CSharpScript.EvaluateAsync 无法识别枚举

Question

我正在使用

CSharpScript.EvaluateAsync

从字符串生成谓词。使用字符串和 int 变量它工作正常但是如果我尝试在字符串中传递一个枚举变量来转换它会抛出错误：

消息“(1,26)：错误 CS0103：名称‘状态’在当前上下文中不存在”字符串

这是独立的复制品：

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.CodeAnalysis.CSharp.Scripting;
using Microsoft.CodeAnalysis.Scripting;

namespace PredicateParser
{
    class Program
    {
        static void Main(string[] args)
        {
            var albums = new List<Album>
            {
                new Album { Quantity = 10, Artist = "Betontod", Title = "Revolution", Status = Status.Offline},
                new Album { Quantity = 50, Artist = "The Dangerous Summer", Title = "The Dangerous Summer", Status = Status.Offline },
                new Album { Quantity = 200, Artist = "Depeche Mode", Title = "Spirit", Status = Status.Online },
            };


            var albumFilter1 = "album => album.Quantity > 20 && album.Quantity < 200"; //works fine
            var albumFilter2 = "album => album.Status == Status.Online"; //Throws exception

            var predicate1 = CreatePredicate<Album>(albumFilter1);
            var predicate2 = CreatePredicate<Album>(albumFilter2);

            var filteredAlbums1 = albums.Where(predicate1).ToList();
            var filteredAlbums2 = albums.Where(predicate2).ToList();

        }

        public static Func<T, bool> CreatePredicate<T>(string command)
        {
            var options = ScriptOptions.Default.AddReferences(typeof(T).Assembly);
            Func<T, bool> predicate = CSharpScript.EvaluateAsync<Func<T, bool>>(command, options).Result;

            return predicate;
        }

    }



    public class Album
    {
        public int Quantity { get; set; }
        public string Title { get; set; }
        public string Artist { get; set; }
        public Status Status { get; set; }
    }

    public enum Status
    {
        Online,
        Offline
    }
    
}

我怎样才能让它与枚举一起工作？

Answer 1

var options = ScriptOptions.Default.AddReferences(typeof(T).Assembly).AddImports(nameof(PredicateParser));

您忘记添加“使用命名空间”:)

Answer 2

在这种情况下，如果你用命名空间完全限定它就不会出错。

"album => album.Status == PredicateParser.Status.Online"

Answer 3

我在处理动态过滤功能（我必须为

.Where(...)

调用构建表达式）时收到此错误，而过滤属性是

Enum

类型。

我不得不改变我的lambda从

❌

"t => t.IntervalType == Enum.Parse<IntervalType>("Cron")"

到这里

✅

"t => t.IntervalType == System.Enum.Parse<TaskScheduler.Core.Models.IntervalType>("Cron")"

.

为了构建 lambda，我对这种形式的值使用字符串插值

❌

$"Enum.Parse<{t.Name}>(\"{value}\")"

必须更新为：

✅

$"System.Enum.Parse<{t.FullName}>(\"{value}\")"