您好我正在尝试动态执行以下操作 我正在使用自己的CreateInstance方法，但已经使用Activator.CreateInstance进行了测试
IPEndPoint newObject = new IPEndPoint(IPAddress.Any, 80);
当我尝试使用激活器时出现错误，无法将System.RuntimeType转换为IPAddress
public static object CreateInstance(Type context, object[] Params)
{
List<Type> argTypes = new List<Type>();
foreach (object Param in Params)
argTypes.Add(GetType(Param));
ConstructorInfo[] Types = context.GetConstructors();
foreach (ConstructorInfo node in Types)
{
ParameterInfo[] Args = node.GetParameters();
if (Params.Length == Args.Length)
{
bool[] cond = new bool[Params.Length];
for (int i = 0; i < Params.Length; i++)
if (argTypes[i] == Args[i].ParameterType) cond[i] = true;
if (cond[0] == true & cond[1] == true)
return node.Invoke(Params);
}
}
return null;
}
这就是Params在数组中的样子 [0] {Name =“IPAddress”FullName =“System.Net.IPAddress”} [1] 80
这是调用代码，prob之前应该提供它，所以你知道我正在尝试做什么，因为你可以看到它解析代表类的字符串值，这就是为什么我不能使用typeof或typeconstraints。 / p>
private object CreateInstance(ObjectCreationExpression Exp)
{
object context = GetContext(Exp.Identifier); //Gets the class type
Type t = (Type)context;
object[] Params = GetParams(Exp.ArgumentList).ToArray();
object newObject = Activator.CreateInstance(t, Params);
return newObject;
}
public static object GetContext(string classname)
{
return ParseNamespace("System.dll", classname);
}
private static object ParseNamespace(string Namespace, string classname) //Looks up class in System.dll
{
string DotNetPath = ToolLocationHelper.GetPathToDotNetFramework(TargetDotNetFrameworkVersion.VersionLatest);
Assembly Asm = Assembly.LoadFile(DotNetPath + @"\" + Namespace);
Type[] Types = Asm.GetExportedTypes();
foreach (Type Node in Types)
{
if (Node.Name == classname)
return Node;
}
return null;
}
private List<object> GetParams(NodeCollection<ArgumentNode> Params)
{
List<object> Arguments = new List<object>();
foreach (ArgumentNode node in Params)
{
if (node.Expression is MemberAccessExpression)
{
MemberAccessExpression exp = (MemberAccessExpression)node.Expression;
Type value = (Type)GetContext(exp);
string name = DirectCast<IdentifierExpression>(exp.Right).Identifier;
if (value.IsEnum)
{
string[] names = DirectCast<Type>(value).GetEnumNames();
Array item = DirectCast<Type>(value).GetEnumValues();
Arguments.Add(item.GetValue(names.ToList().IndexOf(name)));
}
else
{
Type item = value.GetMember(name)[0].ReflectedType;
Arguments.Add(item);
}
}
else
Arguments.Add((Int32)ParseType(node.Expression));
}
return Arguments;
}
ObjectCreationExpression是一个自定义类，包含用于创建新实例的已解析源代码，两个主要属性是ArgumentList，它是要用作参数的值或标识符的集合，另一个属性是我们正在创建的类型的标识符
答案 0 :(得分：0)
你已经编写了一个很好的实现来创建对象实例，但它有一些缺陷。我在下面的代码中更正了它们
public static object CreateInstance(Type context, params object[] Params) // params keyword for array
{
List<Type> argTypes = new List<Type>();
//used .GetType() method to get the appropriate type
//Param can be null so handle accordingly
foreach (object Param in Params)
argTypes.Add((Param ?? new object()).GetType());
ConstructorInfo[] Types = context.GetConstructors();
foreach (ConstructorInfo node in Types)
{
ParameterInfo[] Args = node.GetParameters();
if (Params.Length == Args.Length)
{
bool[] cond = new bool[Params.Length];
//handle derived types
for (int i = 0; i < Params.Length; i++)
if (Args[i].ParameterType.IsAssignableFrom(argTypes[i])) cond[i] = true;
if (cond[0] && cond[1])
return node.Invoke(Params);
}
}
return null;
}
调用代码
IPEndPoint newObject = (IPEndPoint)CreateInstance(typeof(IPEndPoint), IPAddress.Any, 80);
注意我可能无法纠正上面示例中的每个漏洞，我只是让它适用于您的场景，即您调用代码
泛型实施
public static T CreateInstance<T>(params object[] Params) where T : class // params keyword for array
{
List<Type> argTypes = new List<Type>();
//used .GetType() method to get the appropriate type
//Param can be null so handle accordingly
foreach (object Param in Params)
argTypes.Add((Param ?? new object()).GetType());
ConstructorInfo[] Types = typeof(T).GetConstructors();
foreach (ConstructorInfo node in Types)
{
ParameterInfo[] Args = node.GetParameters();
if (Params.Length == Args.Length)
{
bool[] cond = new bool[Params.Length];
//handle derived types
for (int i = 0; i < Params.Length; i++)
if (Args[i].ParameterType.IsAssignableFrom(argTypes[i])) cond[i] = true;
if (cond[0] && cond[1])
return (T)node.Invoke(Params);
}
}
return default(T);
}
调用代码
IPEndPoint newObject = CreateInstance<IPEndPoint>(IPAddress.Any, 80);
完全动态的对象构建
public static object CreateInstance(Type pContext, object[] Params)
{
List<Type> argTypes = new List<Type>();
//used .GetType() method to get the appropriate type
//Param can be null so handle accordingly
if (Params != null)
foreach (object Param in Params)
{
if (Param != null)
argTypes.Add(Param.GetType());
else
argTypes.Add(null);
}
ConstructorInfo[] Types = pContext.GetConstructors();
foreach (ConstructorInfo node in Types)
{
ParameterInfo[] Args = node.GetParameters();
// Params can be null for default constructors so use argTypes
if (argTypes.Count == Args.Length)
{
bool areTypesCompatible = true;
for (int i = 0; i < Params.Length; i++)
{
if (argTypes[i] == null)
{
if (Args[i].ParameterType.IsValueType)
{
//fill the defaults for value type if not supplied
Params[i] = CreateInstance(Args[i].ParameterType, null);
argTypes[i] = Params[i].GetType();
}
else
{
argTypes[i] = Args[i].ParameterType;
}
}
if (!Args[i].ParameterType.IsAssignableFrom(argTypes[i]))
{
areTypesCompatible = false;
break;
}
}
if (areTypesCompatible)
return node.Invoke(Params);
}
}
//delegate type to Activator.CreateInstance if unable to find a suitable constructor
return Activator.CreateInstance(pContext);
}
调用代码
IPEndPoint newObject = (IPEndPoint)CreateInstance(typeof(IPEndPoint), new object[] { IPAddress.Any, 80});
此代码也可以为null参数
例如
IPEndPoint newObject = (IPEndPoint)CreateInstance(typeof(IPEndPoint), new object[] { IPAddress.Any, null});
我对它进行了简化，并且还为默认构造函数处理了空参数。以及其他一些检查
因此即使您可以construct value types
例如
int obj = (int)CreateInstance(typeof(int), null);
案例示例
object context = GetContext(Exp.Identifier);
Type t = (Type)context;
object[] Params = GetParams(Exp.ArgumentList).ToArray();
//use the above defined method and it will work as expected
object newObject = CreateInstance(t, Params);
答案 1 :(得分：0)
对于它的价值，这是我对你的方法的重构：
public static object CreateInstance(Type pContext, params object[] pArguments) {
var constructors = pContext.GetConstructors();
foreach (var constructor in constructors) {
var parameters = constructor.GetParameters();
if (parameters.Length != pArguments.Length)
continue;
// assumed you wanted a matching constructor
// not just one that matches the first two types
bool fail = false;
for (int x = 0; x < parameters.Length && !fail; x++)
if (!parameters[x].ParameterType.IsInstanceOfType(pArguments[x]))
fail = true;
if (!fail)
return constructor.Invoke(pArguments);
}
return null;
}
请注意，您似乎有“参数”和“参数”的概念向后。 “参数”是接受值的方法的命名部分。 “参数”是您传递的实际值。
除此之外，听起来你的问题更多地与你传递的值有关，而不是方法的实现。