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Type.GetConstructor Method (BindingFlags, Binder, CallingConventions, Type[], ParameterModifier[])

.NET Framework 1.1

Searches for a constructor whose parameters match the specified argument types and modifiers, using the specified binding constraints and the specified calling convention.

[Visual Basic]
Overloads Public Function GetConstructor( _
   ByVal bindingAttr As BindingFlags, _
   ByVal binder As Binder, _
   ByVal callConvention As CallingConventions, _
   ByVal types() As Type, _
   ByVal modifiers() As ParameterModifier _
) As ConstructorInfo
[C#]
public ConstructorInfo GetConstructor(
 BindingFlags bindingAttr,
 Binder binder,
 CallingConventions callConvention,
 Type[] types,
 ParameterModifier[] modifiers
);
[C++]
public: ConstructorInfo* GetConstructor(
 BindingFlags bindingAttr,
 Binder* binder,
 CallingConventions callConvention,
 Type* types[],
 ParameterModifier modifiers[]
);
[JScript]
public function GetConstructor(
   bindingAttr : BindingFlags,
 binder : Binder,
 callConvention : CallingConventions,
 types : Type[],
 modifiers : ParameterModifier[]
) : ConstructorInfo;

Parameters

bindingAttr
A bitmask comprised of one or more BindingFlags that specify how the search is conducted.

-or-

Zero, to return a null reference (Nothing in Visual Basic).

binder
A Binder object that defines a set of properties and enables binding, which can involve selection of an overloaded method, coercion of argument types, and invocation of a member through reflection.

-or-

A null reference (Nothing in Visual Basic), to use the DefaultBinder.

callConvention
The CallingConventions object that specifies the set of rules to use regarding the order and layout of arguments, how the return value is passed, what registers are used for arguments, and the stack is cleaned up.
types
An array of Type objects representing the number, order, and type of the parameters for the constructor to get.

-or-

An empty array of the type Type (that is, Type[] types = new Type[0]) to get a constructor that takes no parameters.

modifiers
An array of ParameterModifier objects representing the attributes associated with the corresponding element in the types array. The default binder does not process this parameter.

Return Value

A ConstructorInfo object representing the constructor that matches the specified requirements, if found; otherwise, a null reference (Nothing in Visual Basic).

Exceptions

Exception Type Condition
ArgumentNullException types is a null reference (Nothing in Visual Basic).

-or-

One of the elements in types is a null reference (Nothing).

ArgumentException types is multidimensional.

-or-

modifiers is multidimensional.

-or-

types and modifiers do not have the same length.

Remarks

Although the default binder does not process ParameterModifier (the modifiers parameter), you can use the abstract System.Reflection.Binder class to write a custom binder that does process modifiers. ParameterModifier is only used when calling through COM interop, and only parameters that are passed by reference are handled.

The types array and the modifiers array have the same length. A parameter specified in the types array can have the following attributes, which are specified in the modifiers array: pdIn, pdOut, pdLcid, pdRetval, pdOptional, and pdHasDefault, which represent [In], [Out], [lcid], [retval], [optional], and a value specifying whether the parameter has a default value. A parameter's associated attributes are stored in the metadata and enhance interoperability.

If an exact match does not exist, the binder will attempt to coerce the parameter types specified in the types array in order to select a match. If the binder is unable to select a match, then a null reference (Nothing in Visual Basic) is returned.

The following BindingFlags filter flags can be used to define which constructors to include in the search:

  • You must specify either BindingFlags.Instance or BindingFlags.Static in order to get a return.
  • Specify BindingFlags.Public to include public constructors in the search.
  • Specify BindingFlags.NonPublic to include non-public constructors (that is, private and protected constructors) in the search.

See System.Reflection.BindingFlags for more information.

GetConstructor cannot be used to obtain a class initializer. Class initializers are available through GetMember, GetMembers, FindMembers, GetConstructors, and TypeInitializer.

If the requested constructor is non-public and the caller does not have ReflectionPermission to reflect non-public methods outside the current assembly, this method returns a null reference (Nothing).

The following table shows what members of a base class are returned by the Get methods when reflecting on a type.

Member Type Static Non-Static
Constructor No No
Field No Yes. A field is always hide-by-name-and-signature.
Event Not applicable The common type system rule is that the inheritance is the same as that of the methods that implement the property. Reflection treats properties as hide-by-name-and-signature. See note 2 below.
Method No Yes. A method (both virtual and non-virtual) can be hide-by-name or hide-by-name-and-signature.
Nested Type No No
Property Not applicable The common type system rule is that the inheritance is the same as that of the methods that implement the property. Reflection treats properties as hide-by-name-and-signature. See note 2 below.
  1. Hide-by-name-and-signature considers all of the parts of the signature, including custom modifiers, return types, parameter types, sentinels, and unmanaged calling conventions. This is a binary comparison.
  2. For reflection, properties and events are hide-by-name-and-signature. If you have a property with both a get and a set accessor in the base class, but the derived class has only a get accessor, the derived class property hides the base class property, and you will not be able to access the setter on the base class.
  3. Custom attributes are not part of the common type system.
Note   You cannot omit parameters when looking up constructors and methods. You can only omit parameters when invoking.

Example

[Visual Basic, C#, C++] The following example obtains the type of MyClass1, gets the ConstructorInfo object that matches the specified binding flags, and displays the constructor signature.

[Visual Basic] 
Public Class MyClass1
    Public Sub New(ByVal i As Integer)
    End Sub
    Public Shared Sub Main()
        Try
            Dim myType As Type = GetType(MyClass1)
            Dim types(0) As Type
            types(0) = GetType(Integer)
            ' Get the public instance constructor that takes an integer parameter.
            Dim constructorInfoObj As ConstructorInfo = _
                        myType.GetConstructor(BindingFlags.Instance Or _
                        BindingFlags.Public, Nothing, _
                        CallingConventions.HasThis, types, Nothing)
            If Not (constructorInfoObj Is Nothing) Then
                Console.WriteLine("The constructor of MyClass1 that " + _
                                  "is a public instance method and takes an " + _
                                  "integer as a parameter is: ")
                Console.WriteLine(constructorInfoObj.ToString())
            Else
                Console.WriteLine("The constructor MyClass1 that " + _
                                  "is a public instance method and takes an " + _
                                  "integer as a parameter is not available.")
            End If
        Catch e As ArgumentNullException
            Console.WriteLine("ArgumentNullException: " + e.Message)
        Catch e As ArgumentException
            Console.WriteLine("ArgumentException: " + e.Message)
        Catch e As SecurityException
            Console.WriteLine("SecurityException: " + e.Message)
        Catch e As Exception
            Console.WriteLine("Exception: " + e.Message)
        End Try
    End Sub
End Class

[C#] 
using System;
using System.Reflection;
using System.Security;

public class MyClass1
{
    public MyClass1(int i){}
    public static void Main()
    {
        try
        {
            Type  myType = typeof(MyClass1);
            Type[] types = new Type[1];
            types[0] = typeof(int);
            // Get the public instance constructor that takes an integer parameter.
            ConstructorInfo constructorInfoObj = myType.GetConstructor(
                BindingFlags.Instance | BindingFlags.Public, null,
                CallingConventions.HasThis, types, null);
            if(constructorInfoObj != null)
            {
                Console.WriteLine("The constructor of MyClass1 that is a public " +
                    "instance method and takes an integer as a parameter is: ");
                Console.WriteLine(constructorInfoObj.ToString());
            }
            else
            {
                Console.WriteLine("The constructor of MyClass1 that is a public instance " +
                    "method and takes an integer as a parameter is not available.");
            }
        }
        catch(ArgumentNullException e)
        {
            Console.WriteLine("ArgumentNullException: " + e.Message);
        }
        catch(ArgumentException e)
        {
            Console.WriteLine("ArgumentException: " + e.Message);
        }
        catch(SecurityException e)
        {
            Console.WriteLine("SecurityException: " + e.Message);
        }
        catch(Exception e)
        {
            Console.WriteLine("Exception: " + e.Message);
        }
    }
}

[C++] 
#using <mscorlib.dll>

using namespace System;
using namespace System::Reflection;
using namespace System::Security;

public __gc class MyClass1 {
public:
   MyClass1(int i) {}
}
;
int main() {
   try {
      Type*  myType = __typeof(MyClass1);
      Type* types[] = new Type*[1];
      types->Item[0] = __typeof(int);
      // Get the public instance constructor that takes an integer parameter.
      ConstructorInfo*  constructorInfoObj = myType->GetConstructor(static_cast<BindingFlags>(BindingFlags::Instance | BindingFlags::Public), 0,
         CallingConventions::HasThis, types, 0);
      if (constructorInfoObj != 0) {
         Console::WriteLine(S"The constructor of MyClass1 that is a public instance method and takes an integer as a parameter is: ");
         Console::WriteLine(constructorInfoObj);
      } else {
         Console::WriteLine(S"The constructor of MyClass1 that is a public instance method and takes an integer as a parameter is not available.");
      }
   } catch (ArgumentNullException* e) {
      Console::WriteLine(S"ArgumentNullException: {0}", e->Message);
   } catch (ArgumentException* e) {
      Console::WriteLine(S"ArgumentException: {0}", e->Message);
   } catch (SecurityException* e) {
      Console::WriteLine(S"SecurityException: {0}", e->Message);
   } catch (Exception* e) {
      Console::WriteLine(S"Exception: {0}", e->Message);
   }
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

.NET Framework Security: 

See Also

Type Class | Type Members | System Namespace | Type.GetConstructor Overload List | ConstructorInfo | BindingFlags | Binder | DefaultBinder | CallingConventions | ParameterModifier | ReflectionPermission | GetConstructorImpl | GetConstructors

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