interface IMyInterface { [System.ComponentModel.DefaultValue(69)] int Property1 { get; set; } bool Property2 { get; set; } [System.ComponentModel.DefaultValue(true)] bool Property3 { get; set; } [System.ComponentModel.DefaultValue("Hello Roslyn!")] string Property4 { get; set; } CultureInfo Property5 { get; set; } [System.ComponentModel.DefaultValue(null)] TimeSpan Property6 { get; set; } } [StronglyTypedDictionary(targetType: typeof(IMyInterface), supportsDefaultValues: true)] internal partial class MyStronglyTypedDictionary : IMyInterface { private bool someCondition; protected override T GetOrDefault<T>(T defaultValue, [CallerMemberName] string name = null!) { switch (name) { case nameof(IMyInterface.Property3) when someCondition: defaultValue = (T)(object)false; break; default: break; } return base.GetOrDefault(defaultValue, name); } public CultureInfo Property5 { get => CultureInfo.GetCultureInfo(Get()); set => Set(value.Name); } }

internal partial class MyStronglyTypedDictionary : GeneratedBase<global::Demo.IMyInterface>, global::Demo.IMyInterface { public MyStronglyTypedDictionary(IStronglyTypedKeyValuePairAccessor stronglyTypedKeyValuePairAccessor) : base(stronglyTypedKeyValuePairAccessor) { } public MyStronglyTypedDictionary(global::System.Collections.Generic.IDictionary<string, object> dictionary) : base(dictionary) { } public int Property1 { get => GetOrDefault<int>(69); set => Set(value); } public bool Property2 { get => Get<bool>(); set => Set(value); } public bool Property3 { get => GetOrDefault<bool>(true); set => Set(value); } public string Property4 { get => GetOrDefault("Hello Roslyn!"); set => Set(value); } public string Property6 { get => GetOrDefault<System.TimeSpan>(default(System.TimeSpan)); set => Set(value); } } public abstract class GeneratedBase { private sealed class StronglyTypedKvpWrapper : IStronglyTypedKeyValuePairAccessor { private readonly global::System.Collections.Generic.IDictionary<string, object> dictionary; public StronglyTypedKvpWrapper(global::System.Collections.Generic.IDictionary<string, object> dictionary) { this.dictionary = dictionary; } public T Get<T>(string name) where T : unmanaged { return (T)dictionary[name]; } public string Get(string name) { return (string)dictionary[name]; } public bool TryGet<T>(string name, out T value) where T : unmanaged { var result = dictionary.TryGetValue(name, out object? v); value = v is not null ? (T)v : default; return result; } public bool TryGet(string name, [global::System.Diagnostics.CodeAnalysis.NotNullWhen(true)] out string? value) { var result = dictionary.TryGetValue(name, out object? v); value = (string?)v; return result; } public void Set<T>(string name, T value) where T : unmanaged { dictionary[name] = value; } public void Set(string name, string value) { dictionary[name] = value; } } private readonly IStronglyTypedKeyValuePairAccessor stronglyTypedKeyValuePairAccessor; private protected GeneratedBase(IStronglyTypedKeyValuePairAccessor stronglyTypedKeyValuePairAccessor) { this.stronglyTypedKeyValuePairAccessor = stronglyTypedKeyValuePairAccessor; } private protected GeneratedBase(global::System.Collections.Generic.IDictionary<string, object> dictionary) : this(new StronglyTypedKvpWrapper(dictionary)) { } protected T Get<T>([global::System.Runtime.CompilerServices.CallerMemberName] string name = null!) where T : unmanaged { return stronglyTypedKeyValuePairAccessor.Get<T>(name); } protected string Get([global::System.Runtime.CompilerServices.CallerMemberName] string name = null!) { return stronglyTypedKeyValuePairAccessor.Get(name); } [global::System.Runtime.CompilerServices.MethodImpl(global::System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)] protected virtual T GetOrDefault<T>(T defaultValue, [global::System.Runtime.CompilerServices.CallerMemberName] string name = null!) where T : unmanaged { return stronglyTypedKeyValuePairAccessor.TryGet(name, out T result) ? result : defaultValue; } [global::System.Runtime.CompilerServices.MethodImpl(global::System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)] protected virtual string GetOrDefault(string defaultValue, [global::System.Runtime.CompilerServices.CallerMemberName] string name = null!) { return stronglyTypedKeyValuePairAccessor.TryGet(name, out string? result) ? result : defaultValue; } protected void Set<T>(T value, [global::System.Runtime.CompilerServices.CallerMemberName] string name = null!) where T : unmanaged { stronglyTypedKeyValuePairAccessor.Set(name, value); } protected void Set(string value, [global::System.Runtime.CompilerServices.CallerMemberName] string name = null!) { stronglyTypedKeyValuePairAccessor.Set(name, value); } } public abstract class GeneratedBase<TInterface> : GeneratedBase { private protected GeneratedBase(IStronglyTypedKeyValuePairAccessor stronglyTypedKeyValuePairAccessor) : base(stronglyTypedKeyValuePairAccessor) { } private protected GeneratedBase(global::System.Collections.Generic.IDictionary<string, object> dictionary) : base(dictionary) { } public TProperty Get<TProperty>(global::System.Linq.Expressions.Expression<Func<TInterface, TProperty>> expression) where TProperty : unmanaged { return base.Get<TProperty>(GetMemberName(expression)); } public string Get(global::System.Linq.Expressions.Expression<Func<TInterface, string>> expression) { return base.Get(GetMemberName(expression)); } public void Set<TProperty>(global::System.Linq.Expressions.Expression<Func<TInterface, TProperty>> expression, TProperty value) where TProperty : unmanaged { base.Set<TProperty>(value, GetMemberName(expression)); } public void Set(global::System.Linq.Expressions.Expression<Func<TInterface, string>> expression, string value) { base.Set(value, GetMemberName(expression)); } private static string GetMemberName<TProperty>(global::System.Linq.Expressions.Expression<Func<TInterface, TProperty>> expression) { return expression.Body switch { global::System.Linq.Expressions.MemberExpression m => m.Member.Name, global::System.Linq.Expressions.UnaryExpression u when u.Operand is global::System.Linq.Expressions.MemberExpression m => m.Member.Name, _ => throw new global::System.NotImplementedException($"Invalid expression: {expression.GetType()}. Exprected accessor."), }; } }