JsonReader.ReadRawValue在哪里？

问题描述

我正在实现自定义JsonConverter。

在WriteJson的实现中，我使用函数JsonWriter.WriteRawValue()编写对象。

在实现ReadJson时，我想以自己的方式读取和管理相同的值，我希望找到函数JsonReader.ReadRawValue()，但它不存在。

我想念什么吗？

谢谢

解决方法

我自己解决了。

在我看来，我是第一个需要此功能的人。

您可以在下面看到ReadJson的实现以及支持读取字段原始值的功能。

尽管如此，我还是针对相当复杂的数据结构测试了代码，但我不能声称它涵盖了任何可能的用例。

    public override YourCustomType ReadJson(JsonReader reader,Type objectType,YourCustomType existingValue,bool hasExistingValue,JsonSerializer serializer)
    {
        // read the value of my field as a JObject
        JObject someJsonValue = (JObject)serializer.Deserialize(reader,typeof(object));
        
        // get the raw-value from the JObject
        string rawValue = ReadAnyRawValue(someJsonValue);
        
        // do whatever processing with the raw-value
        YourCustomType returnObj; // create the return object
        return returnObj;
    }

    // It returns the raw-value of the passed-in token. 
    // The passed-in token must NOT be of type Property. 
    // The token can be any Json value(if it's a Json value means it's not a Property).
    // Depending on the data-type of the value (of the token) the return value of this function can be: {...} or [...] or null or "some text" or any other primary data value
    private string ReadAnyRawValue(JToken anyValueToken)
    {
        // anyToken can be an object,it can be an array or it can be a primary value
        
        if(anyValueToken.Type == JTokenType.Property)
        {
            throw new ArgumentException($"The parameter {nameof(anyValueToken)} is not supposed to be of type JTokenType.Property. It must be a value.");
        }
        
        if(anyValueToken.Type == JTokenType.Object)
        {
            return ReadObjectRawValue(anyValueToken);
        }
        else if(anyValueToken.Type == JTokenType.Array)
        {
            return ReadArrayRawValue(anyValueToken);
        }
        else
        {
            // it's a primary value or null;
            
            if(anyValueToken.Type == JTokenType.Null)
            {
                return "null";
            }
            else if(anyValueToken.Type == JTokenType.String)
            {
                return @$"""{anyValueToken}""";
            }
            else
            {
                return @$"{anyValueToken}";
            }
        }
        
    }
    
    // It returns the property name and its raw-value in the format: "Name":RawValue
    // Depending on the data-type of the property,RawValue can be {...} or [...] or null or "some text" or any other primary data value
    // The passed-in token must be of type Property,that means an object that has a Name and a Value
    private string ReadPropertyRaw(JProperty jProp)
    {
        return @$"""{jProp.Name}"":{ReadAnyRawValue(jProp.Value)}";
    }
    
    // It returns a json object,that means {...}
    // The passed-in token must be of type Object
    private string ReadObjectRawValue(JToken objectToken)
    {
        if(objectToken.Type != JTokenType.Object)
        {
            throw new ArgumentException($"The parameter {nameof(objectToken)} is expected to be of type JTokenType.Object");
        }
        
        StringBuilder bld = new StringBuilder(500);
        bld.Append('{');
        
        JToken tmp = objectToken.First;

        bool isFirst = true;
        while (tmp != null)
        {
            
            if (!isFirst)
            {
                bld.Append(',');
            }

            if(tmp.Type == JTokenType.Property)
            {
                bld.Append(this.ReadPropertyRaw(tmp as JProperty));
            }
            else
            {
                bld.Append($"{tmp}");
            }
            tmp = tmp.Next;
            isFirst = false;
        }

        bld.Append('}');
        
        return bld.ToString();
    }
    
    // It returns a json array,that means: [...]
    // The passed-in token must be of type Array
    private string ReadArrayRawValue(JToken arrayToken)
    {
        if (arrayToken.Type != JTokenType.Array)
        {
            throw new ArgumentException($"The parameter {nameof(arrayToken)} is expected to be of type JTokenType.Array");
        }
        StringBuilder bld = new StringBuilder(500);
        bld.Append('[');
        var tmp = arrayToken.First;

        bool isFirst = true;
        while (tmp != null)
        {
            if (!isFirst)
            {
                bld.Append(',');
            }
            
            // the elements of an array always values (not properties)
            bld.Append(ReadAnyRawValue(tmp));
            
            tmp = tmp.Next;
            isFirst = false;
        }
        bld.Append(']');
        return bld.ToString();
    }