我有一个使用反射动态创建类的应用程序。部署后,将派生类转换为其基类时出现异常。它只发生在 100 台机器中的 1 台上。所有的类都在同一个程序集中。下面是一些代码片段和在强制转换异常之前的日志消息的输出。我束手无策,非常感谢任何帮助。
//Parent class
namespace Framework.DataModel
{
[Serializable]
public class DataTreeRequest : TreeNode, IDirtyListener, ISerializable
{
....
}
}
// Derived Class
namespace Framework.DataModel
{
[Serializable]
public class CADElementRequest : DataTreeRequest
{
public CADElementRequest(String name) : base(name){}
}
}
// Method that uses reflection to create class and then cast to its base class
namespace Framework.DataModel
{
[Serializable]
public class DataModelBuilder : CoreBuilder
{
...
protected DataTreeRequest CreateDataTreeRequest(String asmName, String inName, String inType, String inSourceName)
{
DataTreeRequest dtr = null;
Assembly asm = Assembly.LoadFrom(asmName);
if (asm == null)
{
throw new BaseException("Can't find assembly " + asmName);
}
Type requestType = asm.GetType(inType);
if (requestType == null)
{
throw new BaseException("Can't find class of type " + inType + " in assembly " + asmName);
}
// Call the constructor for the tree node that takes the xml node as an argument
Type[] constructorArgsTypes = new Type[1];
constructorArgsTypes[0] = typeof(String);
ConstructorInfo constructorInfo = requestType.GetConstructor(constructorArgsTypes);
if (constructorInfo == null)
{
throw new BaseException("Can't find constructor for type " + inType + " that takes a String param");
}
Object[] constructorArgs = new Object[1];
constructorArgs[0] = inName;
Object newObj = constructorInfo.Invoke(constructorArgs);
// Code fails on this line trying to cast derived class to base class on 1 in 100 machines
dtr = newObj as DataTreeRequest;
if (dtr == null)
{
throw new BaseException("Can't cast newObj to type DataTreeRequest. newObj = " + newObj + ", Type = " + newObj.GetType().ToString());
}
dtr.InSource = inSourceName;
return dtr;
}
}
}
故障机器上的日志输出:
Message = Found assembly=Framework.DataModel, Version=1.0.5885.31486, Culture=neutral, PublicKeyToken=null
Message = newObj AssemblyQualifiedName=Framework.DataModel.CADElementRequest, Framework.DataModel, Version=1.0.5885.31486, Culture=neutral, PublicKeyToken=null, BaseType==Framework.DataModel.DataTreeRequest, FullName==Framework.DataModel.CADElementRequest
BaseException: Can't cast newObj to type DataTreeRequest. newObj = Name=Substations;InType=;InName=Substations;OutName=Substations;InSource=;OutSource=;, Type = Framework.DataModel.CADElementRequest
最佳答案
尝试替换
Assembly asm = Assembly.LoadFrom(asmName);
if (asm == null)
{
throw new BaseException("Can't find assembly " + asmName);
}
Type requestType = asm.GetType(inType);
与
Type requestType = Type.GetType(inType)
其中 inType 是程序集限定名 https://msdn.microsoft.com/en-us/library/system.type.assemblyqualifiedname(v=vs.110).aspx
如果您需要加载项目未引用的程序集,请考虑使用 Assembly.Load 方法。
关于使用 Assembly.LoadFrom 的缺点请阅读 https://msdn.microsoft.com/EN-US/library/1009fa28(v=VS.110,d=hv.2).aspx 中的备注部分
关于C# 通过反射将派生类转换为基类异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35381686/