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

July 28, 2014

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

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

public ConstructorInfo GetConstructor(
	BindingFlags bindingAttr,
	Binder binder,
	Type[] types,
	ParameterModifier[] modifiers
)

Parameters

bindingAttr
Type: System.Reflection.BindingFlags
A bitmask comprised of one or more BindingFlags that specify how the search is conducted.
-or-
Zero, to return null.
binder
Type: System.Reflection.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
Type: System.Type []
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
Type: System.Reflection.ParameterModifier []
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

Type: System.Reflection.ConstructorInfo
A ConstructorInfo object representing the constructor that matches the specified requirements, if found; otherwise, null.

ExceptionCondition
ArgumentNullException

types is null.

-or-

One of the elements in types is null.

ArgumentException

types is multidimensional.

-or-

modifiers is multidimensional.

-or-

types and modifiers do not have the same length.

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 null 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.

To get the class initializer (.cctor) using this method overload, you must specify BindingFlags.Static | BindingFlags.NonPublic (BindingFlags.StaticOrBindingFlags.NonPublic in Visual Basic).

NoteNote:

You cannot omit parameters when looking up constructors and methods. You can only omit parameters when invoking.

If the current Type represents a constructed generic type, this method returns the ConstructorInfo with the type parameters replaced by the appropriate type arguments. If the current Type represents a type parameter in the definition of a generic type or generic method, this method always returns null.

Version Notes

Windows Phone

 GetConstructor throws an ArgumentNullException exception when modifiers is null.

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.


using System;
using System.Reflection;
using System.Security;

public class Example
{
    public Example(int i){}
    public static void Demo(System.Windows.Controls.TextBlock outputBlock)
    {
        try
        {
            Type  myType = typeof(Example);
            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, types, null);
            if(constructorInfoObj != null)
            {
                outputBlock.Text += "The constructor of Example that is a public " +
                    "instance method and takes an integer as a parameter is: " + Environment.NewLine;
                outputBlock.Text += constructorInfoObj.ToString() + Environment.NewLine;
            }
            else
            {
                outputBlock.Text += "The constructor of Example that is a public instance " +
                    "method and takes an integer as a parameter is not available." + Environment.NewLine;
            }
        }
        catch(ArgumentNullException e)
        {
            outputBlock.Text += "ArgumentNullException: " + e.Message + Environment.NewLine;
        }
        catch(ArgumentException e)
        {
            outputBlock.Text += "ArgumentException: " + e.Message + Environment.NewLine;
        }
        catch(SecurityException e)
        {
            outputBlock.Text += "SecurityException: " + e.Message + Environment.NewLine;
        }
        catch(Exception e)
        {
            outputBlock.Text += "Exception: " + e.Message + Environment.NewLine;
        }
    }
}


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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