MSIL实用指南-创建字段

本篇讲解怎么创建字段，主要是在修饰符的创建上。

创建字段的方法是TypeBuilder.DefineField，传入字段名称、字段类型、字段修饰符等参数，返回一个FieldBuilder对象。
先看这一句程序

FieldBuilder nameFieldBuilder = typeBuilder.DefineField("Name", typeof(string), FieldAttributes.Private);

上面一条程序是创建一个叫"Name"的数据类型为"string"的字段，等同于

private string Name;

FieldAttributes是枚举类型，决定字段的修饰符。详细说明如下

C#语言规范只是用到了FieldAttributes的一部分枚举，并没有用到全部。

FieldBuilder ageFieldBuilder = typeBuilder.DefineField("Arg", typeof(int), FieldAttributes.Public);

等同于C#语言
public int Arg;

FieldBuilder maxCountFieldBuilder = typeBuilder.DefineField("MaxCount", typeof(long), FieldAttributes.Family);

等同于C#语言
protected long MaxCount;

FieldBuilder IFFieldBuilder = typeBuilder.DefineField("IF", typeof(string), FieldAttributes.Assembly);

等同于C#语言
internal string IF;

FieldBuilder PIFFieldBuilder = typeBuilder.DefineField("PIF", typeof(string),
FieldAttributes.Family | FieldAttributes.FamORAssem);

等同于C#语言
protected internal string PIF;

FieldBuilder PRFieldBuilder = typeBuilder.DefineField("RF", typeof(string),
FieldAttributes.Private | FieldAttributes.InitOnly);

等同于C#语言
private readonly string RF;

FieldBuilder CFFieldBuilder = typeBuilder.DefineField("CF", typeof(string),
FieldAttributes.Private | FieldAttributes.Literal);

等同于C#语言
private const string CF;

FieldBuilder SFFieldBuilder = typeBuilder.DefineField("SF", typeof(string),
FieldAttributes.Private | FieldAttributes.Static);

等同于C#语言
private static string SF;

完成的程序如下：

using System;
using System.Reflection;
using System.Reflection.Emit;

namespace LX1_ILDemo
{
    class Demo05_FieldCreate
    {
        static string binaryName = "Demo05_FieldCreate.dll";
        static string namespaceName = "LX1_ILDemo";
        static string typeName = "EmitFieldCreate";

        static AssemblyBuilder assemblyBuilder;
        static ModuleBuilder moduleBuilder;
        static TypeBuilder typeBuilder;

        static void Create_Fileds()
        {
            /* private string Name; */
            FieldBuilder nameFieldBuilder = typeBuilder.DefineField("Name", typeof(string), FieldAttributes.Private);
            /* public int Arg; */
            FieldBuilder ageFieldBuilder = typeBuilder.DefineField("Arg", typeof(int), FieldAttributes.Public);
            /* protected long MaxCount; */
            FieldBuilder maxCountFieldBuilder = typeBuilder.DefineField("MaxCount", typeof(long), FieldAttributes.Family);

            /* internal string IF; */
            FieldBuilder IFFieldBuilder = typeBuilder.DefineField("IF", typeof(string), FieldAttributes.Assembly);

            /* protected internal string PIF; */
            FieldBuilder PIFFieldBuilder = typeBuilder.DefineField("PIF", typeof(string),
                FieldAttributes.Family | FieldAttributes.FamORAssem);

            /* private readonly string RF; */
            FieldBuilder PRFieldBuilder = typeBuilder.DefineField("RF", typeof(string),
                FieldAttributes.Private | FieldAttributes.InitOnly);

            /* private const string CF; */
            FieldBuilder CFFieldBuilder = typeBuilder.DefineField("CF", typeof(string),
                FieldAttributes.Private | FieldAttributes.Literal);

            /* private static string SF; */
            FieldBuilder SFFieldBuilder = typeBuilder.DefineField("SF", typeof(string),
                FieldAttributes.Private | FieldAttributes.Static);
        }

        public static void Generate()
        {
            InitAssembly();

            typeBuilder = moduleBuilder.DefineType(namespaceName + "." + typeName, TypeAttributes.Public);
            Create_Fileds();

            SaveAssembly();
            Console.WriteLine("生成成功");
        }

        static void InitAssembly()
        {
            AssemblyName assemblyName = new AssemblyName(namespaceName);
            assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.RunAndSave);
            moduleBuilder = assemblyBuilder.DefineDynamicModule(assemblyName.Name, binaryName);
        }

        static void SaveAssembly()
        {
            Type t = typeBuilder.CreateType(); //完成Type，这是必须的
            assemblyBuilder.Save(binaryName);
        }
    }
}