我使用FluentValidation，我想用一些对象的属性值的格式的消息。现在的问题是我有在C＃中的前pressions和代表们非常缺乏经验。

I am using FluentValidation and I want to format a message with some of the object's properties value. The problem is I have very little experience with expressions and delegates in C#.

FluentValidation已经提供了一种与格式参数做到这一点。

FluentValidation already provides a way to do this with format arguments.

RuleFor(x => x.Name).NotEmpty()
    .WithMessage("The name {1} is not valid for Id {0}", x => x.Id, x => x.Name);

我愿做这样的事情，以避免更改消息字符串，如果我更改参数的顺序。

I would like to do something like this to avoid having to change the message string if I change the order of the parameters.

RuleFor(x => x.Name).NotEmpty()
    .WithMessage("The name {Name} is not valid for Id {Id}", 
    x => new
        {
            Id = x.Id,
            Name = x.Name
        });

原来的方法签名如下所示：

The original method signature looks like this:

public static IRuleBuilderOptions<T, TProperty> WithMessage<T, TProperty>(
    this IRuleBuilderOptions<T, TProperty> rule, string errorMessage, 
    params Func<T, object>[] funcs)

我在想提供这种方法与函数功能的列表。

I was thinking of providing this method with a list of Func.

任何人都可以帮助我？

推荐答案

您不能做到这一点，在FluentValidation的WithMessage但你可以高插孔CustomState财产和有注入你的消息。这里是一个工作的例子;你的另一个选择是到餐桌FluentValidation并进行额外的过载为WithMethod。

You can't do that with the WithMessage in FluentValidation but you can high-jack the CustomState property and inject your message there. Here is a working example; Your other option is to fork FluentValidation and make an additional overload for the WithMethod.

这是从这个博客帖子的控制台应用程序从的NuGet引用FluentValidation和JamesFormater：

This is a console application with references to FluentValidation from Nuget and the JamesFormater from this blog post:

http://haacked.com/archive/2009/01/04/fun-with-named-formats-string-parsing-and-edge-cases.aspx

的最佳答案。拿了灵感来自伊利亚，实现你可以捎带过一口流利验证的扩展方法本质。这样的在下面的工作原理，而不需要修改在库中的任何

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Web;
using System.Web.UI;
using FluentValidation;

namespace stackoverflow.fv
{
    class Program
    {
        static void Main(string[] args)
        {
            var target = new My() { Id = "1", Name = "" };
            var validator = new MyValidator();
            var result = validator.Validate(target);

            foreach (var error in result.Errors)
                Console.WriteLine(error.ErrorMessage);

            Console.ReadLine();
        }
    }

    public class MyValidator : AbstractValidator<My>
    {
        public MyValidator()
        {
            RuleFor(x => x.Name).NotEmpty().WithNamedMessage("The name {Name} is not valid for Id {Id}");
        }
    }

    public static class NamedMessageExtensions
    {
        public static IRuleBuilderOptions<T, TProperty> WithNamedMessage<T, TProperty>(
            this IRuleBuilderOptions<T, TProperty> rule, string format)
        {
            return rule.WithMessage("{0}", x => format.JamesFormat(x));
        }
    }

    public class My
    {
        public string Id { get; set; }
        public string Name { get; set; }
    }

    public static class JamesFormatter
    {
        public static string JamesFormat(this string format, object source)
        {
            return FormatWith(format, null, source);
        }

        public static string FormatWith(this string format
            , IFormatProvider provider, object source)
        {
            if (format == null)
                throw new ArgumentNullException("format");

            List<object> values = new List<object>();
            string rewrittenFormat = Regex.Replace(format,
              @"(?<start>\{)+(?<property>[\w\.\[\]]+)(?<format>:[^}]+)?(?<end>\})+",
              delegate(Match m)
              {
                  Group startGroup = m.Groups["start"];
                  Group propertyGroup = m.Groups["property"];
                  Group formatGroup = m.Groups["format"];
                  Group endGroup = m.Groups["end"];

                  values.Add((propertyGroup.Value == "0")
                    ? source
                    : Eval(source, propertyGroup.Value));

                  int openings = startGroup.Captures.Count;
                  int closings = endGroup.Captures.Count;

                  return openings > closings || openings % 2 == 0
                     ? m.Value
                     : new string('{', openings) + (values.Count - 1)
                       + formatGroup.Value
                       + new string('}', closings);
              },
              RegexOptions.Compiled
              | RegexOptions.CultureInvariant
              | RegexOptions.IgnoreCase);

            return string.Format(provider, rewrittenFormat, values.ToArray());
        }

        private static object Eval(object source, string expression)
        {
            try
            {
                return DataBinder.Eval(source, expression);
            }
            catch (HttpException e)
            {
                throw new FormatException(null, e);
            }
        }
    }
}