C#:额外知识点

 7、Const 与 Readonly 区别: 前者静态,后者动态; 前者值替换,后者可以在初始化时赋值

  编译结束之后使用Reflector或者IL工具查看代码,是没有I这个常量的,所有使用I这个常量的地方,都被替换成了值100。
基于以上原因,所有public修饰的变量,都不应该使用const修饰,因为,如果外部类引用了这个变量(常量),编译的时候,编译器会自动将该常量替换为值。后果就是,如果改变了该常量的值,就必须重新编译所有引用该常量的代码。
场景:该常量放在一个dll里,现在值变了,就必须更新所有引用了该dll的文件,而不是替换该dll就可以。

6、写入、输出二进制数据(指定地址 与 内存交互数据)

 public void WriteSerialize(object data, int offset, int length)
        {
            BinaryFormatter formatter = new BinaryFormatter();
            byte[] buffer = new byte[length];
            MemoryStream serializationStream = new MemoryStream(buffer, 0, length, true, true);
            formatter.Serialize(serializationStream, data);
            serializationStream.Flush();
            serializationStream.Close();
            this.WriteBytes(buffer, offset);
        }

 public void WriteBytes(byte[] data, int offset)
        {
            for (int i = 0; i < data.Length; i++)
            {
                Marshal.WriteByte(this.mappedView, offset + i, data[i]);
            }
        }

public object ReadDeserialize(int offset, int length)
        {
            byte[] data = new byte[length];
            this.ReadBytes(data, offset);
            BinaryFormatter formatter = new BinaryFormatter();
            MemoryStream serializationStream = new MemoryStream(data, 0, length, true, true);
            object obj2 = formatter.Deserialize(serializationStream);
            serializationStream.Close();
            return obj2;
        }

public void ReadBytes(byte[] data, int offset)
        {
            for (int i = 0; i < data.Length; i++)
            {
                data[i] = Marshal.ReadByte(this.mappedView, offset + i);
            }
        }
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5、设置、获取域值:

 public static void SetDomainValue(string key, object password)
        {
            AppDomain.CurrentDomain.SetData(key, password);
        }

        public static T GetDomainValue<T>(string key)
        { 
            object value=AppDomain.CurrentDomain.GetData(key) ;
            if(value==null)return default(T);
            return (T)value;
        }
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4、依据类型名称创建委托并执行

public delegate object MethodInvoker();

        public delegate Object ParamsConstructorDelegate(params object[] parameters);

        public static object NewInstance(Type type)
        {
            return CreateDelegate(type.GetConstructor(Type.EmptyTypes)).Invoke();
        }

        private static MethodInvoker CreateDelegate(ConstructorInfo target)
        {
            var dynamic = new DynamicMethod(string.Empty,
                typeof (object),
                new Type[0],
                target.DeclaringType);
            ILGenerator il = dynamic.GetILGenerator();
            il.DeclareLocal(target.DeclaringType);
            il.Emit(OpCodes.Newobj, target);
            il.Emit(OpCodes.Stloc_0);
            il.Emit(OpCodes.Ldloc_0);
            il.Emit(OpCodes.Ret);

            return (MethodInvoker) dynamic.CreateDelegate(typeof (MethodInvoker));
        }


        public static object NewInstance(Type type, params object[] parameters)
        {
            return BuildParamterConstructorDelegate(type).Invoke(parameters);
        }

        private static ParamsConstructorDelegate BuildParamterConstructorDelegate(Type type)
        {
            var mthd = new DynamicMethod(".ctor", type,
                new[] {typeof (object[])});
            ILGenerator il = mthd.GetILGenerator();
            ConstructorInfo ctor = type.GetConstructors()[0]; // not very robust, but meh...
            ParameterInfo[] ctorParams = ctor.GetParameters();
            for (int i = 0; i < ctorParams.Length; i++)
            {
                il.Emit(OpCodes.Ldarg_0);
                switch (i)
                {
                    case 0:
                        il.Emit(OpCodes.Ldc_I4_0);
                        break;
                    case 1:
                        il.Emit(OpCodes.Ldc_I4_1);
                        break;
                    case 2:
                        il.Emit(OpCodes.Ldc_I4_2);
                        break;
                    case 3:
                        il.Emit(OpCodes.Ldc_I4_3);
                        break;
                    case 4:
                        il.Emit(OpCodes.Ldc_I4_4);
                        break;
                    case 5:
                        il.Emit(OpCodes.Ldc_I4_5);
                        break;
                    case 6:
                        il.Emit(OpCodes.Ldc_I4_6);
                        break;
                    case 7:
                        il.Emit(OpCodes.Ldc_I4_7);
                        break;
                    case 8:
                        il.Emit(OpCodes.Ldc_I4_8);
                        break;
                    default:
                        il.Emit(OpCodes.Ldc_I4, i);
                        break;
                }
                il.Emit(OpCodes.Ldelem_Ref);
                Type paramType = ctorParams[i].ParameterType;
                il.Emit(paramType.IsValueType
                    ? OpCodes.Unbox_Any
                    : OpCodes.Castclass, paramType);
            }
            il.Emit(OpCodes.Newobj, ctor);
            il.Emit(OpCodes.Ret);
            return (ParamsConstructorDelegate)
                mthd.CreateDelegate(typeof (ParamsConstructorDelegate));
        }
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 依据反射创建实例:

        private static void InitUCBookCommonDll()
        {
            string dllItem = "My.Common";
            Assembly assembly = null;
            try
            {
                assembly = Assembly.Load(dllItem);
            }
            catch (Exception)
            {
                PrintLog(string.Format("加载程序集-{0}错误!", dllItem));
            }
            int index = dllItem.IndexOf("My");
            if (index != -1)
            {
                string typeName = dllItem.Substring(index) + ".LibLoader";
                Type type = assembly.GetType(typeName);
                if (type != null)
                    FastActivator.NewInstance(type);
            }
        }
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3、注册、发送Windows消息:

[DllImport("user32", SetLastError = true)]
        public static extern int RegisterWindowMessage(string message);
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  [DllImport("user32", SetLastError = true)]
        private static extern bool PostMessage(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam);
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2、通过类型名称、方法名称,执行方法:

        public static void MethodInvoker(object obj, string methodName, params object[] args)
        {
            Type type = obj.GetType();
            MethodInfo methodInfo = type.GetMethod(methodName);
            methodInfo.Invoke(obj, args);
        }
View Code

1、通过类型名称,创建实例:

public static object CreateInstance(string typeFullName, params object[] args)
        {
            Type type = Type.GetType(typeFullName);
            return Activator.CreateInstance(type, args);
        }
View Code

 

posted @ 2016-12-23 14:18  慧由心生  阅读(265)  评论(0编辑  收藏  举报