c# - 无法将 FileStream 隐式转换为 Json 文件的 StreamWriter

Question

所以，我正在阅读一本关于 .NET Core 3 的书，并且我正在学习如何序列化 JSON 文件的部分。我遇到了我无法找到解决方案的类型的问题。我尝试过解决它，但后来我遇到了其他类型的问题。我在下面的代码中遇到的问题是 Main at 的最后一个 using 语句中的 CS0029 File.Create(jsonPath)：

无法将类型“System.IO.FileStream”隐式转换为“System.IO.StreamWriter”

根据我从 Microsoft 文档中获得的示例，我尝试将 using 语句更改为使用 FileStream 类型而不是 StreamWriter，但这会在 jsonStream 变量的jsonSerializer.Serialize(jsonStream, people)行中产生错误：

无法从“System.IO.FileStream”转换为“System.IO.TextWriter”

下面是代码：

using System;
using System.Collections.Generic;
using System.Xml.Serialization;
using System.IO;
using Packt.Shared;
using static System.Console;
using static System.Environment;
using static System.IO.Path;

namespace WorkingWithSerialization
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Person> people = new List<Person>
            {
                new Person(30000M)
                {
                    FirstName = "Adam",
                    LastName = "Smith",
                    DateOfBirth = new DateTime(1756,12,12)
                },
                new Person(40000M)
                {
                    FirstName = "Lisa",
                    LastName = "Simpson",
                    DateOfBirth = new DateTime(1980,4,30)
                },
                new Person(20000M)
                {
                    FirstName = "Barney",
                    LastName = "Rubble",
                    DateOfBirth = new DateTime(1962,7,14),
                    Children = new HashSet<Person>
                    {
                        new Person(0M)
                        {
                            FirstName = "Bob",
                            LastName = "Rubble",
                            DateOfBirth = new DateTime(1986,5,3)
                        },
                        new Person(0M)
                        {
                            FirstName = "Bamm-Bamm",
                            LastName = "Rubble",
                            DateOfBirth = new DateTime(1984,3,15)
                        }
                    }
                }
            };

            XmlSerializer xmlSerializer = new XmlSerializer(typeof(List<Person>));
            string path = Combine(CurrentDirectory, "people.xml");
            using(FileStream stream = File.Create(path))
            {
                xmlSerializer.Serialize(stream,people);
            }
            WriteLine($"Wrote {new FileInfo(path).Length} bytes to {path}.");
            WriteLine($"\n{File.ReadAllText(path)}");

            using(FileStream xmlLoad = File.Open(path, FileMode.Open))
            {
                List<Person> loadedPeople = (List<Person>)xmlSerializer.Deserialize(xmlLoad);
                foreach(Person person in loadedPeople)
                {
                    WriteLine($"{person.FirstName} has {person.Children.Count} children.");
                }
            }

            string jsonPath = Combine(CurrentDirectory, "people.json");
            using(StreamWriter jsonStream = File.Create(jsonPath))
            {
                var jsonSerializer = new Newtonsoft.Json.JsonSerializer();
                jsonSerializer.Serialize(jsonStream, people);
            }
        }
    }
}

我还在 .csproj 文件中包含了最新版本的 Newtonsoft.Json，但我认为这不是问题所在。

我也尝试了不同的铸造方式，但没有积极的结果。我不确定我做错了什么。

标签： c#.net-core

Answer 1

您需要一个额外的步骤来创建一个StreamWriter使用FileStream.

string jsonPath = Combine(CurrentDirectory, "people.json");
using (FileStream fs = File.Create(jsonPath))
using (StreamWriter jsonStream = new StreamWriter(fs))
{
    var jsonSerializer = new Newtonsoft.Json.JsonSerializer();
    jsonSerializer.Serialize(jsonStream, people);
}

如果我创建一个最小的 Person 类以便能够编译您的代码，我会得到一个如下所示的 json 文件：

[{
        "FirstName": "Adam",
        "LastName": "Smith",
        "DateOfBirth": "1756-12-12T00:00:00",
        "Children": null
    }, {
        "FirstName": "Lisa",
        "LastName": "Simpson",
        "DateOfBirth": "1980-04-30T00:00:00",
        "Children": null
    }, {
        "FirstName": "Barney",
        "LastName": "Rubble",
        "DateOfBirth": "1962-07-14T00:00:00",
        "Children": [{
                "FirstName": "Bob",
                "LastName": "Rubble",
                "DateOfBirth": "1986-05-03T00:00:00",
                "Children": null
            }, {
                "FirstName": "Bamm-Bamm",
                "LastName": "Rubble",
                "DateOfBirth": "1984-03-15T00:00:00",
                "Children": null
            }
        ]
    }
]