是看起来您可以尝试执行以下操作:
public class DrivedClass: BaseClass,Interface
{
public T method<T>() where T : BaseClass
{
var derviedObj = Builder<T>.CreateNew().Build();
return derviedObj;
}
}
Or this, if that's what you're really after: 或者,如果这就是您真正想要的:
public class DrivedClass: BaseClass,Interface
{
public T method<T>() where T : BaseClass
{
var derviedObj = Builder<DrivedClass>.CreateNew().Build();
return derviedObj as T;
}
}
Then you will get T
, but there's really no chance of knowing that it will succeed. 然后,您将得到
T
,但是实际上没有任何机会知道它会成功。 What happens when you add another implementation that doesn't inherit DrivedClass
? 当您添加另一个不继承
DrivedClass
实现时会发生什么?
public class MoreDrivedClass : BaseClass, FooInterface
{
}
Then this cast will fail: 然后此强制转换将失败:
var drivedClass = new DrivedClass();
var foo = drivedClass.method<MoreDrivedClass>();
Then you will not be able to cast DrivedClass
to MoreDrivedClass
. 这样,您将无法将
DrivedClass
为MoreDrivedClass
。 Foo
will be null. Foo
将为空。
The method can't return DerivedClass
because there is no way to know if T
is that class or some other one: 该方法无法返回
DerivedClass
因为无法知道T
是该类还是其他某个类:
SomeOtherDerived v = (new DrivedClass()).method<SomeOtherDerived>();
It is not clear what you trying to achieve, possibly something like following sample: 目前尚不清楚您要实现的目标,可能类似于以下示例:
public interface Interface<T> where T : BaseClass
{
T method();
}
public class DrivedClass: BaseClass,Interface<DerivedClass>
{
public DerivedClass method()
{
DerivedClass derviedObj = Builder<DrivedClass>.CreateNew().Build();
return derviedObj ;
}
}
Try with Activator.CreateInstance. 尝试使用Activator.CreateInstance。
public class DrivedClass: BaseClass,Interface
{
public T method<T>() where T : BaseClass
{
var derviedObj = Activator.CreateInstance(typeof(T));
return (T)derviedObj ;
}
}
DrivedClass drOb = new DrivedClass ();
var v = drOb.method<desiredType_T>();
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