[英]Handle an exception thrown from ctor with ImportingConstructor
下面是两个类,其中一个使用ImportingConstructor导入另一个,并从ctor引发MyException。 因此,我希望在另一个类中捕获MyException,但是我得到了另一个类,即:
System.InvalidOperationException: GetExportedValue cannot be called before prerequisite import 'Class1..ctor ' has been set. (...)
如何强制MEF引发原始异常,或者至少将原始异常包装为某种异常,以便可以从代码中处理它?
[Export]
class Class1
{
public Class1()
{
(....)
throw new MyException("MyException has been thrown");
}
}
class Class2
{
[ImportingConstructor]
public Class2(Class1 class1)
{
(....)
}
}
static void Main(string[] args)
{
var catalog = new AggregateCatalog(
new AssemblyCatalog(typeof (Class1).Assembly));
CompositionContainer container = new CompositionContainer(catalog, true);
try{
Class2 class2 = container.GetExportedValue<Class2>();
}
catch(MyException ex){...}
}
AFAIK,您不能使MEF引发原始异常,但是如果进行挖掘,则原始异常在堆栈跟踪中。 因此,处理此问题的一种方法是检查CompositionException
以获取您期望的异常。 如果找到它,则可以继续进行所需的错误处理。
try
{
Class2 class2 = container.GetExportedValue<Class2>();
}
catch (CompositionException ex)
{
foreach (var cause in ex.RootCauses)
{
//Check if current cause is the Exception we're looking for
var myError = cause as MyException;
//If it's not, check the inner exception (chances are it'll be here)
if (myError == null)
myError = cause.InnerException as MyException;
if (myError != null)
{
//do what you want
}
}
}
根据引发异常的位置,可能取决于您需要在堆栈跟踪中查找的位置,但是上面的简单示例将使您走上正确的道路。 如果您有兴趣,这里是MSDN文档
为了完整起见,这是完整的实现
[Export]
class Class1
{
public Class1()
{
throw new MyException("MyException has been thrown");
}
}
[Export]
class Class2
{
[ImportingConstructor]
public Class2(Class1 class1)
{
}
}
static void Main(string[] args)
{
var catalog = new AggregateCatalog(
new AssemblyCatalog(typeof (Class1).Assembly));
CompositionContainer container = new CompositionContainer(catalog, true);
try
{
Class2 class2 = container.GetExportedValue<Class2>();
}
catch (CompositionException ex)
{
foreach (var cause in ex.RootCauses)
{
var myError = cause as MyException;
if (myError == null)
myError = cause.InnerException as MyException;
if (myError != null)
{
//do what you want
}
}
}
}
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