47

我试过：

  NameValueCollection Data = new NameValueCollection();
  Data.Add("foo","baa");
  string json = new JavaScriptSerializer().Serialize(Data);

它返回：["foo"]我期望{"foo" : "baa"} 我该怎么做？

4

4 回答 4

56

序列化 NameValueCollection 的一种方法是首先将其转换为 Dictionary，然后序列化 Dictionary。要转换为字典：

thenvc.AllKeys.ToDictionary(k => k, k => thenvc[k]);

如果需要经常进行转换，还可以为 NameValueCollection 创建一个扩展方法：

public static class NVCExtender
{
    public static IDictionary<string, string> ToDictionary(
                                        this NameValueCollection source)
    {
        return source.AllKeys.ToDictionary(k => k, k => source[k]);
    }
}

所以你可以像这样在一行中进行转换：

NameValueCollection Data = new NameValueCollection();
Data.Add("Foo", "baa");

var dict = Data.ToDictionary();

然后你可以序列化字典：

var json = new JavaScriptSerializer().Serialize(dict);
// you get {"Foo":"baa"}

但是 NameValueCollection 一个键可以有多个值，例如：

NameValueCollection Data = new NameValueCollection();
Data.Add("Foo", "baa");
Data.Add("Foo", "again?");

如果你序列化这个，你会得到{"Foo":"baa,again?"}.

您可以修改转换器以改为生成IDictionary<string, string[]>：

public static IDictionary<string, string[]> ToDictionary(
                                    this NameValueCollection source)
{
    return source.AllKeys.ToDictionary(k => k, k => source.GetValues(k));
}

所以你可以得到这样的序列化值：{"Foo":["baa","again?"]}.

于 2013-03-16T03:56:28.453 回答
40

NameValueCollection不是 IDictionary，因此JavaScriptSerializer无法按照您的预期直接对其进行序列化。您需要先将其转换为字典，然后对其进行序列化。

更新：以下关于每个键的多个值的问题，调用nvc[key]将简单地返回它们，用逗号分隔，这可能没问题。如果没有，人们总是可以调用GetValues并决定适当地处理这些值。更新了下面的代码以显示一种可能的方式。

public class StackOverflow_7003740
{
    static Dictionary<string, object> NvcToDictionary(NameValueCollection nvc, bool handleMultipleValuesPerKey)
    {
        var result = new Dictionary<string, object>();
        foreach (string key in nvc.Keys)
        {
            if (handleMultipleValuesPerKey)
            {
                string[] values = nvc.GetValues(key);
                if (values.Length == 1)
                {
                    result.Add(key, values[0]);
                }
                else
                {
                    result.Add(key, values);
                }
            }
            else
            {
                result.Add(key, nvc[key]);
            }
        }

        return result;
    }

    public static void Test()
    {
        NameValueCollection nvc = new NameValueCollection();
        nvc.Add("foo", "bar");
        nvc.Add("multiple", "first");
        nvc.Add("multiple", "second");

        foreach (var handleMultipleValuesPerKey in new bool[] { false, true })
        {
            if (handleMultipleValuesPerKey)
            {
                Console.WriteLine("Using special handling for multiple values per key");
            }
            var dict = NvcToDictionary(nvc, handleMultipleValuesPerKey);
            string json = new JavaScriptSerializer().Serialize(dict);
            Console.WriteLine(json);
            Console.WriteLine();
        }
    }
}
于 2011-08-09T22:27:24.100 回答
3

如果您的字典不打算包含许多条目，则可以使用该类： System.Collections.Specialized.ListDictionary

于 2011-11-22T11:15:15.920 回答
1

为了完整起见，并且因为问题继续被问到（例如这里），只要您使用 Json.NET 或DataContractJsonSerializer（但不是JavaScriptSerializer），您可以使用适配器模式并将其包装NameValueCollection在IDictionary<string, string[]>适配器中，然后使用任何完全支持序列化任意字典的序列化器。

一旦这样的适配器如下：

public class NameValueCollectionDictionaryAdapter<TNameValueCollection> : IDictionary<string, string[]>
    where TNameValueCollection : NameValueCollection, new()
{
    readonly TNameValueCollection collection;

    public NameValueCollectionDictionaryAdapter() : this(new TNameValueCollection()) { }

    public NameValueCollectionDictionaryAdapter(TNameValueCollection collection)
    {
        this.collection = collection;
    }

    // Method instead of a property to guarantee that nobody tries to serialize it.
    public TNameValueCollection GetCollection() { return collection; }

    #region IDictionary<string,string[]> Members

    public void Add(string key, string[] value)
    {
        if (collection.GetValues(key) != null)
            throw new ArgumentException("Duplicate key " + key);
        if (value == null)
            collection.Add(key, null);
        else
            foreach (var str in value)
                collection.Add(key, str);
    }

    public bool ContainsKey(string key) { return collection.GetValues(key) != null; }

    public ICollection<string> Keys { get { return collection.AllKeys; } }

    public bool Remove(string key)
    {
        bool found = ContainsKey(key);
        if (found)
            collection.Remove(key);
        return found;
    }

    public bool TryGetValue(string key, out string[] value)
    {
        return (value = collection.GetValues(key)) != null;
    }

    public ICollection<string[]> Values
    {
        get
        {
            return new ReadOnlyCollectionAdapter<KeyValuePair<string, string[]>, string[]>(this, p => p.Value);
        }
    }

    public string[] this[string key]
    {
        get
        {
            var value = collection.GetValues(key);
            if (value == null)
                throw new KeyNotFoundException(key);
            return value;
        }
        set
        {
            Remove(key);
            Add(key, value);
        }
    }

    #endregion

    #region ICollection<KeyValuePair<string,string[]>> Members

    public void Add(KeyValuePair<string, string[]> item) { Add(item.Key, item.Value); }

    public void Clear() { collection.Clear(); }

    public bool Contains(KeyValuePair<string, string[]> item)
    {
        string[] value;
        if (!TryGetValue(item.Key, out value))
            return false;
        return EqualityComparer<string[]>.Default.Equals(item.Value, value); // Consistent with Dictionary<TKey, TValue>
    }

    public void CopyTo(KeyValuePair<string, string[]>[] array, int arrayIndex)
    {
        foreach (var item in this)
            array[arrayIndex++] = item;
    }

    public int Count { get { return collection.Count; } }

    public bool IsReadOnly { get { return false; } }

    public bool Remove(KeyValuePair<string, string[]> item)
    {
        if (Contains(item))
            return Remove(item.Key);
        return false;
    }

    #endregion

    #region IEnumerable<KeyValuePair<string,string[]>> Members

    public IEnumerator<KeyValuePair<string, string[]>> GetEnumerator()
    {
        foreach (string key in collection)
            yield return new KeyValuePair<string, string[]>(key, collection.GetValues(key));
    }

    #endregion

    #region IEnumerable Members

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); }

    #endregion
}

public static class NameValueCollectionExtensions
{
    public static NameValueCollectionDictionaryAdapter<TNameValueCollection> ToDictionaryAdapter<TNameValueCollection>(this TNameValueCollection collection)
        where TNameValueCollection : NameValueCollection, new()
    {
        if (collection == null)
            throw new ArgumentNullException();
        return new NameValueCollectionDictionaryAdapter<TNameValueCollection>(collection);
    }
}

public class ReadOnlyCollectionAdapter<TIn, TOut> : CollectionAdapterBase<TIn, TOut, ICollection<TIn>>
{
    public ReadOnlyCollectionAdapter(ICollection<TIn> collection, Func<TIn, TOut> toOuter)
        : base(() => collection, toOuter)
    {
    }

    public override void Add(TOut item) { throw new NotImplementedException(); }

    public override void Clear() { throw new NotImplementedException(); }

    public override bool IsReadOnly { get { return true; } }

    public override bool Remove(TOut item) { throw new NotImplementedException(); }
}

public abstract class CollectionAdapterBase<TIn, TOut, TCollection> : ICollection<TOut> 
    where TCollection : ICollection<TIn>
{
    readonly Func<TCollection> getCollection;
    readonly Func<TIn, TOut> toOuter;

    public CollectionAdapterBase(Func<TCollection> getCollection, Func<TIn, TOut> toOuter)
    {
        if (getCollection == null || toOuter == null)
            throw new ArgumentNullException();
        this.getCollection = getCollection;
        this.toOuter = toOuter;
    }

    protected TCollection Collection { get { return getCollection(); } }

    protected TOut ToOuter(TIn inner) { return toOuter(inner); }

    #region ICollection<TOut> Members

    public abstract void Add(TOut item);

    public abstract void Clear();

    public virtual bool Contains(TOut item)
    {
        var comparer = EqualityComparer<TOut>.Default;
        foreach (var member in Collection)
            if (comparer.Equals(item, ToOuter(member)))
                return true;
        return false;
    }

    public void CopyTo(TOut[] array, int arrayIndex)
    {
        foreach (var item in this)
            array[arrayIndex++] = item;
    }

    public int Count { get { return Collection.Count; } }

    public abstract bool IsReadOnly { get; }

    public abstract bool Remove(TOut item);

    #endregion

    #region IEnumerable<TOut> Members

    public IEnumerator<TOut> GetEnumerator()
    {
        foreach (var item in Collection)
            yield return ToOuter(item);
    }

    #endregion

    #region IEnumerable Members

    IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }

    #endregion
}

然后可以通过执行以下操作为给定构造一个adapted NameValueCollection Data：

var adapter = Data.ToDictionaryAdapter();

笔记：

  • 使用适配器可能比简单地创建一个复制的字典更高效，并且应该与任何完全支持字典序列化的序列化程序一起工作。

    NameValueCollection适配器在将 a与任何其他需要某种类型的代码一起使用时也可能很有用IDictionary——这是适配器模式的基本优势。

  • 话虽如此，JavaScriptSerializer不能与适配器一起使用，因为此序列化程序无法序列化IDictionary<TKey, TValue>不继承自Dictionary<TKey, TValue>. 有关详细信息，请参阅使用 JavaScriptSerializer 序列化字典。

  • 使用时DataContractJsonSerializer，可以通过使用数据契约代理机制NameValueCollection将 a 替换为序列化图中的适配器。

  • 使用 Json.NET 时，可以使用以下自定义NameValueCollection适配器替换为适配器：JsonConverter

    public class NameValueJsonConverter<TNameValueCollection> : JsonConverter
    where TNameValueCollection : NameValueCollection, new()
{
    public override bool CanConvert(Type objectType)
    {
        return typeof(TNameValueCollection).IsAssignableFrom(objectType);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.SkipComments().TokenType == JsonToken.Null)
            return null;

        // Reuse the existing NameValueCollection if present
        var collection = (TNameValueCollection)existingValue ?? new TNameValueCollection();
        var dictionaryWrapper = collection.ToDictionaryAdapter();

        serializer.Populate(reader, dictionaryWrapper);

        return collection;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var collection = (TNameValueCollection)value;
        var dictionaryWrapper = new NameValueCollectionDictionaryAdapter<TNameValueCollection>(collection);
        serializer.Serialize(writer, dictionaryWrapper);
    }
}

public static partial class JsonExtensions
{
    public static JsonReader SkipComments(this JsonReader reader)
    {
        while (reader.TokenType == JsonToken.Comment && reader.Read())
            ;
        return reader;
    }
}

    可以使用如下：

    string json = JsonConvert.SerializeObject(Data, Formatting.Indented, new NameValueJsonConverter<NameValueCollection>());

  • NameValueCollection支持以下所有

    • 给定键的null值；
    • 给定键的多个值（在这种情况下NameValueCollection.Item[String]返回逗号分隔的值列表）；
    • 包含嵌入逗号的单个值（使用 时无法与多个值的情况区分开来NameValueCollection.Item[String]）。


    因此，适配器必须实现IDictionary<string, string[]>而不是IDictionary<string, string>并且还要小​​心处理null值数组。

小提琴示例（包括一些基本的单元测试）：https ://dotnetfiddle.net/gVPSi7

于 2018-10-09T20:28:33.957 回答