在AspNet Core中解析空查询参数

Question

如何在AspNet Core中处理空查询参数？

假设我们有一个查询 ?key1=foo1&key1=foo2&key2=&key3=null

当解析它时，我希望在解析此URL时会有某种字典>，例如：

• key1：[“ foo1”，“ foo2”]这应该是同一键下的多个值
• key2：[“”]这应该是一个空字符串
• key3：[“ null”]这应该是一个字符串，据我所知，URL中的null只是一个文字

我的问题是：我应该如何处理空查询参数？

注意：我无法简单地定义查询参数，并假设不存在的查询参数为null。但是我认为，如果需要，在显式查询参数中应将null视为有效值。

根据此线程：How to send NULL in HTTP query string? 标准是传递编码后的空值：请参见https://www.w3schools.com/tags/ref_urlencode.asp

因此，如果我想传递一个空值，我应该执行以下操作：?key1=foo1&key1=foo2&key2=&key3=%00

问题是我不知道如何解码，因此％00被解析为空值。

我尝试了以下方法：

public Dictionary<string, List<string>> CreateFromQuery(string query)
{
    if (query == null)
    {
        return new Dictionary<string, List<string>>();
    }

    var queryDictionary = Microsoft.AspNetCore.WebUtilities.QueryHelpers.ParseQuery(query);

    var result = queryDictionary.ToDictionary(kv => kv.Key, kv => kv.Value.ToList());
    return result;
}

但是%00会转换为"\0"字符串，而不是null。

先做var decodedQuery= HttpUtility.UrlDecode(query);似乎也没有任何作用。

UPDATE1 ：在Kacper和Chris Pratt发表评论（谢谢大家）之后，我暂时接受了Kacper的第二条建议，因为我认为提出请求者想要区分空查询的场景很有趣。参数，空查询参数和不存在的查询参数。

这是我当前的实现方式：

public class QueryParserFactory
    : IQueryParseable
{
    public Dictionary<string, List<string>> CreateFromQuery(string query)
    {
        if (query == null)
        {
            return new Dictionary<string, List<string>>();
        }

        var queryDecoded = HttpUtility.UrlDecode(query);

        var queryDictionary = QueryHelpers.ParseQuery(queryDecoded);

        var result = queryDictionary
            .ToDictionary(
                kv => kv.Key,
                kv => kv.Value.Select(s => s == "\0" ? null : s).ToList());
        return result;
    }
}

如果有人感兴趣，下面我可以想到所有的单元测试：

public static class CreateFromQueryTests
{
    public class Given_An_Empty_Query_String_When_Creating_From_A_Query
        : Given_When_Then_Test
    {
        private QueryParserFactory _sut;
        private Dictionary<string, List<string>> _result;

        protected override void Given()
        {
            _sut = new QueryParserFactory();
        }

        protected override void When()
        {
            _result = _sut.CreateFromQuery("");
        }

        [Fact]
        public void Then_It_Should_Return_A_Valid_Result()
        {
            _result.Should().NotBeNull();
        }

        [Fact]
        public void Then_It_Should_Not_Have_Any_Key()
        {
            _result.Keys.Count.Should().Be(0);
        }

        [Fact]
        public void Then_It_Should_Not_Have_Any_Items_In_Dictionary()
        {
            _result.Count.Should().Be(0);
        }
    }

    public class Given_A_Query_String_With_Empty_Values_When_Creating_From_A_Query
        : Given_When_Then_Test
    {
        private QueryParserFactory _sut;
        private Dictionary<string, List<string>> _result;
        private List<string> _expectedValueForKey1;
        private List<string> _expectedValueForKey2;

        protected override void Given()
        {
            _expectedValueForKey1 = new List<string>
            {
                string.Empty
            };

            _expectedValueForKey2 = new List<string>
            {
                string.Empty
            };

            _sut = new QueryParserFactory();
        }

        protected override void When()
        {
            _result = _sut.CreateFromQuery("?key1=&key2=");
        }

        [Fact]
        public void Then_It_Should_Return_A_Valid_Result()
        {
            _result.Should().NotBeNull();
        }

        [Fact]
        public void Then_It_Should_Have_Key_For_All_Fulfilled_Parameters()
        {
            _result.Keys.Count.Should().Be(2);
        }

        [Fact]
        public void Then_It_Should_Have_Empty_Value_For_The_First_Key_Parameter()
        {
            _result["key1"].Should().BeEquivalentTo(_expectedValueForKey1);
        }

        [Fact]
        public void Then_It_Should_Have_Empty_Value_For_The_Second_Key_Parameter()
        {
            _result["key2"].Should().BeEquivalentTo(_expectedValueForKey2);
        }
    }

    public class Given_A_Query_String_With_Single_Values_When_Creating_From_A_Query
        : Given_When_Then_Test
    {
        private QueryParserFactory _sut;
        private Dictionary<string, List<string>> _result;
        private List<string> _expectedValueForKey1;
        private List<string> _expectedValueForKey2;

        protected override void Given()
        {
            _expectedValueForKey1 = new List<string>()
            {
                "value1"
            };

            _expectedValueForKey2 = new List<string>()
            {
                "value2"
            };

            _sut = new QueryParserFactory();
        }

        protected override void When()
        {
            _result = _sut.CreateFromQuery("?key1=value1&key2=value2");
        }

        [Fact]
        public void Then_It_Should_Return_A_Valid_Result()
        {
            _result.Should().NotBeNull();
        }

        [Fact]
        public void Then_It_Should_Have_Key_For_All_Fulfilled_Parameters()
        {
            _result.Keys.Count.Should().Be(2);
        }

        [Fact]
        public void Then_It_Should_Have_The_Correct_Multiple_Values_For_Keys_With_Multiple_Parameters()
        {
            _result["key1"].Should().BeEquivalentTo(_expectedValueForKey1);
        }

        [Fact]
        public void Then_It_Should_Have_The_Correct_Single_Value_For_Keys_With_One_Parameter()
        {
            _result["key2"].Should().BeEquivalentTo(_expectedValueForKey2);
        }

        [Fact]
        public void Then_It_Should_Not_Have_Entries_For_Inexistent_Parameters()
        {
            _result.TryGetValue("key3", out List<string> _).Should().BeFalse();
        }
    }

    public class Given_A_Query_String_With_Multiple_Values_For_The_Same_Key_When_Creating_From_A_Query
        : Given_When_Then_Test
    {
        private QueryParserFactory _sut;
        private Dictionary<string, List<string>> _result;
        private List<string> _expectedValueForKey1;

        protected override void Given()
        {
            _expectedValueForKey1 = new List<string>()
            {
                "value1",
                "value2",
                "value3"
            };

            _sut = new QueryParserFactory();
        }

        protected override void When()
        {
            _result = _sut.CreateFromQuery("?key1=value1&key1=value2&key1=value3");
        }

        [Fact]
        public void Then_It_Should_Return_A_Valid_Result()
        {
            _result.Should().NotBeNull();
        }

        [Fact]
        public void Then_It_Should_Have_Only_One_Key()
        {
            _result.Keys.Count.Should().Be(1);
        }

        [Fact]
        public void Then_It_Should_Have_The_Correct_Multiple_Values_For_Keys_With_Multiple_Parameters()
        {
            _result["key1"].Should().BeEquivalentTo(_expectedValueForKey1);
        }

        [Fact]
        public void Then_It_Should_Not_Have_Entries_For_Inexistent_Parameters()
        {
            _result.TryGetValue("key2", out List<string> _).Should().BeFalse();
        }
    }

    public class Given_A_Query_String_With_Non_Url_Encoded_Null_Values_When_Creating_From_A_Query
        : Given_When_Then_Test
    {
        private QueryParserFactory _sut;
        private Dictionary<string, List<string>> _result;
        private List<string> _expectedValueForKey1;
        private List<string> _expectedValueForKey2;

        protected override void Given()
        {
            _expectedValueForKey1 = new List<string>()
            {
                "null"
            };

            _expectedValueForKey2 = new List<string>()
            {
                "null"
            };

            _sut = new QueryParserFactory();
        }

        protected override void When()
        {
            _result = _sut.CreateFromQuery("?key1=null&key2=null");
        }

        [Fact]
        public void Then_It_Should_Return_A_Valid_Result()
        {
            _result.Should().NotBeNull();
        }

        [Fact]
        public void Then_It_Should_Have_Key_For_All_Fulfilled_Parameters()
        {
            _result.Keys.Count.Should().Be(2);
        }

        [Fact]
        public void Then_It_Should_Have_A_Null_Literal_For_The_First_Parameter()
        {
            _result["key1"].Should().BeEquivalentTo(_expectedValueForKey1);
        }

        [Fact]
        public void Then_It_Should_Have_A_Null_Literal_For_The_Second_Parameter()
        {
            _result["key2"].Should().BeEquivalentTo(_expectedValueForKey2);
        }

        [Fact]
        public void Then_It_Should_Not_Have_Entries_For_Inexistent_Parameters()
        {
            _result.TryGetValue("key3", out List<string> _).Should().BeFalse();
        }
    }

    public class Given_A_Query_String_With_Url_Encoded_Null_Values_When_Creating_From_A_Query
        : Given_When_Then_Test
    {
        private QueryParserFactory _sut;
        private Dictionary<string, List<string>> _result;
        private List<string> _expectedValueForKey1;
        private List<string> _expectedValueForKey2;

        protected override void Given()
        {
            _expectedValueForKey1 = new List<string>()
            {
                null
            };

            _expectedValueForKey2 = new List<string>()
            {
                null
            };

            _sut = new QueryParserFactory();
        }

        protected override void When()
        {
            _result = _sut.CreateFromQuery("?key1=%00&key2=%00");
        }

        [Fact]
        public void Then_It_Should_Return_A_Valid_Result()
        {
            _result.Should().NotBeNull();
        }

        [Fact]
        public void Then_It_Should_Have_Key_For_All_Fulfilled_Parameters()
        {
            _result.Keys.Count.Should().Be(2);
        }

        [Fact]
        public void Then_It_Should_Have_A_Null_Literal_For_The_First_Parameter()
        {
            _result["key1"].Should().BeEquivalentTo(_expectedValueForKey1);
        }

        [Fact]
        public void Then_It_Should_Have_A_Null_Literal_For_The_Second_Parameter()
        {
            _result["key2"].Should().BeEquivalentTo(_expectedValueForKey2);
        }

        [Fact]
        public void Then_It_Should_Not_Have_Entries_For_Inexistent_Parameters()
        {
            _result.TryGetValue("key3", out List<string> _).Should().BeFalse();
        }
    }
}

Answer 1

我找不到任何内置的东西来做。所以我有两种选择，取决于适合您的情况。

1。

public Dictionary<string, List<string>> CreateFromQuery(string query)
{
    if (query == null)
    {
        return new Dictionary<string, List<string>>();
    }

    var queryDictionary = Microsoft.AspNetCore.WebUtilities.QueryHelpers.ParseQuery(query);

    var result = queryDictionary
       .ToDictionary(
           kv => kv.Key, 
           kv => kv.Value.Select(s => s.Trim("\0")).ToList()); //There you will have String.Empty
    return result;
}

2。

public Dictionary<string, List<string>> CreateFromQuery(string query)
{
    if (query == null)
    {
        return new Dictionary<string, List<string>>();
    }

    var queryDictionary = Microsoft.AspNetCore.WebUtilities.QueryHelpers.ParseQuery(query);

    var result = queryDictionary
       .ToDictionary(
           kv => kv.Key, 
           kv => kv.Value.Select(s => s == "\0" ? null : s).ToList()); //There you will have nulls
    return result;
}

Answer 2

传递null的方法是根本不传递任何值，或者完全不包含键，即：

?key1=foo1&key1=foo2&key2=&key3=

或者简单地：

?key1=foo1&key1=foo2&key2=

对于您的key2参数，您应该意识到无法传递空字符串。 ASP.NET Core会将其解释为空值。如果您具有实际上不应该为null的字符串属性（即，在这种情况下，您希望它始终为空字符串），则可以通过自定义getter进行处理。

private string key2;
public string Key2
{
    get => key2 ?? string.Empty;
    set => key2 = value;
}

然后，在将其设置为空值的情况下，它将替代为空字符串。