Type.GetConstructor Method

Definition

Gets a specific constructor of the current Type.

Overloads

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

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

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

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

GetConstructor(BindingFlags, Type[])

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

GetConstructor(Type[])

Searches for a public instance constructor whose parameters match the types in the specified array.

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

Source:
Type.cs
Source:
Type.cs
Source:
Type.cs

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

public System.Reflection.ConstructorInfo? GetConstructor (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder? binder, System.Reflection.CallingConventions callConvention, Type[] types, System.Reflection.ParameterModifier[]? modifiers);
public System.Reflection.ConstructorInfo GetConstructor (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, System.Reflection.CallingConventions callConvention, Type[] types, System.Reflection.ParameterModifier[] modifiers);
[System.Runtime.InteropServices.ComVisible(true)]
public System.Reflection.ConstructorInfo GetConstructor (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, System.Reflection.CallingConventions callConvention, Type[] types, System.Reflection.ParameterModifier[] modifiers);

Parameters

bindingAttr
BindingFlags

A bitwise combination of the enumeration values that specify how the search is conducted.

-or-

Default to return null.

binder
Binder

An 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
CallingConventions

The 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
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.

modifiers
ParameterModifier[]

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.

Returns

An object representing the constructor that matches the specified requirements, if found; otherwise, null.

Implements

Attributes

Exceptions

types is null.

-or-

One of the elements in types is null.

types is multidimensional.

-or-

modifiers is multidimensional.

-or-

types and modifiers do not have the same length.

Examples

The following example obtains the type of MyClass, gets the ConstructorInfo object, and displays the constructor signature.

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

public class MyClass3
{
    public MyClass3(int i) { }
    public static void Main()
    {
        try
        {
            Type myType = typeof(MyClass3);
            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 MyClass3 that is a public " +
                    "instance method and takes an integer as a parameter is: ");
                Console.WriteLine(constructorInfoObj.ToString());
            }
            else
            {
                Console.WriteLine("The constructor of MyClass3 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);
        }
    }
}

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.

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, internal, and protected constructors) in the search.

See System.Reflection.BindingFlags for more information.

To get the class initializer (static constructor) using this method, you must specify BindingFlags.Static | BindingFlags.NonPublic (BindingFlags.StaticOrBindingFlags.NonPublic in Visual Basic). You can also get the class initializer using the TypeInitializer property.

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.

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.

See also

Applies to

.NET 9 and other versions
Product Versions
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1

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

Source:
Type.cs
Source:
Type.cs
Source:
Type.cs

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

public System.Reflection.ConstructorInfo? GetConstructor (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder? binder, Type[] types, System.Reflection.ParameterModifier[]? modifiers);
public System.Reflection.ConstructorInfo GetConstructor (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, Type[] types, System.Reflection.ParameterModifier[] modifiers);
[System.Runtime.InteropServices.ComVisible(true)]
public System.Reflection.ConstructorInfo GetConstructor (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, Type[] types, System.Reflection.ParameterModifier[] modifiers);

Parameters

bindingAttr
BindingFlags

A bitwise combination of the enumeration values that specify how the search is conducted.

-or-

Default to return null.

binder
Binder

An 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[]

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
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.

Returns

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

Implements

Attributes

Exceptions

types is null.

-or-

One of the elements in types is null.

types is multidimensional.

-or-

modifiers is multidimensional.

-or-

types and modifiers do not have the same length.

Examples

The following example obtains the type of MyClass, gets the ConstructorInfo object, and displays the constructor signature.

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

public class MyClass2
{
    public MyClass2(int i) { }
    public static void Main()
    {
        try
        {
            Type myType = typeof(MyClass2);
            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 MyClass2 that is public " +
                    "and takes an integer as a parameter is:");
                Console.WriteLine(constructorInfoObj.ToString());
            }
            else
            {
                Console.WriteLine("The constructor of the MyClass2 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);
        }
    }
}

Remarks

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, internal, and protected constructors) in the search.

See System.Reflection.BindingFlags for more information.

To get the class initializer (static constructor) using this method overload, you must specify BindingFlags.Static | BindingFlags.NonPublic (BindingFlags.StaticOrBindingFlags.NonPublic in Visual Basic). You can also get the class initializer using the TypeInitializer property.

Note

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.

See also

Applies to

.NET 9 and other versions
Product Versions
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1

GetConstructor(BindingFlags, Type[])

Source:
Type.cs
Source:
Type.cs
Source:
Type.cs

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

public System.Reflection.ConstructorInfo? GetConstructor (System.Reflection.BindingFlags bindingAttr, Type[] types);

Parameters

bindingAttr
BindingFlags

A bitwise combination of the enumeration values that specify how the search is conducted. -or- Default to return null.

types
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 = Array.Empty{Type}()) to get a constructor that takes no parameters. -or- EmptyTypes.

Returns

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

Applies to

.NET 9 and other versions
Product Versions
.NET 6, 7, 8, 9

GetConstructor(Type[])

Source:
Type.cs
Source:
Type.cs
Source:
Type.cs

Searches for a public instance constructor whose parameters match the types in the specified array.

public System.Reflection.ConstructorInfo? GetConstructor (Type[] types);
public System.Reflection.ConstructorInfo GetConstructor (Type[] types);
[System.Runtime.InteropServices.ComVisible(true)]
public System.Reflection.ConstructorInfo GetConstructor (Type[] types);

Parameters

types
Type[]

An array of Type objects representing the number, order, and type of the parameters for the desired constructor.

-or-

An empty array of Type objects, to get a constructor that takes no parameters. Such an empty array is provided by the static field EmptyTypes.

Returns

An object representing the public instance constructor whose parameters match the types in the parameter type array, if found; otherwise, null.

Implements

Attributes

Exceptions

types is null.

-or-

One of the elements in types is null.

types is multidimensional.

Examples

The following example obtains the type of MyClass, gets the ConstructorInfo object, and displays the constructor signature.

using System;
using System.Reflection;

public class MyClass1
{
    public 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 takes an integer as a parameter.
            ConstructorInfo constructorInfoObj = myType.GetConstructor(types);
            if (constructorInfoObj != null)
            {
                Console.WriteLine("The constructor of MyClass1 that takes an " +
                    "integer as a parameter is: ");
                Console.WriteLine(constructorInfoObj.ToString());
            }
            else
            {
                Console.WriteLine("The constructor of MyClass1 that takes an integer " +
                    "as a parameter is not available.");
            }
        }
        catch (Exception e)
        {
            Console.WriteLine("Exception caught.");
            Console.WriteLine("Source: " + e.Source);
            Console.WriteLine("Message: " + e.Message);
        }
    }
}

Remarks

This method overload looks for public instance constructors and cannot be used to obtain a class initializer (static constructor). To get a class initializer, use an overload that takes BindingFlags, and specify BindingFlags.Static | BindingFlags.NonPublic (BindingFlags.StaticOrBindingFlags.NonPublic in Visual Basic). You can also get the class initializer using the TypeInitializer property.

If the requested constructor is non-public, this method returns null.

Note

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.

See also

Applies to

.NET 9 and other versions
Product Versions
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1