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MethodBase.Invoke Method (Object, Object[])

Updated: January 2010

Invokes the method or constructor represented by the current instance, using the specified parameters.

Namespace:  System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

public Object Invoke(
	Object obj,
	Object[] parameters
)

Parameters

obj
Type: System.Object

The object on which to invoke the method or constructor. If a method is static, this argument is ignored. If a constructor is static, this argument must be null or an instance of the class that defines the constructor.

parameters
Type: System.Object[]

An argument list for the invoked method or constructor. This is an array of objects with the same number, order, and type as the parameters of the method or constructor to be invoked. If there are no parameters, parameters should be null.

If the method or constructor represented by this instance takes a ref parameter (ByRef in Visual Basic), no special attribute is required for that parameter in order to invoke the method or constructor using this function. Any object in this array that is not explicitly initialized with a value will contain the default value for that object type. For reference-type elements, this value is null. For value-type elements, this value is 0, 0.0, or false, depending on the specific element type.

Return Value

Type: System.Object
An object containing the return value of the invoked method, or null in the case of a constructor.

Implements

_MethodBase.Invoke(Object, Object[])

ExceptionCondition
TargetException

The obj parameter is null and the method is not static.

-or-

The method is not declared or inherited by the class of obj.

-or-

A static constructor is invoked, and obj is neither null nor an instance of the class that declared the constructor.

ArgumentException

The elements of the parameters array do not match the signature of the method or constructor reflected by this instance.

TargetInvocationException

The invoked method or constructor throws an exception.

TargetParameterCountException

The parameters array does not have the correct number of arguments.

MethodAccessException

The caller does not have permission to execute the constructor.

InvalidOperationException

The type that declares the method is an open generic type. That is, the Type.ContainsGenericParameters property returns true for the declaring type.

NotSupportedException

The current MethodBase is a MethodBuilder.

This is a convenience method that calls the Invoke(Object, BindingFlags, Binder, Object[], CultureInfo) method overload, passing Default for invokeAttr and null for binder and culture.

If the invoked method throws an exception, the Exception.GetBaseException method returns the exception.

To invoke a static method using its MethodInfo object, pass null for obj.

NoteNote:

If this method overload is used to invoke an instance constructor, the object supplied for obj is reinitialized; that is, all instance initializers are executed. The return value is null. If a class constructor is invoked, the class is reinitialized; that is, all class initializers are executed. The return value is null.

NoteNote:

Starting with the .NET Framework version 2.0 Service Pack 1, this method can be used to access non-public members if the caller has been granted ReflectionPermission with the ReflectionPermissionFlag.RestrictedMemberAccess flag and if the grant set of the non-public members is restricted to the caller’s grant set, or a subset thereof. (See Security Considerations for Reflection.)

To use this functionality, your application should target the .NET Framework version 3.5. For more information, see .NET Framework 3.5 Architecture.

If a parameter of the current method is a value type, and the corresponding argument in parameters is null, the runtime passes a zero-initialized instance of the value type.

The following code example demonstrates dynamic method lookup using reflection. Note that you cannot use the MethodInfo object from the base class to invoke the overridden method in the derived class, because late binding cannot resolve overrides.

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

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

January 2010

Clarified the behavior when null is passed for a value type.

Content bug fix.

October 2009

Noted that this method overload throws a NotSupportedException for the derived class MethodBuilder.

Content bug fix.

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