MethodBase.Invoke 方法

定義

叫用 (Invoke) 這個 MethodInfo 執行個體所反映的方法或建構函式。

多載

Invoke(Object, Object[])

使用指定的參數叫用由目前執行個體代表的方法或建構函式。

Invoke(Object, BindingFlags, Binder, Object[], CultureInfo)

在衍生類別中覆寫時,需使用指定的參數叫用反映的方法或建構函式。

Invoke(Object, Object[])

Source:
MethodBase.cs
Source:
MethodBase.cs
Source:
MethodBase.cs

使用指定的參數叫用由目前執行個體代表的方法或建構函式。

public:
 virtual System::Object ^ Invoke(System::Object ^ obj, cli::array <System::Object ^> ^ parameters);
public:
 System::Object ^ Invoke(System::Object ^ obj, cli::array <System::Object ^> ^ parameters);
public virtual object Invoke (object obj, object[] parameters);
public object? Invoke (object? obj, object?[]? parameters);
public object Invoke (object obj, object[] parameters);
abstract member Invoke : obj * obj[] -> obj
override this.Invoke : obj * obj[] -> obj
member this.Invoke : obj * obj[] -> obj
Public Overridable Function Invoke (obj As Object, parameters As Object()) As Object
Public Function Invoke (obj As Object, parameters As Object()) As Object

參數

obj
Object

要叫用方法或建構函式的物件。 如果方法是靜態的則會忽略這個引數。 如果建構函式是靜態的,此引數必須為 null,或者為定義建構函式的類別執行個體。

parameters
Object[]

叫用方法或建構函式的引數清單。 這是物件陣列,其數目、順序和型別與要叫用的方法或建構函式的參數相同。 如果沒有任何參數,parameters 應該為 null

如果此執行個體所代表的方法或建構函式採用 ref 參數 (Visual Basic 中的 ByRef),則針對該參數不需要特別的屬性以使用此函式叫用方法或建構函式。 此陣列中任何未明確使用值初始化的物件,都會包含該物件類型的預設值。 對於參考型別項目,這個值為 null。 針對實值類型項目,預設值為 0、0.0 或 false,視特定項目類型而定。

傳回

包含叫用方法之傳回值的物件,或者 null (在建構函式的情況下)。

實作

例外狀況

obj 參數為 null,且方法不是靜態的。

-或-

方法並未由 obj 類別宣告或繼承。

-或-

已叫用靜態建構函式,且 obj 不是 null 或者宣告建構函式之類別的執行個體。

注意:在 適用於 Windows 市集應用程式的 .NET可攜式類別庫中,改為攔截 Exception

parameters 陣列項目不符合此執行個體所反映之方法或建構函式的簽章。

叫用的方法或建構函式會擲回例外狀況。

-或-

目前的執行個體是包含無法驗證的程式碼的 DynamicMethod。 如需了解 DynamicMethod,請參閱<備註>中的<驗證>一節。

parameters 陣列沒有正確的引數數目。

呼叫端並沒有執行由目前執行個體所代表之方法或建構函式的權限。

注意:在 適用於 Windows 市集應用程式的 .NET可攜式類別庫中,改為攔截基類例外狀況 MemberAccessException

宣告方法的型別是開放式泛型型別。 也就是,ContainsGenericParameters 屬性會針對宣告型別傳回 true

目前的執行個體是 MethodBuilder

範例

下列程式代碼範例示範使用反映的動態方法查閱。 請注意,您無法使用基類中的 對象來叫用 MethodInfo 衍生類別中覆寫的方法,因為晚期綁定無法解析覆寫。

using namespace System;
using namespace System::Reflection;

public ref class MagicClass
{
private:
    int magicBaseValue;

public:
    MagicClass()
    {
        magicBaseValue = 9;
    }

    int ItsMagic(int preMagic)
    {
        return preMagic * magicBaseValue;
    }
};

public ref class TestMethodInfo
{
public:
    static void Main()
    {
        // Get the constructor and create an instance of MagicClass

        Type^ magicType = Type::GetType("MagicClass");
        ConstructorInfo^ magicConstructor = magicType->GetConstructor(Type::EmptyTypes);
        Object^ magicClassObject = magicConstructor->Invoke(gcnew array<Object^>(0));

        // Get the ItsMagic method and invoke with a parameter value of 100

        MethodInfo^ magicMethod = magicType->GetMethod("ItsMagic");
        Object^ magicValue = magicMethod->Invoke(magicClassObject, gcnew array<Object^>(1){100});

        Console::WriteLine("MethodInfo.Invoke() Example\n");
        Console::WriteLine("MagicClass.ItsMagic() returned: {0}", magicValue);
    }
};

int main()
{
    TestMethodInfo::Main();
}

// The example program gives the following output:
//
// MethodInfo.Invoke() Example
//
// MagicClass.ItsMagic() returned: 900
using System;
using System.Reflection;

public class MagicClass
{
    private int magicBaseValue;

    public MagicClass()
    {
        magicBaseValue = 9;
    }

    public int ItsMagic(int preMagic)
    {
        return preMagic * magicBaseValue;
    }
}

public class TestMethodInfo
{
    public static void Main()
    {
        // Get the constructor and create an instance of MagicClass

        Type magicType = Type.GetType("MagicClass");
        ConstructorInfo magicConstructor = magicType.GetConstructor(Type.EmptyTypes);
        object magicClassObject = magicConstructor.Invoke(new object[]{});

        // Get the ItsMagic method and invoke with a parameter value of 100

        MethodInfo magicMethod = magicType.GetMethod("ItsMagic");
        object magicValue = magicMethod.Invoke(magicClassObject, new object[]{100});

        Console.WriteLine("MethodInfo.Invoke() Example\n");
        Console.WriteLine("MagicClass.ItsMagic() returned: {0}", magicValue);
    }
}

// The example program gives the following output:
//
// MethodInfo.Invoke() Example
//
// MagicClass.ItsMagic() returned: 900
Imports System.Reflection

Public Class MagicClass
    Private magicBaseValue As Integer

    Public Sub New()
        magicBaseValue = 9
    End Sub

    Public Function ItsMagic(preMagic As Integer) As Integer
        Return preMagic * magicBaseValue
    End Function
End Class

Public Class TestMethodInfo
    Public Shared Sub Main()
        ' Get the constructor and create an instance of MagicClass

        Dim magicType As Type = Type.GetType("MagicClass")
        Dim magicConstructor As ConstructorInfo = magicType.GetConstructor(Type.EmptyTypes)
        Dim magicClassObject As Object = magicConstructor.Invoke(New Object(){})

        ' Get the ItsMagic method and invoke with a parameter value of 100

        Dim magicMethod As MethodInfo = magicType.GetMethod("ItsMagic")
        Dim magicValue As Object = magicMethod.Invoke(magicClassObject, New Object(){100})

        Console.WriteLine("MethodInfo.Invoke() Example" + Environment.NewLine)
        Console.WriteLine("MagicClass.ItsMagic() returned: {0}", magicValue)
    End Sub
End Class

' The example program gives the following output:
'
' MethodInfo.Invoke() Example
'
' MagicClass.ItsMagic() returned: 900

備註

這是呼叫 方法多載、Invoke(Object, BindingFlags, Binder, Object[], CultureInfo)針對 invokeAttr 和 傳遞 Defaultnullbinderculture的便利方法。

如果叫用的方法擲回例外狀況,方法會 Exception.GetBaseException 傳回原始例外狀況。

若要使用其 MethodInfo 物件叫用靜態方法,請針對 obj傳遞 null

注意

如果使用這個方法多載來叫用實例建構函式,則會重新初始化提供給 obj 的物件;也就是說,會執行所有實例初始化表達式。 傳回值是 null。 如果叫用類別建構函式,則會重新初始化類別;也就是說,會執行所有類別初始化表達式。 傳回值是 null

注意

從 .NET Framework 2.0 開始,如果呼叫端已使用 旗標授ReflectionPermissionReflectionPermissionFlag.RestrictedMemberAccess與呼叫者,而且非公用成員的授與集限制為呼叫端的授與集或子集,這個方法就可以用來存取非公用成員。 (請參閱 Reflection.) 的安全性考慮 若要使用此功能,您的應用程式應以 3.5 或更新版本為目標 .NET Framework。

如果反映方法的參數是實值型別,而 中的 parameters 對應自變數為 null,則運行時間會傳遞實值型別的零初始化實例。

另請參閱

適用於

Invoke(Object, BindingFlags, Binder, Object[], CultureInfo)

Source:
MethodBase.cs
Source:
MethodBase.cs
Source:
MethodBase.cs

在衍生類別中覆寫時,需使用指定的參數叫用反映的方法或建構函式。

public:
 abstract System::Object ^ Invoke(System::Object ^ obj, System::Reflection::BindingFlags invokeAttr, System::Reflection::Binder ^ binder, cli::array <System::Object ^> ^ parameters, System::Globalization::CultureInfo ^ culture);
public abstract object? Invoke (object? obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder? binder, object?[]? parameters, System.Globalization.CultureInfo? culture);
public abstract object Invoke (object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, object[] parameters, System.Globalization.CultureInfo culture);
abstract member Invoke : obj * System.Reflection.BindingFlags * System.Reflection.Binder * obj[] * System.Globalization.CultureInfo -> obj
Public MustOverride Function Invoke (obj As Object, invokeAttr As BindingFlags, binder As Binder, parameters As Object(), culture As CultureInfo) As Object

參數

obj
Object

要叫用方法或建構函式的物件。 如果方法是靜態的則會忽略這個引數。 如果建構函式是靜態的,此引數必須為 null,或者為定義建構函式的類別執行個體。

invokeAttr
BindingFlags

由零或來自 BindingFlags 的多個位元旗標組成的位元遮罩。

binder
Binder

使用反映來啟用繫結、強制引數的類型、成員的引動過程,和擷取 MemberInfo 物件的物件。 如果 bindernull,則會使用預設繫結器。

parameters
Object[]

叫用方法或建構函式的引數清單。 這是物件陣列,其數目、順序和型別與要叫用的方法或建構函式的參數相同。 如果沒有參數,這應該是 null

如果這個執行個體表示的方法或建構函式採用 ByRef 參數,該參數就不需要有特殊屬性,就能夠以這個函式叫用方法或建構函式。 此陣列中任何未明確使用值初始化的物件,都會包含該物件類型的預設值。 對於參考型別項目,這個值為 null。 對於實值型別項目,這個值為 0、0.0 或 false,由特定的項目類型決定。

culture
CultureInfo

CultureInfo 的執行個體,用於管理類型的強制型轉。 如果這是 null,會使用目前執行緒的 CultureInfo。 (例如,要將代表 1000 的字串轉換成 Double 值時,這是必要的,因為 1000 的表示方式會因不同文化特性而有所不同。)

傳回

Object,包含叫用方法的傳回值,但如果是建構函式,則為 null,如果方法的傳回型別為 null,則為 void。 呼叫方法或建構函式之前,Invoke 會檢查使用者是否有存取權限,並驗證參數是否有效。

實作

例外狀況

obj 參數為 null,且方法不是靜態的。

-或-

方法並未由 obj 類別宣告或繼承。

-或-

已叫用靜態建構函式,且 obj 不是 null 或者宣告建構函式之類別的執行個體。

parameters 參數的型別與這個執行個體反映的方法或建構函式的簽章不相符。

parameters 陣列沒有正確的引數數目。

叫用的方法或建構函式會擲回例外狀況。

呼叫端並沒有執行由目前執行個體所代表之方法或建構函式的權限。

宣告方法的型別是開放式泛型型別。 也就是,ContainsGenericParameters 屬性會針對宣告型別傳回 true

範例

下列範例示範 類別的所有成員 System.Reflection.Binder 使用 的多 Type.InvokeMember載。 私用方法 CanConvertFrom 會尋找指定類型的相容型別。 如需在自定義系結案例中叫用成員的另一個範例,請參閱 動態載入和使用類型

using namespace System;
using namespace System::Reflection;
using namespace System::Globalization;
using namespace System::Runtime::InteropServices;
public ref class MyBinder: public Binder
{
public:
   MyBinder()
      : Binder()
   {}

private:
   ref class BinderState
   {
   public:
      array<Object^>^args;
   };

public:
   virtual FieldInfo^ BindToField( BindingFlags bindingAttr, array<FieldInfo^>^match, Object^ value, CultureInfo^ culture ) override
   {
      if ( match == nullptr )
            throw gcnew ArgumentNullException( "match" );

      // Get a field for which the value parameter can be converted to the specified field type.
      for ( int i = 0; i < match->Length; i++ )
         if ( ChangeType( value, match[ i ]->FieldType, culture ) != nullptr )
                  return match[ i ];

      return nullptr;
   }

   virtual MethodBase^ BindToMethod( BindingFlags bindingAttr, array<MethodBase^>^match, array<Object^>^%args, array<ParameterModifier>^ modifiers, CultureInfo^ culture, array<String^>^names, [Out]Object^% state ) override
   {
      // Store the arguments to the method in a state Object*.
      BinderState^ myBinderState = gcnew BinderState;
      array<Object^>^arguments = gcnew array<Object^>(args->Length);
      args->CopyTo( arguments, 0 );
      myBinderState->args = arguments;
      state = myBinderState;
      if ( match == nullptr )
            throw gcnew ArgumentNullException;

      // Find a method that has the same parameters as those of the args parameter.
      for ( int i = 0; i < match->Length; i++ )
      {
         // Count the number of parameters that match.
         int count = 0;
         array<ParameterInfo^>^parameters = match[ i ]->GetParameters();

         // Go on to the next method if the number of parameters do not match.
         if ( args->Length != parameters->Length )
                  continue;

         // Match each of the parameters that the user expects the method to have.
         for ( int j = 0; j < args->Length; j++ )
         {
            // If the names parameter is not 0, then reorder args.
            if ( names != nullptr )
            {
               if ( names->Length != args->Length )
                              throw gcnew ArgumentException( "names and args must have the same number of elements." );

               for ( int k = 0; k < names->Length; k++ )
                  if ( String::Compare( parameters[ j ]->Name, names[ k ] ) == 0 )
                                    args[ j ] = myBinderState->args[ k ];
            }

            // Determine whether the types specified by the user can be converted to the parameter type.
            if ( ChangeType( args[ j ], parameters[ j ]->ParameterType, culture ) != nullptr )
                        count += 1;
            else
                        break;
         }
         if ( count == args->Length )
                  return match[ i ];
      }
      return nullptr;
   }

   virtual Object^ ChangeType( Object^ value, Type^ myChangeType, CultureInfo^ culture ) override
   {
      // Determine whether the value parameter can be converted to a value of type myType.
      if ( CanConvertFrom( value->GetType(), myChangeType ) )
         // Return the converted Object*.
         return Convert::ChangeType( value, myChangeType ); 
      else
         return nullptr;
   }

   virtual void ReorderArgumentArray( array<Object^>^%args, Object^ state ) override
   {
      // Return the args that had been reordered by BindToMethod.
      (safe_cast<BinderState^>(state))->args->CopyTo( args, 0 );
   }

   virtual MethodBase^ SelectMethod( BindingFlags bindingAttr, array<MethodBase^>^match, array<Type^>^types, array<ParameterModifier>^ modifiers ) override
   {
      if ( match == nullptr )
            throw gcnew ArgumentNullException( "match" );

      for ( int i = 0; i < match->Length; i++ )
      {
         // Count the number of parameters that match.
         int count = 0;
         array<ParameterInfo^>^parameters = match[ i ]->GetParameters();

         // Go on to the next method if the number of parameters do not match.
         if ( types->Length != parameters->Length )
                  continue;

         // Match each of the parameters that the user expects the method to have.
         for ( int j = 0; j < types->Length; j++ )
         {
            // Determine whether the types specified by the user can be converted to parameter type.
            if ( CanConvertFrom( types[ j ], parameters[ j ]->ParameterType ) )
                        count += 1;
            else
                        break;
         }
         // Determine whether the method has been found.
         if ( count == types->Length )
                  return match[ i ];
      }
      return nullptr;
   }

   virtual PropertyInfo^ SelectProperty( BindingFlags bindingAttr, array<PropertyInfo^>^match, Type^ returnType, array<Type^>^indexes, array<ParameterModifier>^ modifiers ) override
   {
      if ( match == nullptr )
            throw gcnew ArgumentNullException( "match" );

      for ( int i = 0; i < match->Length; i++ )
      {
         // Count the number of indexes that match.
         int count = 0;
         array<ParameterInfo^>^parameters = match[ i ]->GetIndexParameters();

         // Go on to the next property if the number of indexes do not match.
         if ( indexes->Length != parameters->Length )
                  continue;

         // Match each of the indexes that the user expects the property to have.
         for ( int j = 0; j < indexes->Length; j++ )
            // Determine whether the types specified by the user can be converted to index type.
            if ( CanConvertFrom( indexes[ j ], parameters[ j ]->ParameterType ) )
                        count += 1;
            else
                        break;

         // Determine whether the property has been found.
         if ( count == indexes->Length )
         {
            // Determine whether the return type can be converted to the properties type.
            if ( CanConvertFrom( returnType, match[ i ]->PropertyType ) )
                  return match[ i ];
            else
                  continue;
         }
      }
      return nullptr;
   }

private:

   // Determines whether type1 can be converted to type2. Check only for primitive types.
   bool CanConvertFrom( Type^ type1, Type^ type2 )
   {
      if ( type1->IsPrimitive && type2->IsPrimitive )
      {
         TypeCode typeCode1 = Type::GetTypeCode( type1 );
         TypeCode typeCode2 = Type::GetTypeCode( type2 );

         // If both type1 and type2 have the same type, return true.
         if ( typeCode1 == typeCode2 )
                  return true;

         // Possible conversions from Char follow.
         if ( typeCode1 == TypeCode::Char )
         {
            switch ( typeCode2 )
            {
               case TypeCode::UInt16:
                  return true;

               case TypeCode::UInt32:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Byte follow.
         if ( typeCode1 == TypeCode::Byte )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Char:
                  return true;

               case TypeCode::UInt16:
                  return true;

               case TypeCode::Int16:
                  return true;

               case TypeCode::UInt32:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from SByte follow.
         if ( typeCode1 == TypeCode::SByte )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Int16:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from UInt16 follow.
         if ( typeCode1 == TypeCode::UInt16 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::UInt32:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Int16 follow.
         if ( typeCode1 == TypeCode::Int16 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Int32:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from UInt32 follow.
         if ( typeCode1 == TypeCode::UInt32 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Int32 follow.
         if ( typeCode1 == TypeCode::Int32 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from UInt64 follow.
         if ( typeCode1 == TypeCode::UInt64 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Int64 follow.
         if ( typeCode1 == TypeCode::Int64 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Single follow.
         if ( typeCode1 == TypeCode::Single )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }
      }

      return false;
   }

};

public ref class MyClass1
{
public:
   short myFieldB;
   int myFieldA;
   void MyMethod( long i, char k )
   {
      Console::WriteLine( "\nThis is MyMethod(long i, char k)" );
   }

   void MyMethod( long i, long j )
   {
      Console::WriteLine( "\nThis is MyMethod(long i, long j)" );
   }
};

int main()
{
   // Get the type of MyClass1.
   Type^ myType = MyClass1::typeid;

   // Get the instance of MyClass1.
   MyClass1^ myInstance = gcnew MyClass1;
   Console::WriteLine( "\nDisplaying the results of using the MyBinder binder.\n" );

   // Get the method information for MyMethod.
   array<Type^>^types = {short::typeid,short::typeid};
   MethodInfo^ myMethod = myType->GetMethod( "MyMethod", static_cast<BindingFlags>(BindingFlags::Public | BindingFlags::Instance), gcnew MyBinder, types, nullptr );
   Console::WriteLine( myMethod );

   // Invoke MyMethod.
   array<Object^>^obj = {32,32};
   myMethod->Invoke( myInstance, BindingFlags::InvokeMethod, gcnew MyBinder, obj, CultureInfo::CurrentCulture );
}
using System;
using System.Reflection;
using System.Globalization;

public class MyBinder : Binder
{
    public MyBinder() : base()
    {
    }
    private class BinderState
    {
        public object[] args;
    }
    public override FieldInfo BindToField(
        BindingFlags bindingAttr,
        FieldInfo[] match,
        object value,
        CultureInfo culture
        )
    {
        if(match == null)
            throw new ArgumentNullException("match");
        // Get a field for which the value parameter can be converted to the specified field type.
        for(int i = 0; i < match.Length; i++)
            if(ChangeType(value, match[i].FieldType, culture) != null)
                return match[i];
        return null;
    }
    public override MethodBase BindToMethod(
        BindingFlags bindingAttr,
        MethodBase[] match,
        ref object[] args,
        ParameterModifier[] modifiers,
        CultureInfo culture,
        string[] names,
        out object state
        )
    {
        // Store the arguments to the method in a state object.
        BinderState myBinderState = new BinderState();
        object[] arguments = new Object[args.Length];
        args.CopyTo(arguments, 0);
        myBinderState.args = arguments;
        state = myBinderState;
        if(match == null)
            throw new ArgumentNullException();
        // Find a method that has the same parameters as those of the args parameter.
        for(int i = 0; i < match.Length; i++)
        {
            // Count the number of parameters that match.
            int count = 0;
            ParameterInfo[] parameters = match[i].GetParameters();
            // Go on to the next method if the number of parameters do not match.
            if(args.Length != parameters.Length)
                continue;
            // Match each of the parameters that the user expects the method to have.
            for(int j = 0; j < args.Length; j++)
            {
                // If the names parameter is not null, then reorder args.
                if(names != null)
                {
                    if(names.Length != args.Length)
                        throw new ArgumentException("names and args must have the same number of elements.");
                    for(int k = 0; k < names.Length; k++)
                        if(String.Compare(parameters[j].Name, names[k].ToString()) == 0)
                            args[j] = myBinderState.args[k];
                }
                // Determine whether the types specified by the user can be converted to the parameter type.
                if(ChangeType(args[j], parameters[j].ParameterType, culture) != null)
                    count += 1;
                else
                    break;
            }
            // Determine whether the method has been found.
            if(count == args.Length)
                return match[i];
        }
        return null;
    }
    public override object ChangeType(
        object value,
        Type myChangeType,
        CultureInfo culture
        )
    {
        // Determine whether the value parameter can be converted to a value of type myType.
        if(CanConvertFrom(value.GetType(), myChangeType))
            // Return the converted object.
            return Convert.ChangeType(value, myChangeType);
        else
            // Return null.
            return null;
    }
    public override void ReorderArgumentArray(
        ref object[] args,
        object state
        )
    {
        // Return the args that had been reordered by BindToMethod.
        ((BinderState)state).args.CopyTo(args, 0);
    }
    public override MethodBase SelectMethod(
        BindingFlags bindingAttr,
        MethodBase[] match,
        Type[] types,
        ParameterModifier[] modifiers
        )
    {
        if(match == null)
            throw new ArgumentNullException("match");
        for(int i = 0; i < match.Length; i++)
        {
            // Count the number of parameters that match.
            int count = 0;
            ParameterInfo[] parameters = match[i].GetParameters();
            // Go on to the next method if the number of parameters do not match.
            if(types.Length != parameters.Length)
                continue;
            // Match each of the parameters that the user expects the method to have.
            for(int j = 0; j < types.Length; j++)
                // Determine whether the types specified by the user can be converted to parameter type.
                if(CanConvertFrom(types[j], parameters[j].ParameterType))
                    count += 1;
                else
                    break;
            // Determine whether the method has been found.
            if(count == types.Length)
                return match[i];
        }
        return null;
    }
    public override PropertyInfo SelectProperty(
        BindingFlags bindingAttr,
        PropertyInfo[] match,
        Type returnType,
        Type[] indexes,
        ParameterModifier[] modifiers
        )
    {
        if(match == null)
            throw new ArgumentNullException("match");
        for(int i = 0; i < match.Length; i++)
        {
            // Count the number of indexes that match.
            int count = 0;
            ParameterInfo[] parameters = match[i].GetIndexParameters();
            // Go on to the next property if the number of indexes do not match.
            if(indexes.Length != parameters.Length)
                continue;
            // Match each of the indexes that the user expects the property to have.
            for(int j = 0; j < indexes.Length; j++)
                // Determine whether the types specified by the user can be converted to index type.
                if(CanConvertFrom(indexes[j], parameters[j].ParameterType))
                    count += 1;
                else
                    break;
            // Determine whether the property has been found.
            if(count == indexes.Length)
                // Determine whether the return type can be converted to the properties type.
                if(CanConvertFrom(returnType, match[i].PropertyType))
                    return match[i];
                else
                    continue;
        }
        return null;
    }
    // Determines whether type1 can be converted to type2. Check only for primitive types.
    private bool CanConvertFrom(Type type1, Type type2)
    {
        if(type1.IsPrimitive && type2.IsPrimitive)
        {
            TypeCode typeCode1 = Type.GetTypeCode(type1);
            TypeCode typeCode2 = Type.GetTypeCode(type2);
            // If both type1 and type2 have the same type, return true.
            if(typeCode1 == typeCode2)
                return true;
            // Possible conversions from Char follow.
            if(typeCode1 == TypeCode.Char)
                switch(typeCode2)
                {
                    case TypeCode.UInt16 : return true;
                    case TypeCode.UInt32 : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Byte follow.
            if(typeCode1 == TypeCode.Byte)
                switch(typeCode2)
                {
                    case TypeCode.Char   : return true;
                    case TypeCode.UInt16 : return true;
                    case TypeCode.Int16  : return true;
                    case TypeCode.UInt32 : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from SByte follow.
            if(typeCode1 == TypeCode.SByte)
                switch(typeCode2)
                {
                    case TypeCode.Int16  : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from UInt16 follow.
            if(typeCode1 == TypeCode.UInt16)
                switch(typeCode2)
                {
                    case TypeCode.UInt32 : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Int16 follow.
            if(typeCode1 == TypeCode.Int16)
                switch(typeCode2)
                {
                    case TypeCode.Int32  : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from UInt32 follow.
            if(typeCode1 == TypeCode.UInt32)
                switch(typeCode2)
                {
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Int32 follow.
            if(typeCode1 == TypeCode.Int32)
                switch(typeCode2)
                {
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from UInt64 follow.
            if(typeCode1 == TypeCode.UInt64)
                switch(typeCode2)
                {
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Int64 follow.
            if(typeCode1 == TypeCode.Int64)
                switch(typeCode2)
                {
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Single follow.
            if(typeCode1 == TypeCode.Single)
                switch(typeCode2)
                {
                    case TypeCode.Double : return true;
                    default              : return false;
                }
        }
        return false;
    }
}
public class MyClass1
{
    public short myFieldB;
    public int myFieldA;
    public void MyMethod(long i, char k)
    {
        Console.WriteLine("\nThis is MyMethod(long i, char k)");
    }
    public void MyMethod(long i, long j)
    {
        Console.WriteLine("\nThis is MyMethod(long i, long j)");
    }
}
public class Binder_Example
{
    public static void Main()
    {
        // Get the type of MyClass1.
        Type myType = typeof(MyClass1);
        // Get the instance of MyClass1.
        MyClass1 myInstance = new MyClass1();
        Console.WriteLine("\nDisplaying the results of using the MyBinder binder.\n");
        // Get the method information for MyMethod.
        MethodInfo myMethod = myType.GetMethod("MyMethod", BindingFlags.Public | BindingFlags.Instance,
            new MyBinder(), new Type[] {typeof(short), typeof(short)}, null);
        Console.WriteLine(myMethod);
        // Invoke MyMethod.
        myMethod.Invoke(myInstance, BindingFlags.InvokeMethod, new MyBinder(), new Object[] {(int)32, (int)32}, CultureInfo.CurrentCulture);
    }
}
Imports System.Reflection
Imports System.Globalization

Public Class MyBinder
    Inherits Binder
    Public Sub New()
        MyBase.new()
    End Sub
    Private Class BinderState
        Public args() As Object
    End Class

    Public Overrides Function BindToField(ByVal bindingAttr As BindingFlags, ByVal match() As FieldInfo, ByVal value As Object, ByVal culture As CultureInfo) As FieldInfo
        If match Is Nothing Then
            Throw New ArgumentNullException("match")
        End If
        ' Get a field for which the value parameter can be converted to the specified field type.
        Dim i As Integer
        For i = 0 To match.Length - 1
            If Not (ChangeType(value, match(i).FieldType, culture) Is Nothing) Then
                Return match(i)
            End If
        Next i
        Return Nothing
    End Function 'BindToField

    Public Overrides Function BindToMethod(ByVal bindingAttr As BindingFlags, ByVal match() As MethodBase, ByRef args() As Object, ByVal modifiers() As ParameterModifier, ByVal culture As CultureInfo, ByVal names() As String, ByRef state As Object) As MethodBase
        ' Store the arguments to the method in a state object.
        Dim myBinderState As New BinderState()
        Dim arguments() As Object = New [Object](args.Length) {}
        args.CopyTo(arguments, 0)
        myBinderState.args = arguments
        state = myBinderState

        If match Is Nothing Then
            Throw New ArgumentNullException()
        End If
        ' Find a method that has the same parameters as those of args.
        Dim i As Integer
        For i = 0 To match.Length - 1
            ' Count the number of parameters that match.
            Dim count As Integer = 0
            Dim parameters As ParameterInfo() = match(i).GetParameters()
            ' Go on to the next method if the number of parameters do not match.
            If args.Length <> parameters.Length Then
                GoTo ContinueFori
            End If
            ' Match each of the parameters that the user expects the method to have.
            Dim j As Integer
            For j = 0 To args.Length - 1
                ' If names is not null, then reorder args.
                If Not (names Is Nothing) Then
                    If names.Length <> args.Length Then
                        Throw New ArgumentException("names and args must have the same number of elements.")
                    End If
                    Dim k As Integer
                    For k = 0 To names.Length - 1
                        If String.Compare(parameters(j).Name, names(k).ToString()) = 0 Then
                            args(j) = myBinderState.args(k)
                        End If
                    Next k
                End If ' Determine whether the types specified by the user can be converted to parameter type.
                If Not (ChangeType(args(j), parameters(j).ParameterType, culture) Is Nothing) Then
                    count += 1
                Else
                    Exit For
                End If
            Next j
            ' Determine whether the method has been found.
            If count = args.Length Then
                Return match(i)
            End If
ContinueFori:
        Next i
        Return Nothing
    End Function 'BindToMethod

    Public Overrides Function ChangeType(ByVal value As Object, ByVal myChangeType As Type, ByVal culture As CultureInfo) As Object
        ' Determine whether the value parameter can be converted to a value of type myType.
        If CanConvertFrom(value.GetType(), myChangeType) Then
            ' Return the converted object.
            Return Convert.ChangeType(value, myChangeType)
            ' Return null.
        Else
            Return Nothing
        End If
    End Function 'ChangeType

    Public Overrides Sub ReorderArgumentArray(ByRef args() As Object, ByVal state As Object)
        'Redimension the array to hold the state values.
        ReDim args(CType(state, BinderState).args.Length)
        ' Return the args that had been reordered by BindToMethod.
        CType(state, BinderState).args.CopyTo(args, 0)
    End Sub

    Public Overrides Function SelectMethod(ByVal bindingAttr As BindingFlags, ByVal match() As MethodBase, ByVal types() As Type, ByVal modifiers() As ParameterModifier) As MethodBase
        If match Is Nothing Then
            Throw New ArgumentNullException("match")
        End If
        Dim i As Integer
        For i = 0 To match.Length - 1
            ' Count the number of parameters that match.
            Dim count As Integer = 0
            Dim parameters As ParameterInfo() = match(i).GetParameters()
            ' Go on to the next method if the number of parameters do not match.
            If types.Length <> parameters.Length Then
                GoTo ContinueFori
            End If
            ' Match each of the parameters that the user expects the method to have.
            Dim j As Integer
            For j = 0 To types.Length - 1
                ' Determine whether the types specified by the user can be converted to parameter type.
                If CanConvertFrom(types(j), parameters(j).ParameterType) Then
                    count += 1
                Else
                    Exit For
                End If
            Next j ' Determine whether the method has been found.
            If count = types.Length Then
                Return match(i)
            End If
ContinueFori:
        Next i
        Return Nothing
    End Function 'SelectMethod
    Public Overrides Function SelectProperty(ByVal bindingAttr As BindingFlags, ByVal match() As PropertyInfo, ByVal returnType As Type, ByVal indexes() As Type, ByVal modifiers() As ParameterModifier) As PropertyInfo
        If match Is Nothing Then
            Throw New ArgumentNullException("match")
        End If
        Dim i As Integer
        For i = 0 To match.Length - 1
            ' Count the number of indexes that match.
            Dim count As Integer = 0
            Dim parameters As ParameterInfo() = match(i).GetIndexParameters()

            ' Go on to the next property if the number of indexes do not match.
            If indexes.Length <> parameters.Length Then
                GoTo ContinueFori
            End If
            ' Match each of the indexes that the user expects the property to have.
            Dim j As Integer
            For j = 0 To indexes.Length - 1
                ' Determine whether the types specified by the user can be converted to index type.
                If CanConvertFrom(indexes(j), parameters(j).ParameterType) Then
                    count += 1
                Else
                    Exit For
                End If
            Next j ' Determine whether the property has been found.
            If count = indexes.Length Then
                ' Determine whether the return type can be converted to the properties type.
                If CanConvertFrom(returnType, match(i).PropertyType) Then
                    Return match(i)
                Else
                    GoTo ContinueFori
                End If
            End If
ContinueFori:
        Next i
        Return Nothing
    End Function 'SelectProperty

    ' Determine whether type1 can be converted to type2. Check only for primitive types.
    Private Function CanConvertFrom(ByVal type1 As Type, ByVal type2 As Type) As Boolean
        If type1.IsPrimitive And type2.IsPrimitive Then
            Dim typeCode1 As TypeCode = Type.GetTypeCode(type1)
            Dim typeCode2 As TypeCode = Type.GetTypeCode(type2)
            ' If both type1 and type2 have same type, return true.
            If typeCode1 = typeCode2 Then
                Return True
            End If ' Possible conversions from Char follow.
            If typeCode1 = TypeCode.Char Then
                Select Case typeCode2
                    Case TypeCode.UInt16
                        Return True
                    Case TypeCode.UInt32
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Byte follow.
            If typeCode1 = TypeCode.Byte Then
                Select Case typeCode2
                    Case TypeCode.Char
                        Return True
                    Case TypeCode.UInt16
                        Return True
                    Case TypeCode.Int16
                        Return True
                    Case TypeCode.UInt32
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from SByte follow.
            If typeCode1 = TypeCode.SByte Then
                Select Case typeCode2
                    Case TypeCode.Int16
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from UInt16 follow.
            If typeCode1 = TypeCode.UInt16 Then
                Select Case typeCode2
                    Case TypeCode.UInt32
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Int16 follow.
            If typeCode1 = TypeCode.Int16 Then
                Select Case typeCode2
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from UInt32 follow.
            If typeCode1 = TypeCode.UInt32 Then
                Select Case typeCode2
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Int32 follow.
            If typeCode1 = TypeCode.Int32 Then
                Select Case typeCode2
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from UInt64 follow.
            If typeCode1 = TypeCode.UInt64 Then
                Select Case typeCode2
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Int64 follow.
            If typeCode1 = TypeCode.Int64 Then
                Select Case typeCode2
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Single follow.
            If typeCode1 = TypeCode.Single Then
                Select Case typeCode2
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If
        End If
        Return False
    End Function 'CanConvertFrom
End Class


Public Class MyClass1
    Public myFieldB As Short
    Public myFieldA As Integer

    Public Overloads Sub MyMethod(ByVal i As Long, ByVal k As Char)
        Console.WriteLine(ControlChars.NewLine & "This is MyMethod(long i, char k).")
    End Sub

    Public Overloads Sub MyMethod(ByVal i As Long, ByVal j As Long)
        Console.WriteLine(ControlChars.NewLine & "This is MyMethod(long i, long j).")
    End Sub
End Class


Public Class Binder_Example
    Public Shared Sub Main()
        ' Get the type of MyClass1.
        Dim myType As Type = GetType(MyClass1)
        ' Get the instance of MyClass1.
        Dim myInstance As New MyClass1()
        Console.WriteLine(ControlChars.Cr & "Displaying the results of using the MyBinder binder.")
        Console.WriteLine()
        ' Get the method information for MyMethod.
        Dim myMethod As MethodInfo = myType.GetMethod("MyMethod", BindingFlags.Public Or BindingFlags.Instance, New MyBinder(), New Type() {GetType(Short), GetType(Short)}, Nothing)
        Console.WriteLine(MyMethod)
        ' Invoke MyMethod.
        myMethod.Invoke(myInstance, BindingFlags.InvokeMethod, New MyBinder(), New [Object]() {CInt(32), CInt(32)}, CultureInfo.CurrentCulture)
    End Sub
End Class

備註

這個方法會動態叫用這個實例在 上 obj反映的方法,並沿著指定的參數傳遞。 如果方法是靜態的,則會 obj 忽略 參數。 對於非靜態方法,應該是繼承或宣告方法之類別的實例, obj 而且類型必須與這個類別相同。 如果方法沒有參數,則的值 parameters 應該是 null。 否則,中的 parameters 元素數目、類型和順序應該與這個實例所反映之方法的參數數目、類型和順序相同。

您不可以省略 對 Invoke的呼叫中的選擇性參數。 若要叫用方法並省略選擇性參數,請改為呼叫 Type.InvokeMember

注意

如果使用這個方法多載來叫用實例建構函式,則會重新初始化提供給 obj 的物件;也就是說,會執行所有實例初始化表達式。 傳回值是 null。 如果叫用類別建構函式,則會重新初始化類別;也就是說,會執行所有類別初始化表達式。 傳回值是 null

針對傳值基本參數,會執行一般擴展 (Int16 -> Int32,例如) 。 對於傳值參考參數,允許 (衍生類別為基類,而基類為介面類型) 。 不過,針對傳址傳遞基本參數,類型必須完全相符。 針對傳址參考參數,一般擴展仍適用。

例如,如果這個實例所反映的方法宣告為 public boolean Compare(String a, String b),則 parameters 應該是長度為 2 的 Objects 陣列,如此一來 parameters[0] = new Object("SomeString1") and parameters[1] = new Object("SomeString2")

如果目前方法的參數是實值型別,而 中的 parameters 對應自變數為 null,則運行時間會傳遞實值型別的零初始化實例。

反映會在叫用虛擬方法時使用動態方法查閱。 例如,假設類別 B 繼承自類別 A,並同時實作名為 M 的虛擬方法。現在假設您有代表 MethodInfo 類別 A 上 M 的物件。如果您使用 Invoke 方法在類型 B 的物件上叫用 M,則反映會使用類別 B 所提供的實作。即使類型 B 的物件轉換成 A,仍會使用類別 B 所提供的實作, (請參閱下列程式碼範例) 。

另一方面,如果方法為非虛擬,則反映會使用從中 MethodInfo 取得的型別所提供的實作,而不論傳遞為目標的物件類型為何。

完全信任的程式代碼會忽略存取限制。 也就是說,每當程式代碼完全信任時,都可以透過反映來存取和叫用私人建構函式、方法、字段和屬性。

如果叫用的方法擲回例外狀況,此方法 Exception.GetBaseException 會傳回原始例外狀況。

注意

從 .NET Framework 2.0 開始,如果呼叫端已使用 旗標授ReflectionPermissionReflectionPermissionFlag.RestrictedMemberAccess與呼叫端,而且非公用成員的授與集限制為呼叫端的授與集,或是子集,則這個方法可用來存取非公用成員。 (請參閱 Reflection.) 若要使用這項功能的安全性考慮,您的應用程式應以 .NET Framework 3.5 或更新版本為目標。

另請參閱

適用於