KeyValuePairConverter.cs

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using System.Collections.Generic;
using System.Reflection;
using System.Text.Json.Serialization.Metadata;
 
namespace System.Text.Json.Serialization.Converters;
 
internal sealed class KeyValuePairConverter<TKey, TValue> : SmallObjectWithParameterizedConstructorConverter<KeyValuePair<TKey, TValue>, TKey, TValue, object, object>
{
    private string _keyName;
 
    private string _valueName;
 
    private static readonly ConstructorInfo s_constructorInfo = typeof(KeyValuePair<TKey, TValue>).GetConstructor(new Type[2]
    {
        typeof(TKey),
        typeof(TValue)
    });
 
    internal override void Initialize(JsonSerializerOptions options, JsonTypeInfo jsonTypeInfo = null)
    {
        JsonNamingPolicy propertyNamingPolicy = options.PropertyNamingPolicy;
        if (propertyNamingPolicy == null)
        {
            _keyName = "Key";
            _valueName = "Value";
        }
        else
        {
            _keyName = propertyNamingPolicy.ConvertName("Key");
            _valueName = propertyNamingPolicy.ConvertName("Value");
        }
        base.ConstructorInfo = s_constructorInfo;
    }
 
    protected override bool TryLookupConstructorParameter(ref ReadStack state, ref Utf8JsonReader reader, JsonSerializerOptions options, out JsonParameterInfo jsonParameterInfo)
    {
        JsonTypeInfo jsonTypeInfo = state.Current.JsonTypeInfo;
        ArgumentState ctorArgumentState = state.Current.CtorArgumentState;
        bool propertyNameCaseInsensitive = options.PropertyNameCaseInsensitive;
        string @string = reader.GetString();
        state.Current.JsonPropertyNameAsString = @string;
        if (!ctorArgumentState.FoundKey && FoundKeyProperty(@string, propertyNameCaseInsensitive))
        {
            jsonParameterInfo = jsonTypeInfo.ParameterCache[_keyName];
            ctorArgumentState.FoundKey = true;
        }
        else
        {
            if (ctorArgumentState.FoundValue || !FoundValueProperty(@string, propertyNameCaseInsensitive))
            {
                ThrowHelper.ThrowJsonException();
                jsonParameterInfo = null;
                return false;
            }
            jsonParameterInfo = jsonTypeInfo.ParameterCache[_valueName];
            ctorArgumentState.FoundValue = true;
        }
        ctorArgumentState.ParameterIndex++;
        ctorArgumentState.JsonParameterInfo = jsonParameterInfo;
        state.Current.NumberHandling = jsonParameterInfo.NumberHandling;
        return true;
    }
 
    protected override void EndRead(ref ReadStack state)
    {
        if (state.Current.CtorArgumentState.ParameterIndex != 2)
        {
            ThrowHelper.ThrowJsonException();
        }
    }
 
    private bool FoundKeyProperty(string propertyName, bool caseInsensitiveMatch)
    {
        if (!(propertyName == _keyName) && (!caseInsensitiveMatch || !string.Equals(propertyName, _keyName, StringComparison.OrdinalIgnoreCase)))
        {
            return propertyName == "Key";
        }
        return true;
    }
 
    private bool FoundValueProperty(string propertyName, bool caseInsensitiveMatch)
    {
        if (!(propertyName == _valueName) && (!caseInsensitiveMatch || !string.Equals(propertyName, _valueName, StringComparison.OrdinalIgnoreCase)))
        {
            return propertyName == "Value";
        }
        return true;
    }
}