Add JsonConverter classes for Date and Time to support System.Text.Json deserialization

src/serialization/json/DateJsonConverter.cs

@@ -0,0 +1,44 @@
+// ------------------------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.  See License in the project root for license information.
+// ------------------------------------------------------------------------------
+
+using System;
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.Kiota.Abstractions;
+
+namespace Microsoft.Kiota.Serialization.Json;
+
+/// <summary>
+/// Converts a Date object or value to/from JSON.
+/// </summary>
+public class DateJsonConverter : JsonConverter<Date>
+{
+    /// <inheritdoc />
+    public override Date Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        if(reader.TokenType == JsonTokenType.Null)
+            return default;
+
+        if(reader.TokenType == JsonTokenType.String)
+        {
+            var stringValue = reader.GetString();
+            if(string.IsNullOrEmpty(stringValue))
+                return default;
+
+            if(DateTime.TryParse(stringValue, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out var dateTime))
+                return new Date(dateTime);
+
+            throw new JsonException($"Unable to parse '{stringValue}' as a Date.");
+        }
+
+        throw new JsonException($"Unexpected token type '{reader.TokenType}' when reading Date.");
+    }
+
+    /// <inheritdoc />
+    public override void Write(Utf8JsonWriter writer, Date value, JsonSerializerOptions options)
+    {
+        writer.WriteStringValue(value.ToString());
+    }
+}

src/serialization/json/KiotaJsonSerializationContext.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Text.Json;
 using System.Text.Json.Serialization;
 using Microsoft.Kiota.Abstractions;
 
@@ -34,4 +35,24 @@ namespace Microsoft.Kiota.Serialization.Json;
 [JsonSerializable(typeof(Date?))]
 [JsonSerializable(typeof(Time))]
 [JsonSerializable(typeof(Time?))]
-public partial class KiotaJsonSerializationContext : JsonSerializerContext;
+public partial class KiotaJsonSerializationContext : JsonSerializerContext
+{
+    private static JsonSerializerOptions? _defaultOptionsWithConverters;
+
+    /// <summary>
+    /// Gets the default <see cref="JsonSerializerOptions"/> with Date and Time converters registered.
+    /// </summary>
+    public static JsonSerializerOptions DefaultOptionsWithConverters
+    {
+        get
+        {
+            if(_defaultOptionsWithConverters == null)
+            {
+                _defaultOptionsWithConverters = new JsonSerializerOptions(Default.Options);
+                _defaultOptionsWithConverters.Converters.Add(new DateJsonConverter());
+                _defaultOptionsWithConverters.Converters.Add(new TimeJsonConverter());
+            }
+            return _defaultOptionsWithConverters;
+        }
+    }
+}

src/serialization/json/README.md

@@ -12,6 +12,50 @@ Read more about Kiota [here](https://github.com/microsoft/kiota/blob/main/README
 dotnet add package Microsoft.Kiota.Serialization.Json
 ```
 
+## Using Date and Time Converters with System.Text.Json
+
+The library provides `DateJsonConverter` and `TimeJsonConverter` to enable serialization and deserialization of Kiota's `Date` and `Time` types when using `System.Text.Json.JsonSerializer` directly (outside of Kiota's serialization infrastructure).
+
+### Option 1: Using DefaultOptionsWithConverters
+
+The simplest approach is to use the pre-configured options with converters:
+
+```csharp
+using Microsoft.Kiota.Abstractions;
+using Microsoft.Kiota.Serialization.Json;
+using System.Text.Json;
+
+var date = new Date(2025, 10, 24);
+var json = JsonSerializer.Serialize(date, KiotaJsonSerializationContext.DefaultOptionsWithConverters);
+// Output: "2025-10-24"
+
+var deserialized = JsonSerializer.Deserialize<Date>(json, KiotaJsonSerializationContext.DefaultOptionsWithConverters);
+// deserialized.Year == 2025, deserialized.Month == 10, deserialized.Day == 24
+```
+
+### Option 2: Manually Registering Converters
+
+You can also manually register the converters with your own `JsonSerializerOptions`:
+
+```csharp
+using Microsoft.Kiota.Abstractions;
+using Microsoft.Kiota.Serialization.Json;
+using System.Text.Json;
+
+var options = new JsonSerializerOptions();
+options.Converters.Add(new DateJsonConverter());
+options.Converters.Add(new TimeJsonConverter());
+
+var time = new Time(10, 18, 54);
+var json = JsonSerializer.Serialize(time, options);
+// Output: "10:18:54"
+
+var deserialized = JsonSerializer.Deserialize<Time>(json, options);
+// deserialized.Hour == 10, deserialized.Minute == 18, deserialized.Second == 54
+```
+
+This is particularly useful when integrating with third-party libraries that serialize/deserialize Kiota-generated models but cannot use Kiota's serialization infrastructure.
+
 ## Debugging
 
 If you are using Visual Studio Code as your IDE, the **launch.json** file already contains the configuration to build and test the library. Otherwise, you can open the **Microsoft.Kiota.Serialization.Json.sln** with Visual Studio.

src/serialization/json/TimeJsonConverter.cs

@@ -0,0 +1,44 @@
+// ------------------------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.  See License in the project root for license information.
+// ------------------------------------------------------------------------------
+
+using System;
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.Kiota.Abstractions;
+
+namespace Microsoft.Kiota.Serialization.Json;
+
+/// <summary>
+/// Converts a Time object or value to/from JSON.
+/// </summary>
+public class TimeJsonConverter : JsonConverter<Time>
+{
+    /// <inheritdoc />
+    public override Time Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        if(reader.TokenType == JsonTokenType.Null)
+            return default;
+
+        if(reader.TokenType == JsonTokenType.String)
+        {
+            var stringValue = reader.GetString();
+            if(string.IsNullOrEmpty(stringValue))
+                return default;
+
+            if(DateTime.TryParse(stringValue, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out var dateTime))
+                return new Time(dateTime);
+
+            throw new JsonException($"Unable to parse '{stringValue}' as a Time.");
+        }
+
+        throw new JsonException($"Unexpected token type '{reader.TokenType}' when reading Time.");
+    }
+
+    /// <inheritdoc />
+    public override void Write(Utf8JsonWriter writer, Time value, JsonSerializerOptions options)
+    {
+        writer.WriteStringValue(value.ToString());
+    }
+}

tests/serialization/json/DateJsonConverterTests.cs

@@ -0,0 +1,99 @@
+// ------------------------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.  See License in the project root for license information.
+// ------------------------------------------------------------------------------
+
+using System;
+using System.Text.Json;
+using Microsoft.Kiota.Abstractions;
+using Xunit;
+
+namespace Microsoft.Kiota.Serialization.Json.Tests;
+
+public class DateJsonConverterTests
+{
+    private readonly JsonSerializerOptions _options;
+
+    public DateJsonConverterTests()
+    {
+        _options = new JsonSerializerOptions();
+        _options.Converters.Add(new DateJsonConverter());
+    }
+
+    [Fact]
+    public void SerializesDateAsString()
+    {
+        var date = new Date(2025, 10, 24);
+        var json = JsonSerializer.Serialize(date, _options);
+
+        Assert.Equal("\"2025-10-24\"", json);
+    }
+
+    [Fact]
+    public void DeserializesDateFromString()
+    {
+        var json = "\"2025-10-24\"";
+        var date = JsonSerializer.Deserialize<Date>(json, _options);
+
+        Assert.Equal(2025, date.Year);
+        Assert.Equal(10, date.Month);
+        Assert.Equal(24, date.Day);
+    }
+
+    [Fact]
+    public void RoundTripSerialization()
+    {
+        var original = new Date(2025, 10, 24);
+        var json = JsonSerializer.Serialize(original, _options);
+        var deserialized = JsonSerializer.Deserialize<Date>(json, _options);
+
+        Assert.Equal(original.Year, deserialized.Year);
+        Assert.Equal(original.Month, deserialized.Month);
+        Assert.Equal(original.Day, deserialized.Day);
+    }
+
+    [Fact]
+    public void DeserializesNullToDefault()
+    {
+        var json = "null";
+        var date = JsonSerializer.Deserialize<Date>(json, _options);
+
+        Assert.Equal(default(Date), date);
+    }
+
+    [Fact]
+    public void DeserializesEmptyStringToDefault()
+    {
+        var json = "\"\"";
+        var date = JsonSerializer.Deserialize<Date>(json, _options);
+
+        Assert.Equal(default(Date), date);
+    }
+
+    [Fact]
+    public void ThrowsOnInvalidFormat()
+    {
+        var json = "\"not-a-date\"";
+
+        Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<Date>(json, _options));
+    }
+
+    [Fact]
+    public void ThrowsOnUnexpectedTokenType()
+    {
+        var json = "123";
+
+        Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<Date>(json, _options));
+    }
+
+    [Fact]
+    public void WorksWithDefaultOptionsWithConverters()
+    {
+        var date = new Date(2025, 10, 24);
+        var json = JsonSerializer.Serialize(date, KiotaJsonSerializationContext.DefaultOptionsWithConverters);
+        var deserialized = JsonSerializer.Deserialize<Date>(json, KiotaJsonSerializationContext.DefaultOptionsWithConverters);
+
+        Assert.Equal(date.Year, deserialized.Year);
+        Assert.Equal(date.Month, deserialized.Month);
+        Assert.Equal(date.Day, deserialized.Day);
+    }
+}

tests/serialization/json/TimeJsonConverterTests.cs

@@ -0,0 +1,99 @@
+// ------------------------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.  See License in the project root for license information.
+// ------------------------------------------------------------------------------
+
+using System;
+using System.Text.Json;
+using Microsoft.Kiota.Abstractions;
+using Xunit;
+
+namespace Microsoft.Kiota.Serialization.Json.Tests;
+
+public class TimeJsonConverterTests
+{
+    private readonly JsonSerializerOptions _options;
+
+    public TimeJsonConverterTests()
+    {
+        _options = new JsonSerializerOptions();
+        _options.Converters.Add(new TimeJsonConverter());
+    }
+
+    [Fact]
+    public void SerializesTimeAsString()
+    {
+        var time = new Time(10, 18, 54);
+        var json = JsonSerializer.Serialize(time, _options);
+
+        Assert.Equal("\"10:18:54\"", json);
+    }
+
+    [Fact]
+    public void DeserializesTimeFromString()
+    {
+        var json = "\"10:18:54\"";
+        var time = JsonSerializer.Deserialize<Time>(json, _options);
+
+        Assert.Equal(10, time.Hour);
+        Assert.Equal(18, time.Minute);
+        Assert.Equal(54, time.Second);
+    }
+
+    [Fact]
+    public void RoundTripSerialization()
+    {
+        var original = new Time(10, 18, 54);
+        var json = JsonSerializer.Serialize(original, _options);
+        var deserialized = JsonSerializer.Deserialize<Time>(json, _options);
+
+        Assert.Equal(original.Hour, deserialized.Hour);
+        Assert.Equal(original.Minute, deserialized.Minute);
+        Assert.Equal(original.Second, deserialized.Second);
+    }
+
+    [Fact]
+    public void DeserializesNullToDefault()
+    {
+        var json = "null";
+        var time = JsonSerializer.Deserialize<Time>(json, _options);
+
+        Assert.Equal(default(Time), time);
+    }
+
+    [Fact]
+    public void DeserializesEmptyStringToDefault()
+    {
+        var json = "\"\"";
+        var time = JsonSerializer.Deserialize<Time>(json, _options);
+
+        Assert.Equal(default(Time), time);
+    }
+
+    [Fact]
+    public void ThrowsOnInvalidFormat()
+    {
+        var json = "\"not-a-time\"";
+
+        Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<Time>(json, _options));
+    }
+
+    [Fact]
+    public void ThrowsOnUnexpectedTokenType()
+    {
+        var json = "123";
+
+        Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<Time>(json, _options));
+    }
+
+    [Fact]
+    public void WorksWithDefaultOptionsWithConverters()
+    {
+        var time = new Time(10, 18, 54);
+        var json = JsonSerializer.Serialize(time, KiotaJsonSerializationContext.DefaultOptionsWithConverters);
+        var deserialized = JsonSerializer.Deserialize<Time>(json, KiotaJsonSerializationContext.DefaultOptionsWithConverters);
+
+        Assert.Equal(time.Hour, deserialized.Hour);
+        Assert.Equal(time.Minute, deserialized.Minute);
+        Assert.Equal(time.Second, deserialized.Second);
+    }
+}