WP7:Type.GetMethods抛出MethodAccessException。这个bug有解决方法吗?

时间:2011-04-12 17:40:29

标签: c# .net reflection windows-phone-7

我尝试获取一个类型的所有方法的列表。 Type提供GetMethods方法来执行此操作。但不幸的是,它似乎被错误地实施了。只要在反射类型上有没有重写的泛型方法,它就能正常工作。在这种特殊情况下,抛出了MethodAccessException。

有没有人对此WP7错误有解决方法?如果返回除通用方法之外的所有方法,我很好。

以下是将抛出异常的类的示例。注意:none泛型返回值旨在证明返回值不涉及问题。此外,基本方法可以改为摘要,问题仍然存在。

public abstract class BaseClassWithGenericMethod
{
    public virtual System.Collections.IList CreateList<T>()
    {
        return new List<T>();
    }
}

public class DerivedClassWithGenericMethod 
    : BaseClassWithGenericMethod
{
    public override System.Collections.IList CreateList<T>()
    {
        return new List<T>();
    }
}

5 个答案:

答案 0 :(得分:3)

我会全部抓住它们(请注意BindingFlags.DeclaredOnly中的GetMethods),然后过滤掉那些通用方法(MethodInfo.IsGenericMethod)。

对不起VB,我知道现在全世界都想要C#,但是......

Public Function GetListOfMethods() As List(Of MethodInfo)
    Dim d As New DerivedClassWithGenericMethod
    Dim myArrayMethodInfo() As Reflection.MethodInfo
    myArrayMethodInfo = d.GetType.GetMethods(BindingFlags.Instance _
                                              Or BindingFlags.Public _
                                              Or BindingFlags.DeclaredOnly)

    Dim myArrayMethodInfoList As New List(Of MethodInfo)
    For Each m As MethodInfo In myArrayMethodInfo
        If Not m.IsGenericMethod Then
            myArrayMethodInfoList.Add(m)
        End If
    Next
    Return myArrayMethodInfoList
End Function

我刚刚在WP7上使用您的示例类进行了测试,它运行正常。

答案 1 :(得分:3)

最后我开始工作了。以下Type扩展方法返回与.NET 4.0实现完全相同的结果,但没有WP7抛出的MethodAccess异常:​​

public static class TypeExtensions
{
    public static MethodInfo GetMethodWp7Workaround(this Type type, string name)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }

        return GetMethod(type, name, BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance, null, CallingConventions.Any, null, null);
    }

    public static MethodInfo GetMethodWp7Workaround(this Type type, string name, Type[] types)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }

        if (types == null)
        {
            throw new ArgumentNullException("types");
        }

        if (types.Any(t => t == null))
        {
            throw new ArgumentNullException("types");
        }

        return GetMethod(type, name, BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance, null, CallingConventions.Any, types, null);
    }

    public static MethodInfo GetMethodWp7Workaround(this Type type, string name, BindingFlags bindingAttr)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }

        return GetMethod(type, name, bindingAttr, null, CallingConventions.Any, null, null);
    }

    public static MethodInfo GetMethodWp7Workaround(this Type type, string name, Type[] types, ParameterModifier[] modifiers)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }

        if (types == null)
        {
            throw new ArgumentNullException("types");
        }

        if (types.Any(t => t == null))
        {
            throw new ArgumentNullException("types");
        }

        return GetMethod(type, name, BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance, null, CallingConventions.Any, types, modifiers);
    }

    public static MethodInfo GetMethodWp7Workaround(this Type type, string name, BindingFlags bindingAttr, Binder binder, Type[] types, ParameterModifier[] modifiers)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }

        if (types == null)
        {
            throw new ArgumentNullException("types");
        }

        if (types.Any(t => t == null))
        {
            throw new ArgumentNullException("types");
        }

        return GetMethod(type, name, bindingAttr, binder, CallingConventions.Any, types, modifiers);
    }

    public static MethodInfo GetMethodWp7Workaround(this Type type, string name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }

        if (types == null)
        {
            throw new ArgumentNullException("types");
        }

        if (types.Any(t => t == null))
        {
            throw new ArgumentNullException("types");
        }

        return GetMethod(type, name, bindingAttr, binder, callConvention, types, modifiers);
    }

    private static MethodInfo GetMethod(
        Type type, 
        string name, 
        BindingFlags bindingFlags, 
        Binder binder,
        CallingConventions callConvention,
        Type[] types,
        ParameterModifier[] modifiers)
    {
        if ((bindingFlags & BindingFlags.DeclaredOnly) == BindingFlags.DeclaredOnly)
        {
            return types == null 
                   ? type.GetMethod(name, bindingFlags)
                   : type.GetMethod(name, bindingFlags, binder, callConvention, types, modifiers);
        }

        bool isBaseType = false;
        bindingFlags = bindingFlags | BindingFlags.DeclaredOnly;
        MethodInfo result = null;
        while (result == null && type != null)
        {
            result = 
                types == null
                   ? type.GetMethod(name, bindingFlags)
                   : type.GetMethod(name, bindingFlags, binder, callConvention, types, modifiers);
            if (isBaseType && result != null && result.IsPrivate)
            {
                result = null;
            }

            type = type.BaseType;
            if (!isBaseType)
            {
                isBaseType = true;
                bindingFlags = bindingFlags & (~BindingFlags.Static);
            }
        }

        return result;
    }

    public static MethodInfo[] GetMethodsWp7Workaround(this Type type)
    {
        return type.GetMethodsWp7Workaround(BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance);
    }

    public static MethodInfo[] GetMethodsWp7Workaround(this Type type, BindingFlags flags)
    {
        if ((flags & BindingFlags.DeclaredOnly) == BindingFlags.DeclaredOnly)
        {
            return type.GetMethods(flags);
        }

        flags = flags | BindingFlags.DeclaredOnly;
        Type currentType = type;
        bool isBaseType = false;
        var methods = new List<MethodInfo>();

        while (currentType != null)
        {
            var newMethods = currentType.GetMethods(flags).Where(m => ShouldBeReturned(m, methods, isBaseType));
            methods.AddRange(newMethods);

            currentType = currentType.BaseType;
            if (!isBaseType)
            {
                isBaseType = true;
                flags = flags & (~BindingFlags.Static);
            }
        }

        return methods.ToArray();
    }

    private static bool ShouldBeReturned(
        MethodInfo method, 
        IEnumerable<MethodInfo> foundMethods,
        bool isCurrentTypeBaseType)
    {
        return !isCurrentTypeBaseType || (!method.IsPrivate && !HasAlreadyBeenFound(method, foundMethods));
    }

    private static bool HasAlreadyBeenFound(
        MethodInfo method,
        IEnumerable<MethodInfo> processedMethods)
    {
        if (!method.IsGenericMethodDefinition)
        {
            return processedMethods.Any(m => m.GetBaseDefinition().Equals(method.GetBaseDefinition()));
        }

        return processedMethods.Any(
            m => m.Name == method.Name &&
                 HaveSameGenericArguments(m, method) &&
                 HaveSameParameters(m, method));
    }

    private static bool HaveSameParameters(MethodInfo method1, MethodInfo method2)
    {
        var parameters1 = method1.GetParameters();
        var parameters2 = method2.GetParameters();
        return parameters1.Length == parameters2.Length &&
               parameters1.All(parameters2.Contains);
    }

    private static bool HaveSameGenericArguments(MethodInfo method1, MethodInfo method2)
    {
        var genericArguments1 = method1.GetGenericArguments();
        var genericArguments2 = method2.GetGenericArguments();
        return genericArguments1.Length == genericArguments2.Length;
    }
}

对于使用.NET 4.0的以下类,您将获得与WP7上的此解决方法相同的结果:

internal class TestBaseClass
{
    private static void BasePrivateStaticMethod() { }

    private void BasePrivateMethod() { }

    private void BasePrivateGenericMethod<T>() { }

    protected static void BaseProtectedStaticMethod() { }

    protected void BaseProtectedMethod() { }

    protected void BaseProtectedGenericMethod<T>() { }

    protected virtual void OverriddenProtectedMethod() { }

    protected virtual void OverriddenProtectedGenericMethod<T>() { }

    internal static void BaseInternalStaticMethod() { }

    internal void BaseInternalMethod() { }

    internal void BaseInternalGenericMethod<T>() { }

    internal virtual void OverriddenInternalMethod() { }

    internal virtual void OverriddenInternalGenericMethod<T>() { }

    public static void BasePublicStaticMethod() { }

    public void BasePublicMethod() { }

    public void BasePublicGenericMethod<T>() { }

    public virtual void OverriddenPublicMethod() { }

    public virtual void OverriddenPublicGenericMethod<T>() { }
}

internal class TestClass : TestBaseClass
{
    public string Property
    {
        get { return null; }
    }

    private static void PrivateStaticMethod() { }

    private void PrivateMethod() { }

    private void PrivateGenericMethod<T>() { }

    protected static void ProtectedStaticMethod() { }

    protected void ProtectedMethod() { }

    protected static void ProtectedGenericMethod<T>() { }

    internal static void InternalGenericMethod<T>() { }

    internal void InternalMethod() { }

    internal static void InternalStaticMethod() { }

    public static void PublicStaticMethod() { }

    public void PublicMethod() { }

    public static void PublicGenericMethod<T>() { }

    internal override void OverriddenInternalMethod()
    {
        base.OverriddenInternalMethod();
    }

    protected override void OverriddenProtectedMethod()
    {
        base.OverriddenProtectedMethod();
    }

    public override void OverriddenPublicMethod()
    {
        base.OverriddenPublicMethod();
    }

    internal override void OverriddenInternalGenericMethod<T>()
    {
        base.OverriddenInternalGenericMethod<T>();
    }

    protected override void OverriddenProtectedGenericMethod<T>()
    {
        base.OverriddenProtectedGenericMethod<T>();
    }

    public override void OverriddenPublicGenericMethod<T>()
    {
        base.OverriddenPublicGenericMethod<T>();
    }
}

答案 2 :(得分:1)

你真的会误解你所看到的行为吗?我认为您遇到了有效的安全访问问题,与WP7上的反射实现无关(除了安全模型)。

看看this post。如果您要反映的类型,在您的特定情况下,任何有问题的方法或分配给T的类型都会被security critical标记为SecurityCriticalAttribute吗?

答案 3 :(得分:1)

我必须承认我怀疑你在报道什么,但它确实很容易重现,对我来说看起来像个错误。我想你应该在Microsoft connect上报告。

至于解决方法......

这将使您获得派生类的成员,然后是基类(包括泛型),而不会出现错误:

var m = new DerivedClassWithGenericMethod();
foreach (var method in m.GetType().GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly))
    Debug.WriteLine(method.Name);

foreach (var method in m.GetType().BaseType.GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly))
    Debug.WriteLine(method.Name);

这可以是一般化的(快速和脏实现)(EqualityComprarer应该过滤掉被派生类覆盖或隐藏的基类成员):

 class MethodComparer : IEqualityComparer<MethodInfo>
    {
        public bool Equals(MethodInfo x, MethodInfo y)
        {
            return GetHashCode(x) == GetHashCode(y);
        }

        public int GetHashCode(MethodInfo obj)
        {
            int hash = obj.Name.GetHashCode();
            foreach (var param in obj.GetParameters())
                hash ^= param.ParameterType.GetHashCode();

            if (obj.IsGenericMethodDefinition)
            {
                hash ^= obj.GetGenericArguments().Length.GetHashCode();
            }
            else if (obj.IsGenericMethod)
            {
                foreach (var t in obj.GetGenericArguments())
                    hash ^= t.GetHashCode();
            }

            return hash;
        }
    }

    static class Ext
    {
        public static MethodInfo[] MyGetMethods(this Type t)
        {
            if (t == null)
                return new MethodInfo[] { };

            var methods = t.GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly);

            var baseMethods = from m in t.BaseType.MyGetMethods()
                    where !methods.Contains(m, new MethodComparer())
                    select m;

            return methods.Concat(baseMethods).ToArray();
        }
    }

var m = new DerivedClassWithGenericMethod();
foreach (var method in m.GetType().MyGetMethods())
    Debug.WriteLine(method.Name);

答案 4 :(得分:0)

Theres a GetMethods(BindingFlags)。尝试使用BindingFlags参数过滤掉你得到的方法。