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

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

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

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.

-or-

EmptyTypes.

modifiers

An array of ParameterModifier objects representing the attributes associated with the corresponding element in the parameter type 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

Remarks

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.

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 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.

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 program obtains the type of MyClass1 class, gets the ConstructorInfo object matching the specified binding flags, and displays the signature of the constructor.

[Visual Basic] 
Imports System
Imports System.Reflection
Imports System.Security


Public Class MyClass1
    Public Sub New(ByVal i As Integer)
    End Sub 'New

    Public Shared Sub Main()
        Try
            Dim myType As Type = GetType(MyClass1)
            Dim types(0) As Type
            types(0) = GetType(Integer)
            ' Get the constructor that is public and takes an integer parameter.
            Dim constructorInfoObj As ConstructorInfo = _
                     myType.GetConstructor(BindingFlags.Instance Or _
                     BindingFlags.Public, Nothing, types, Nothing)
            If Not (constructorInfoObj Is Nothing) Then
                Console.WriteLine("The constructor of MyClass1 that is " + _
                               "public and takes an integer as a parameter is ")
                Console.WriteLine(constructorInfoObj.ToString())
            Else
                Console.WriteLine("The constructor of MyClass1 that is " + _
                  "public 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 constructor that is public and takes an integer parameter.
            ConstructorInfo constructorInfoObj = myType.GetConstructor(
                BindingFlags.Instance | BindingFlags.Public, null, types, null);
            if (constructorInfoObj != null )
            {
                Console.WriteLine("The constructor of MyClass1 that is public " +
                    "and takes an integer as a parameter is:");
                Console.WriteLine(constructorInfoObj.ToString());
            }
            else
            {
                Console.WriteLine("The constructor of the MyClass1 that is public " +
                    "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 constructor that is public and takes an integer parameter.
      ConstructorInfo*  constructorInfoObj = myType->GetConstructor(static_cast<BindingFlags>(BindingFlags::Instance | BindingFlags::Public), 0, types, 0);
      if (constructorInfoObj != 0) {
         Console::WriteLine(S"The constructor of MyClass1 that is public and takes an integer as a parameter is:");
         Console::WriteLine(constructorInfoObj);
      } else {
         Console::WriteLine(S"The constructor of the MyClass1 that is public 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 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 Compact Framework, Common Language Infrastructure (CLI) Standard

.NET Framework Security: 

• ReflectionPermission for reflecting non-public methods. Associated enumeration: ReflectionPermissionFlag.TypeInformation

See Also

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