小编典典

如何动态创建类?

c#

我有一堂课,看起来像这样:

public class Field
{
    public string FieldName;
    public string FieldType;
}

还有一个List<Field>带有值的对象:

{"EmployeeID","int"},
{"EmployeeName","String"},
{"Designation","String"}

我想创建一个看起来像这样的类:

Class DynamicClass
{
    int EmployeeID,
    String EmployeeName,
    String Designation
}

有什么办法吗?

我希望这在运行时生成。我不希望文件系统中存在物理CS文件。


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2020-05-19

共1个答案

小编典典

是的,您可以System.Reflection.Emit为此使用命名空间。如果您没有经验,这不是直截了当的,但肯定是可能的。

编辑: 此代码可能有缺陷,但是它将为您提供总体思路,并有望为实现该目标提供良好的开端。

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

namespace TypeBuilderNamespace
{
    public static class MyTypeBuilder
    {
        public static void CreateNewObject()
        {
            var myType = CompileResultType();
            var myObject = Activator.CreateInstance(myType);
        }
        public static Type CompileResultType()
        {
            TypeBuilder tb = GetTypeBuilder();
            ConstructorBuilder constructor = tb.DefineDefaultConstructor(MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.RTSpecialName);

            // NOTE: assuming your list contains Field objects with fields FieldName(string) and FieldType(Type)
            foreach (var field in yourListOfFields)
                CreateProperty(tb, field.FieldName, field.FieldType);

            Type objectType = tb.CreateType();
            return objectType;
        }

        private static TypeBuilder GetTypeBuilder()
        {
            var typeSignature = "MyDynamicType";
            var an = new AssemblyName(typeSignature);
            AssemblyBuilder assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(an, AssemblyBuilderAccess.Run);
            ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("MainModule");
            TypeBuilder tb = moduleBuilder.DefineType(typeSignature,
                    TypeAttributes.Public |
                    TypeAttributes.Class |
                    TypeAttributes.AutoClass |
                    TypeAttributes.AnsiClass |
                    TypeAttributes.BeforeFieldInit |
                    TypeAttributes.AutoLayout,
                    null);
            return tb;
        }

        private static void CreateProperty(TypeBuilder tb, string propertyName, Type propertyType)
        {
            FieldBuilder fieldBuilder = tb.DefineField("_" + propertyName, propertyType, FieldAttributes.Private);

            PropertyBuilder propertyBuilder = tb.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, null);
            MethodBuilder getPropMthdBldr = tb.DefineMethod("get_" + propertyName, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, propertyType, Type.EmptyTypes);
            ILGenerator getIl = getPropMthdBldr.GetILGenerator();

            getIl.Emit(OpCodes.Ldarg_0);
            getIl.Emit(OpCodes.Ldfld, fieldBuilder);
            getIl.Emit(OpCodes.Ret);

            MethodBuilder setPropMthdBldr =
                tb.DefineMethod("set_" + propertyName,
                  MethodAttributes.Public |
                  MethodAttributes.SpecialName |
                  MethodAttributes.HideBySig,
                  null, new[] { propertyType });

            ILGenerator setIl = setPropMthdBldr.GetILGenerator();
            Label modifyProperty = setIl.DefineLabel();
            Label exitSet = setIl.DefineLabel();

            setIl.MarkLabel(modifyProperty);
            setIl.Emit(OpCodes.Ldarg_0);
            setIl.Emit(OpCodes.Ldarg_1);
            setIl.Emit(OpCodes.Stfld, fieldBuilder);

            setIl.Emit(OpCodes.Nop);
            setIl.MarkLabel(exitSet);
            setIl.Emit(OpCodes.Ret);

            propertyBuilder.SetGetMethod(getPropMthdBldr);
            propertyBuilder.SetSetMethod(setPropMthdBldr);
        }
    }
}
2020-05-19