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在运行时创建表示 F# 记录或联合的 System.Type 实例的最佳方法是什么？也就是说，我正在为记录和联合寻找等效的 FSharpType.MakeTupleType。

澄清一下，我对创建实例（即 FSharpValue.MakeRecord 或 FSharpValue.MakeUnion）不感兴趣。

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我不知道F# 库中的记录和联合的FSharpType.MakeTupleType等效项。

在运行时创建类似记录或联合类型的结构的一种方法是使用Reflection.Emit。记录类型类似于密封类，联合类型是抽象基类，每种情况都有密封类。

例如，以下函数生成最小 F# 记录类型：

open System
open System.Reflection
open System.Reflection.Emit

let MakeRecord(typeName:string, fields:(string * Type)[]) =
    let name = "GeneratedAssembly"
    let domain = AppDomain.CurrentDomain
    let assembly = domain.DefineDynamicAssembly(AssemblyName(name), AssemblyBuilderAccess.RunAndSave)
    let name = "GeneratedModule"
    let dm = assembly.DefineDynamicModule(name, name+".dll")
    let attributes = TypeAttributes.Public ||| TypeAttributes.Class ||| TypeAttributes.Sealed
    let typeBuilder = dm.DefineType(typeName, attributes)
    let con = typeof<CompilationMappingAttribute>.GetConstructor([|typeof<SourceConstructFlags>|])
    let customBuilder = CustomAttributeBuilder(con, [|SourceConstructFlags.RecordType|])
    typeBuilder.SetCustomAttribute(customBuilder)
    let makeField name t =
        let attributes = FieldAttributes.Assembly
        let fieldBuilder = typeBuilder.DefineField(name+"@", t, attributes)
        let attributes = PropertyAttributes.None
        let propertyBuilder = typeBuilder.DefineProperty(name, attributes, t, [||])
        let customBuilder = CustomAttributeBuilder(con, [|SourceConstructFlags.Field|])
        propertyBuilder.SetCustomAttribute(customBuilder)
        let attributes = MethodAttributes.Public ||| MethodAttributes.HideBySig ||| MethodAttributes.SpecialName
        let methodBuilder = typeBuilder.DefineMethod("get_"+name, attributes, t, [||])
        let il = methodBuilder.GetILGenerator()
        il.Emit(OpCodes.Ldarg_0)
        il.Emit(OpCodes.Ldfld, fieldBuilder)
        il.Emit(OpCodes.Ret)
        propertyBuilder.SetGetMethod(methodBuilder)
        fieldBuilder
    let types = fields |> Array.map snd
    let cb = typeBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, types)
    let il = cb.GetILGenerator()
    il.Emit(OpCodes.Ldarg_0)
    il.Emit(OpCodes.Call, typeof<obj>.GetConstructor(Type.EmptyTypes))
    fields |> Array.iteri (fun i (name, t) -> 
        let paramName = name.Substring(0,1).ToLower()+name.Substring(1)
        let param = cb.DefineParameter(i+1, ParameterAttributes.In, paramName)
        let fieldBuilder = makeField name t
        il.Emit(OpCodes.Ldarg_0)
        il.Emit(OpCodes.Ldarg, param.Position)
        il.Emit(OpCodes.Stfld, fieldBuilder)
    )
    il.Emit(OpCodes.Ret)
    let t = typeBuilder.CreateType()
    assembly.Save("GeneratedModule.dll")
    t

let r = MakeRecord("MyRecord", [|"Alpha",typeof<int>;"Beta",typeof<string>|])

请注意，可能还需要生成 Record 类型的预期接口，即缺少 IEquatable、IStructuralEquatable、IComparable 和 IStructuralComparable 的实现。

更新

基于上述代码示例的扩展方法 MakeTupleType 和 MakeUnionType 现在可在开源Fil（F# 到 IL 编译器）项目（alpha）中使用。

于 2013-04-22T07:41:13.920 回答