C# 序列化和反序列化字符

我有一张我班上的角色名单。序列化和反序列化按预期工作。如果我的列表包含需要描述字节顺序标记的字符。示例字符代码是56256。所以，创建了一个简单的测试，如下所示

[Test]
public void Utf8CharSerializeAndDeserializeShouldEqual()
{
    UInt16 charCode = 56256;
    char utfChar = (char)charCode;
    using (MemoryStream ms = new MemoryStream())
    {
        using (StreamWriter writer = new StreamWriter(ms, Encoding.UTF8, 1024, true))
        {
            var serializer = new JsonSerializer();
            serializer.Serialize(writer, utfChar);
        }

        ms.Position = 0;
        using (StreamReader reader = new StreamReader(ms, true))
        {
            using (JsonTextReader jsonReader = new JsonTextReader(reader))
            { 
                var serializer = new JsonSerializer();
                char deserializedChar = serializer.Deserialize<char>(jsonReader);

                Console.WriteLine($"{(int)utfChar}, {(int)deserializedChar}");
                Assert.AreEqual(utfChar, deserializedChar);
                Assert.AreEqual((int)utfChar, (int)deserializedChar);
            }
        }
    }
}

---

当BOM表中不需要字符代码时，测试工作正常。例如，65A将通过此测试。

您的问题与Json.NET无关。您的问题是，这是一个无效的unicode字符，并且，如中所述，StreamWriter使用的Encoding.UTF8不会对此类字符进行编码：

Encoding.UTF8返回一个UTF8Encoding对象，该对象使用替换回退将无法编码的每个字符串和无法解码的每个字节替换为问号？性格

为了确认这一点，如果在测试示例中将Encoding.UTF8替换为，您将得到以下异常：

EncoderFallbackException: Unable to translate Unicode character \uDBC0 at index 1 to specified code page. 

如果要尝试序列化无效的Unicode字符值，则需要使用以下命令手动将其编码为字节数组：

public static partial class TextExtensions
{
    static void ToBytesWithoutEncoding(char c, out byte lower, out byte upper)
    {
        var u = (uint)c;
        lower = unchecked((byte)u);
        upper = unchecked((byte)(u >> 8));
    }

    public static byte[] ToByteArrayWithoutEncoding(this char c)
    {
        byte lower, upper;
        ToBytesWithoutEncoding(c, out lower, out upper);
        return new byte[] { lower, upper };
    }

    public static byte[] ToByteArrayWithoutEncoding(this ICollection<char> list)
    {
        if (list == null)
            return null;
        var bytes = new byte[checked(list.Count * 2)];
        int to = 0;
        foreach (var c in list)
        {
            ToBytesWithoutEncoding(c, out bytes[to], out bytes[to + 1]);
            to += 2;
        }
        return bytes;
    }

    public static char ToCharWithoutEncoding(this byte[] bytes)
    {
        return bytes.ToCharWithoutEncoding(0);
    }

    public static char ToCharWithoutEncoding(this byte[] bytes, int position)
    {
        if (bytes == null)
            return default(char);
        char c = default(char);
        if (position < bytes.Length)
            c += (char)bytes[position];
        if (position + 1 < bytes.Length)
            c += (char)((uint)bytes[position + 1] << 8);
        return c;
    }

    public static List<char> ToCharListWithoutEncoding(this byte[] bytes)
    {
        if (bytes == null)
            return null;
        var chars = new List<char>(bytes.Length / 2 + bytes.Length % 2);
        for (int from = 0; from < bytes.Length; from += 2)
        {
            chars.Add(bytes.ToCharWithoutEncoding(from));
        }
        return chars;
    }
}

然后按如下方式修改您的测试方法：

    public void Utf8JsonCharSerializeAndDeserializeShouldEqualFixed()
    {
        Utf8JsonCharSerializeAndDeserializeShouldEqualFixed((char)56256);
    }

    public void Utf8JsonCharSerializeAndDeserializeShouldEqualFixed(char utfChar)
    {
        byte[] data;

        using (MemoryStream ms = new MemoryStream())
        {
            using (StreamWriter writer = new StreamWriter(ms, new UTF8Encoding(true, true), 1024))
            {
                var serializer = new JsonSerializer();
                serializer.Serialize(writer, utfChar.ToByteArrayWithoutEncoding());
            }
            data = ms.ToArray();
        }

        using (MemoryStream ms = new MemoryStream(data))
        {
            using (StreamReader reader = new StreamReader(ms, true))
            {
                using (JsonTextReader jsonReader = new JsonTextReader(reader))
                {
                    var serializer = new JsonSerializer();
                    char deserializedChar = serializer.Deserialize<byte[]>(jsonReader).ToCharWithoutEncoding();

                    //Console.WriteLine(string.Format("{0}, {1}", utfChar, deserializedChar));
                    Assert.AreEqual(utfChar, deserializedChar);
                    Assert.AreEqual((int)utfChar, (int)deserializedChar);
                }
            }
        }
    }

public class RootObject
{
    [JsonConverter(typeof(CharListConverter))]
    public List<char> Characters { get; set; }
}

或者，如果某些容器类中有List属性，则可以创建以下转换器：

public class CharListConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(List<char>);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return null;
        var bytes = serializer.Deserialize<byte[]>(reader);
        return bytes.ToCharListWithoutEncoding();
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var list = (ICollection<char>)value;
        var bytes = list.ToByteArrayWithoutEncoding();
        serializer.Serialize(writer, bytes);
    }
}

并按如下方式应用：

    public void Utf8JsonCharSerializeAndDeserializeShouldEqualFixed()
    {
        Utf8JsonCharSerializeAndDeserializeShouldEqualFixed((char)56256);
    }

    public void Utf8JsonCharSerializeAndDeserializeShouldEqualFixed(char utfChar)
    {
        byte[] data;

        using (MemoryStream ms = new MemoryStream())
        {
            using (StreamWriter writer = new StreamWriter(ms, new UTF8Encoding(true, true), 1024))
            {
                var serializer = new JsonSerializer();
                serializer.Serialize(writer, utfChar.ToByteArrayWithoutEncoding());
            }
            data = ms.ToArray();
        }

        using (MemoryStream ms = new MemoryStream(data))
        {
            using (StreamReader reader = new StreamReader(ms, true))
            {
                using (JsonTextReader jsonReader = new JsonTextReader(reader))
                {
                    var serializer = new JsonSerializer();
                    char deserializedChar = serializer.Deserialize<byte[]>(jsonReader).ToCharWithoutEncoding();

                    //Console.WriteLine(string.Format("{0}, {1}", utfChar, deserializedChar));
                    Assert.AreEqual(utfChar, deserializedChar);
                    Assert.AreEqual((int)utfChar, (int)deserializedChar);
                }
            }
        }
    }

public class RootObject
{
    [JsonConverter(typeof(CharListConverter))]
    public List<char> Characters { get; set; }
}

---

在这两种情况下，Json.NET都会将字节数组编码为Base64。

您不能使用StreamWriter编写任意代码点，BOM表当然非常特殊。比如说，写一个代孕妈妈也没什么不同。如果您必须使用StreamWriter编写json，为什么？？然后至少做一个实验，看看json序列化程序是如何保存其安全性的，我们的api支持流写入，但我们已经对代码进行了一些修改。Json.net支持StreamWriter。我有一个字符列表，序列化的字符不等于反序列化的字符。这不是一个重要的问题吗？我不确定你说的是需要描述字节顺序标记还是不需要BOM。代码点56256也称为U+DBC0，是一个高代理代码点；它与字节顺序标记没有任何关系。