修改JSON输出

Question

我有一个Web方法返回一个List<AttributeCollection>。显然，AttributeCollection是一个包含每个属性值的属性列表(在本例中是由CRM2011SDK获取的)。

下面是该方法返回的JSON：

[
    [
        {
            "Key": "mobilephone",
            "Value": "(430) 565-1212"
        },
        {
            "Key": "firstname",
            "Value": "John"
        }
    ],
    [
        {
            "Key": "mobilephone",
            "Value": "(430) 565-1313"
        },
        {
            "Key": "firstname",
            "Value": "Mark"
        }
    ]
]

现在，第一对括号是列表的可视化表示，然后每个AttributeCollection都有许多对括号(AttributeCollection)。

我想去掉第一对括号，将其替换为顶级元素名(即：allAttributes)，然后是下面的所有项。

我对JsonMediaTypeFormatter的JsonMediaTypeFormatter方法做了过多的研究

public override System.Threading.Tasks.Task WriteToStreamAsync(Type type, object value, System.IO.Stream writeStream, HttpContent content, TransportContext transportContext)
{
    if ((typeof(IEnumerable<AttributeCollection>).IsAssignableFrom(type)))
    {
        //anything I could do here ?
    }


    return base.WriteToStreamAsync(type, value, writeStream, content, transportContext);
        } 

我曾想过要操作JSON字符串本身，但从那里看，它似乎是不可访问的。

有什么想法吗？

谢谢。

Answer 1

如果要在格式化程序本身上执行此操作，则可能需要将包装代码写入writeStream，如下所示(在记事本中测试)：

public override async Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
{
    if ((typeof(IEnumerable<AttributeCollection>).IsAssignableFrom(type)))
    {
        var list = (IEnumerable<AttributeCollection>)value;
        byte[] headerBytes = Encoding.UTF8.GetBytes("{\"allAttributes\":");
        byte[] footerBytes = Encoding.UTF8.GetBytes("}");
        writeStream.Write(headerBytes, 0, headerBytes.Length);
        foreach (var item in list)
        {
            await base.WriteToStreamAsync(item.GetType(), item, writeStream, content, transportContext);
        }

        writeStream.Write(footerBytes, 0, footerBytes.Length);
    }
    else
    {
        return await base.WriteToStreamAsync(type, value, writeStream, content, transportContext);
    }
}

另一种选择是创建包装类并序列化它：

public class MyWrappingClass
{
    public IEnumerable<AttributeCollection> allAttributes { get; set; }
}

public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
{
    if ((typeof(IEnumerable<AttributeCollection>).IsAssignableFrom(type)))
    {
        var list = (IEnumerable<AttributeCollection>)value;
        var obj = new MyWrappingClass { allAttributes = list };
        return base.WriteToStreamAsync(obj.GetType(), obj, writeStream, content, transportContext);
    }
    else
    {
        return base.WriteToStreamAsync(type, value, writeStream, content, transportContext);
    }
}