fix ProblemDetail Deserialize, add a QueryString IEnumerable overload

src/FluentRest/ProblemDetails.cs

@@ -1,11 +1,12 @@
 using System.Text.Json.Serialization;
 
+#nullable enable
+
 namespace FluentRest;
 
 /// <summary>
 /// A machine-readable format for specifying errors in HTTP API responses based on https://tools.ietf.org/html/rfc7807.
 /// </summary>
-[JsonConverter(typeof(ProblemDetailsConverter))]
 public class ProblemDetails
 {
     /// <summary>
@@ -14,43 +15,67 @@ public class ProblemDetails
     public const string ContentType = "application/problem+json";
 
     /// <summary>
-    /// A URI reference that identifies the problem type.
+    /// A URI reference [RFC3986] that identifies the problem type. This specification encourages that, when
+    /// dereferenced, it provide human-readable documentation for the problem type
+    /// (e.g., using HTML [W3C.REC-html5-20141028]). When this member is not present, its value is assumed to be
+    /// "about:blank".
     /// </summary>
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyOrder(-5)]
     [JsonPropertyName("type")]
-    public string Type { get; set; }
+    public string? Type { get; set; }
 
     /// <summary>
-    /// A short, human-readable summary of the problem type.
+    /// A short, human-readable summary of the problem type. It SHOULD NOT change from occurrence to occurrence
+    /// of the problem, except for purposes of localization(e.g., using proactive content negotiation;
+    /// see[RFC7231], Section 3.4).
     /// </summary>
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyOrder(-4)]
     [JsonPropertyName("title")]
-    public string Title { get; set; }
+    public string? Title { get; set; }
 
     /// <summary>
-    /// The HTTP status code generated by the origin server for this occurrence of the problem.
+    /// The HTTP status code([RFC7231], Section 6) generated by the origin server for this occurrence of the problem.
     /// </summary>
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyOrder(-3)]
     [JsonPropertyName("status")]
     public int? Status { get; set; }
 
     /// <summary>
     /// A human-readable explanation specific to this occurrence of the problem.
     /// </summary>
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyOrder(-2)]
     [JsonPropertyName("detail")]
-    public string Detail { get; set; }
+    public string? Detail { get; set; }
 
     /// <summary>
-    /// A URI reference that identifies the specific occurrence of the problem.
+    /// A URI reference that identifies the specific occurrence of the problem. It may or may not yield further information if dereferenced.
     /// </summary>
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyOrder(-1)]
     [JsonPropertyName("instance")]
-    public string Instance { get; set; }
+    public string? Instance { get; set; }
+
+    /// <summary>
+    /// Gets the validation errors associated with this instance of problem details
+    /// </summary>
+    [JsonPropertyName("errors")]
+    public IDictionary<string, string[]> Errors { get; set; } = new Dictionary<string, string[]>(StringComparer.Ordinal);
 
     /// <summary>
-    /// Problem type definitions MAY extend the problem details object with additional members.
+    /// Gets the <see cref="IDictionary{TKey, TValue}"/> for extension members.
+    /// <para>
+    /// Problem type definitions MAY extend the problem details object with additional members. Extension members appear in the same namespace as
+    /// other members of a problem type.
+    /// </para>
     /// </summary>
+    /// <remarks>
+    /// The round-tripping behavior for <see cref="Extensions"/> is determined by the implementation of the Input \ Output formatters.
+    /// In particular, complex types or collection types may not round-trip to the original type when using the built-in JSON or XML formatters.
+    /// </remarks>
     [JsonExtensionData]
-    public IDictionary<string, object> Extensions { get; } = new Dictionary<string, object>(StringComparer.Ordinal);
+    public IDictionary<string, object?> Extensions { get; set; } = new Dictionary<string, object?>(StringComparer.Ordinal);
 }

src/FluentRest/QueryBuilder.cs

@@ -374,6 +374,34 @@ public TBuilder QueryString<TValue>(string name, TValue value)
         return QueryString(name, v);
     }
 
+    /// <summary>
+    /// Appends the specified <paramref name="name" /> and <paramref name="values" /> to the request Uri.
+    /// </summary>
+    /// <typeparam name="TValue">The type of the value.</typeparam>
+    /// <param name="name">The query parameter name.</param>
+    /// <param name="values">The query parameter values.</param>
+    /// <returns>
+    /// A fluent request builder.
+    /// </returns>
+    /// <exception cref="System.ArgumentNullException"><paramref name="name" /> is <see langword="null" />.</exception>
+    public TBuilder QueryString<TValue>(string name, IEnumerable<TValue> values)
+    {
+        if (name == null)
+            throw new ArgumentNullException(nameof(name));
+
+        if (values == null)
+            return this as TBuilder;
+
+        foreach (var value in values)
+        {
+            var v = value != null ? value.ToString() : string.Empty;
+            QueryString(name, v);
+        }
+
+        return this as TBuilder;
+    }
+
+
     /// <summary>
     /// Appends the specified <paramref name="name"/> and <paramref name="value"/> to the request Uri if the specified <paramref name="condition"/> is true.
     /// </summary>

src/FluentRest/UrlBuilder.cs

@@ -454,6 +454,31 @@ public UrlBuilder AppendQuery<TValue>(string name, TValue value)
         return AppendQuery(name, v);
     }
 
+    /// <summary>
+    /// Appends the query string name and values to the current url.
+    /// </summary>
+    /// <typeparam name="TValue">The type of the value.</typeparam>
+    /// <param name="name">The query string name.</param>
+    /// <param name="values">The query string values.</param>
+    /// <returns></returns>
+    /// <exception cref="ArgumentNullException">name is <c>null</c></exception>
+    public UrlBuilder AppendQuery<TValue>(string name, IEnumerable<TValue> values)
+    {
+        if (name == null)
+            throw new ArgumentNullException(nameof(name));
+
+        if (values == null)
+            return this;
+
+        foreach (var value in values)
+        {
+            var v = value != null ? value.ToString() : string.Empty;
+            AppendQuery(name, v);
+        }
+
+        return this;
+    }
+
     /// <summary>
     /// Conditionally appends the query string name and value to the current url if the specified <paramref name="condition" /> is <c>true</c>.
     /// </summary>

test/FluentRest.Tests/FluentRest.Tests.csproj

@@ -2,6 +2,7 @@
   <PropertyGroup>
     <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
+    <LangVersion>Latest</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\FluentRest\FluentRest.csproj" />

test/FluentRest.Tests/ProblemDetailsTests.cs

@@ -0,0 +1,80 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+using FluentAssertions;
+
+using Xunit;
+
+namespace FluentRest.Tests;
+
+public class ProblemDetailsTests
+{
+    [Fact]
+    public void DeserializeBadRequestValidation()
+    {
+        var options = CreateOptions();
+
+        var json = @"{
+    ""type"": ""https://tools.ietf.org/html/rfc9110#section-15.5.1"",
+    ""title"": ""One or more validation errors occurred."",
+    ""status"": 400,
+    ""errors"": {
+        ""caseManagerIds"": [
+            ""The value 'System.Collections.Generic.List`1[System.Int32]' is not valid.""
+        ]
+    },
+    ""traceId"": ""00-894a84e8e9621fb8fcabcb2911e6d51c-5a4777d830f30cff-00""
+}";
+        var problemDetails = JsonSerializer.Deserialize<ProblemDetails>(json, options);
+        problemDetails.Should().NotBeNull();
+        problemDetails.Title.Should().Be("One or more validation errors occurred.");
+        problemDetails.Status.Should().Be(400);
+    }
+
+
+
+    [Fact]
+    public void DeserializeServerError()
+    {
+        var options = CreateOptions();
+
+        var json = @"{
+    ""type"": ""https://tools.ietf.org/html/rfc9110#section-15.5.1"",
+    ""title"": ""One or more errors occurred."",
+    ""status"": 500,
+    ""traceId"": ""00-894a84e8e9621fb8fcabcb2911e6d51c-5a4777d830f30cff-00""
+}";
+        var problemDetails = JsonSerializer.Deserialize<ProblemDetails>(json, options);
+        problemDetails.Should().NotBeNull();
+        problemDetails.Title.Should().Be("One or more errors occurred.");
+        problemDetails.Status.Should().Be(500);
+    }
+
+    [Fact]
+    public void DeserializeServerErrorExtra()
+    {
+        var options = CreateOptions();
+
+        var json = @"{
+    ""type"": ""https://tools.ietf.org/html/rfc9110#section-15.5.1"",
+    ""title"": ""One or more errors occurred."",
+    ""status"": 500,
+    ""exception"": ""this is an exception"",
+    ""traceId"": ""00-894a84e8e9621fb8fcabcb2911e6d51c-5a4777d830f30cff-00""
+}";
+        var problemDetails = JsonSerializer.Deserialize<ProblemDetails>(json, options);
+        problemDetails.Should().NotBeNull();
+        problemDetails.Title.Should().Be("One or more errors occurred.");
+        problemDetails.Status.Should().Be(500);
+    }
+
+    private static JsonSerializerOptions CreateOptions()
+    {
+        var options = new JsonSerializerOptions(JsonSerializerDefaults.Web);
+        options.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
+        options.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault;
+        options.Converters.Add(new JsonStringEnumConverter(JsonNamingPolicy.CamelCase));
+        options.TypeInfoResolverChain.Add(ProblemDetailsJsonContext.Default);
+        return options;
+    }
+}

test/FluentRest.Tests/QueryBuilderTest.cs

@@ -38,6 +38,20 @@ public void QueryStringMultipleValue()
         Assert.Equal("http://test.com/?Test=Test1&Test=Test2", uri.ToString());
     }
 
+    [Fact]
+    public void QueryStringMultipleList()
+    {
+        var request = new HttpRequestMessage();
+        var builder = new QueryBuilder(request);
+
+        builder.BaseUri("http://test.com/");
+        builder.QueryString("Test", ["Test1", "Test2"]);
+
+        var uri = request.GetUrlBuilder();
+
+        Assert.Equal("http://test.com/?Test=Test1&Test=Test2", uri.ToString());
+    }
+
     [Fact]
     public void HeaderSingleValue()
     {