为什么默认的构造函数不显示此值类型？ [英] Why default constructor does not appear for value types?

问题描述

下面的代码片段给了我一个类型的构造函数和方法的列表。

The below snippet gives me a list of constructors and methods of a type.

static void ReflectOnType(Type type)
    {
        Console.WriteLine(type.FullName);
        Console.WriteLine("------------");
        List<ConstructorInfo> constructors =
            type.GetConstructors(BindingFlags.Public | BindingFlags.Static | BindingFlags.NonPublic |BindingFlags.Instance | BindingFlags.Default).ToList();

        List<MethodInfo> methods = type.GetMethods().ToList();

        Type baseType = type.BaseType;

        while (baseType != null)
        {
            constructors.AddRange(baseType.GetConstructors(BindingFlags.Public | BindingFlags.Static | BindingFlags.NonPublic |
                              BindingFlags.Instance | BindingFlags.Default));
            methods.AddRange(baseType.GetMethods());
            baseType = baseType.BaseType;
        }

        Console.WriteLine("Reflection on {0} type", type.Name);

        for (int i = 0; i < constructors.Count; i++)
        {
            Console.Write("Constructor: {0}.{1}", constructors[i].DeclaringType.Name, constructors[i].Name);
            Console.Write("(");
            ParameterInfo[] parameterInfos = constructors[i].GetParameters();
            if (parameterInfos.Length > 0)
            {
                for (int j = 0; j < parameterInfos.Length; j++)
                {
                    if (j > 0)
                    {
                        Console.Write(", ");
                    }
                    Console.Write("{0} {1}", parameterInfos[j].ParameterType, parameterInfos[j].Name);
                }
            }
            Console.Write(")");

            if (constructors[i].IsSpecialName)
            {
                Console.Write(" has 'SpecialName' attribute");
            }
            Console.WriteLine();
        }
        Console.WriteLine();

        for (int i = 0; i < methods.Count; i++)
        {
            Console.Write("Method: {0}.{1}", methods[i].DeclaringType.Name, methods[i].Name);
            // Determine whether or not each field is a special name.
            if (methods[i].IsSpecialName)
            {
                Console.Write(" has 'SpecialName' attribute");
            }
            Console.WriteLine();
        }
    }

但是当我通过一个'诠释'类型的这种方法，为什么不让我看到在输出中隐含的构造？或者说，我怎么修改上面的code列出了默认的构造函数，以及（在情况下，我失去了一些东西在我的code）。

But when I pass an ‘int’ type to this method, why don’t I see the implicit constructor in the output? Or, how do I modify the above code to list the default constructor as well (in case I’m missing something in my code).

推荐答案

在C＃（和大多数CLI语言） - 指定在一个结构参数的构造函数是被禁止的，因此，一个结构在C＃（和大多数其他创建的。 NET语言）甚至不会在IL中定义的参数的构造函数。在CLR始终使用定义的规则（基本上，填充零当量所有值）初始化值类型，和C＃强制执行，作为唯一的选择。

In C# (and most CLI languages) - specifying a parameterless constructor on a struct is forbidden, and as such, a struct created in C# (and most other .NET languages) will not even have a parameterless constructor defined in the IL. The CLR always initializes value types using defined rules (basically, filling all values with zero equivalents), and C# enforces that as the only option.

由于默认，参数的构造函数中不产生结构C＃的存在，它不使用反射时显示。

Since the default, parameterless constructor does not exist in a C# generated struct, it does not display when using reflection.

这篇关于为什么默认的构造函数不显示此值类型？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！