最近学习C#基础，简单记录一下C#中如何使用反射创建对象，并调用方法。

使用反射必须添加System.Reflection引用。

加载方式1：dll文件名，不需要扩展名

Assembly assembly = Assembly.Load("DB.MySql");

加载方式二：必须提供全部路径

Assembly assembly = Assembly.LoadFile(@"D:\Program\2022\TestCore\DB.MySql\bin\Debug\net6.0\DB.MySql.dll");

加载方式三：最常用

Assembly assembly = Assembly.LoadFrom(@"D:\Program\2022\TestCore\DB.MySql\bin\Debug\net6.0\DB.MySql.dll");
Assembly assembly = Assembly.LoadFrom("DB.MySql.dll");

Assembly assembly = Assembly.LoadFrom("DB.MySql.dll");
Type type = assembly.GetType("DB.MySql.MySqlHelper");//获取类型,必须是完整类型名称
object oDbHelper = Activator.CreateInstance(type);//创建实例
IDBHelper dbHelper = oDbHelper as IDBHelper;//as是类型转换，as转换不报错，类型不对就返回null
dbHelper.Query();

类代码如下：

namespace DB.MySql
{
    public class MySqlHelper : IDBHelper
    {
        public MySqlHelper() {
            Console.WriteLine($"{this.GetType().Name}被构造。");
        }
        public void Query()
        {
            Console.WriteLine($"{this.GetType().Name}.Query()执行");
        }
    }
}

Assembly assembly = Assembly.LoadFrom("DB.MySql.dll");
Type type = assembly.GetType("DB.MySql.TestClass");
object testClass=Activator.CreateInstance(type);//无参数构造函数
object testClass2 = Activator.CreateInstance(type,new object[]{"Ant编程"});
object testClass3 = Activator.CreateInstance(type, new object[] { 123 });
object testClass4 = Activator.CreateInstance(type, new object[] { 123, "1234" });

类代码如下：

namespace DB.MySql
{
    public class TestClass
    {
        public TestClass() {
            Console.WriteLine($"这是{this.GetType()}无参构造方法");
        }
        public TestClass(string name)
        {
            Console.WriteLine($"这是{this.GetType()}有参构造方法，类型为{name.GetType()}");
        }
        public TestClass(int id)
        {
            Console.WriteLine($"这是{this.GetType()}有参构造方法，类型为{id.GetType()}");
        }
        public TestClass(int id,string name)
        {
            Console.WriteLine($"这是{this.GetType()}有参构造方法，类型为{id.GetType()}和{name.GetType()}");
        }
    }
}

Assembly assembly = Assembly.LoadFrom("DB.MySql.dll");
Type type = assembly.GetType("DB.MySql.PrivateCtor");
object privateCtor = Activator.CreateInstance(type,true);

类代码如下：

namespace DB.MySql
{
    public class PrivateCtor
    {
        private PrivateCtor() {
            Console.WriteLine("对象创建成功！");
        }
    }
}

Assembly assembly = Assembly.LoadFrom("DB.MySql.dll");
Type type = assembly.GetType("DB.MySql.GenericClass`3");
Type makeType = type.MakeGenericType(new Type[] { typeof(int), typeof(string), typeof(string) });
object privateCtor = Activator.CreateInstance(makeType);

类代码如下：

namespace DB.MySql
{
    internal class GenericClass<T,W,S>
    {
    }
}