C#Assembly中的CreateInstance和Activator 中的CreateInstance
Assembly中的CreateInstance,使用区分大小写的搜索,从此程序集中查找指定的类型,然后使用系统激活器创建它的实例。它最后调用的是Activator中的CreateInstance方法。
[Serializable]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(_Assembly))]
[ComVisible(true)]
[__DynamicallyInvokable]
[PermissionSet(SecurityAction.InheritanceDemand, Unrestricted = true)]
public abstract class Assembly : _Assembly, IEvidenceFactory, ICustomAttributeProvider, ISerializable
{
public object CreateInstance(string typeName)
{
return CreateInstance(typeName, ignoreCase: false, BindingFlags.Instance | BindingFlags.Public, null, null, null, null);
}
public virtual object CreateInstance(string typeName, bool ignoreCase, BindingFlags bindingAttr, Binder binder, object[] args, CultureInfo culture, object[] activationAttributes)
{
Type type = GetType(typeName, throwOnError: false, ignoreCase);
if (type == null)
{
return null;
}
return Activator.CreateInstance(type, bindingAttr, binder, args, culture, activationAttributes);
}
}
Activator 中的CreateInstance。
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(_Activator))]
[ComVisible(true)]
[__DynamicallyInvokable]
public sealed class Activator : _Activator
{
[MethodImpl(MethodImplOptions.NoInlining)]
[SecuritySafeCritical]
public static object CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, object[] args, CultureInfo culture, object[] activationAttributes)
{
if ((object)type == null)
{
throw new ArgumentNullException("type");
}
if (type is TypeBuilder)
{
throw new NotSupportedException(Environment.GetResourceString("NotSupported_CreateInstanceWithTypeBuilder"));
}
if ((bindingAttr & (BindingFlags)255) == 0)
{
bindingAttr |= BindingFlags.Instance | BindingFlags.Public | BindingFlags.CreateInstance;
}
if (activationAttributes != null && activationAttributes.Length != 0)
{
if (!type.IsMarshalByRef)
{
throw new NotSupportedException(Environment.GetResourceString("NotSupported_ActivAttrOnNonMBR"));
}
if (!type.IsContextful && (activationAttributes.Length > 1 || !(activationAttributes[0] is UrlAttribute)))
{
throw new NotSupportedException(Environment.GetResourceString("NotSupported_NonUrlAttrOnMBR"));
}
}
RuntimeType runtimeType = type.UnderlyingSystemType as RuntimeType;
if (runtimeType == null)
{
throw new ArgumentException(Environment.GetResourceString("Arg_MustBeType"), "type");
}
StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
return runtimeType.CreateInstanceImpl(bindingAttr, binder, args, culture, activationAttributes, ref stackMark);
}
}
示例:
以下示例定义类 Person
并调用 CreateInstance(String) 方法来实例化它。
using System;
using System.Reflection;
using Contoso.Libraries;
namespace Contoso.Libraries
{
public class Person
{
private string _name;
public Person()
{ }
public Person(string name)
{
this._name = name;
}
public string Name
{ get { return this._name; }
set { this._name = value; } }
public override string ToString()
{
return this._name;
}
}
}
public class Example
{
public static void Main()
{
Assembly assem = typeof(Person).Assembly;
Person p = (Person) assem.CreateInstance("Contoso.Libraries.Person");
if (! (p == null)) {
p.Name = "John";
Console.WriteLine("Instantiated a {0} object whose value is '{1}'",
p.GetType().Name, p);
}
else {
Console.WriteLine("Unable to instantiate a Person object.");
}
}
}
// The example displays the following output:
// Instantiated a Person object whose value is 'John'
原文地址:https://blog.csdn.net/huaqianzkh/article/details/140701343
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