dictionary - 如何从 FSharp 中的反射调用 Map.Add？

Question

鉴于 FSI 中的以下代码:

type Mapping = Map<int,string>

let mm = [ for i in Assembly.GetAssembly(typeof<Mapping>).ExportedTypes do yield i]|> List.find(fun m -> m.Name.Contains("MapModule"))
let mt = mm.GetMethod("Empty", BindingFlags.Static ||| BindingFlags.Public)
let mymap = mt.MakeGenericMethod([|typeof<string>; typeof<string>|]).Invoke(null, [||])

let addmethod = typeof<Mapping>.GetMethod("Add")

addmethod.Invoke(mymap, [|box(1);box("astring")|])

最后一行产生此错误:

System.Reflection.TargetException: Object does not match target type. at System.Reflection.RuntimeMethodInfo.CheckConsistency(Object target) at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters) at .$FSI_0006.main@() Stopped due to error

即使您切换 int 和 string 参数，也会出现此错误。

有趣的是，下面的代码可以工作:

type Mapping = Map<string,string>

let mm = [ for i in Assembly.GetAssembly(typeof<Mapping>).ExportedTypes do yield i]|> List.find(fun m -> m.Name.Contains("MapModule"))
let mt = mm.GetMethod("Empty", BindingFlags.Static ||| BindingFlags.Public)
let mymap = mt.MakeGenericMethod([|typeof<string>; typeof<string>|]).Invoke(null, [||])

let addmethod = typeof<Mapping>.GetMethod("Add")
addmethod.Invoke(mymap, [|box("a");box("b")|])

那么如何从反射中有效地调用 Map.Add 呢？

Answer 1

找到了。

这一行:

let mymap = mt.MakeGenericMethod([|typeof<string>; typeof<string>|]).Invoke(null, [||])

应该是:

let mymap = mt.MakeGenericMethod([|typeof<int>; typeof<string>|]).Invoke(null, [||])

类型不匹配实际上是真实的，因为使用不正确的泛型类型调用了“Empty”方法。

所以这最终是正确的代码:

type Mapping = Map<int,string>

let mm = [ for i in Assembly.GetAssembly(typeof<Mapping>).ExportedTypes do yield i]|> List.find(fun m -> m.Name.Contains("MapModule"))
let mt = mm.GetMethod("Empty", BindingFlags.Static ||| BindingFlags.Public)
let am = mm.GetMethod("Add", BindingFlags.Static ||| BindingFlags.Public)
let mymap = mt.MakeGenericMethod([|typeof<int>; typeof<string>|]).Invoke(null, [||])
let addmethod = typeof<Mapping>.GetMethod("Add")

addmethod.Invoke(mymap, [|box(1);box("astring")|])