dotnet-10

# .NET 10 + C# 14 WPF Development Reference .NET 10 is an LTS release (released November 2025, supported for 3 years). The paired language version is C# 14. The required tooling is .NET 10 SDK and Visual Studio 2026. ## Project Setup Target framework: `net10.0-windows` ```xml <Project Sdk="Microsoft.NET.Sdk"> <PropertyGroup> <OutputType>WinExe</OutputType> <TargetFramework>net10.0-windows</TargetFramework> <Nullable>enable</Nullable> <ImplicitUsings>enable</ImplicitUsings> <UseWPF>true</UseWPF> </PropertyGroup> </Project> ``` ## C# 14 New Language Features ### `field` keyword (backed properties) Access the compiler-generated backing field inside a property accessor without declaring a separate field: ```csharp public string Name { get; set => field = value ?? throw new ArgumentNullException(nameof(value)); } ``` ### Extension members New `extension` block syntax supports extension properties (instance and static) in addition to extension methods: ```csharp public static class MyExtensions { extension(IEnumerable<int> source) { public bool IsEmpty => !source.Any(); } } ``` Use `sequence.IsEmpty` as if it were an instance property. ### Null-conditional assignment `?.` can now appear on the left-hand side of an assignment: ```csharp // Before C# 14: if (customer is not null) customer.Order = GetCurrentOrder(); // C# 14: customer?.Order = GetCurrentOrder(); ``` Also works with compound assignment (`+=`, `-=`, etc.). Increment/decrement (`++`/`--`) are not supported. ### `nameof` with unbound generic types ```csharp nameof(List<>) // returns "List" ``` ### Lambda parameter modifiers without explicit types ```csharp TryParse<int> parse = (text, out result) => int.TryParse(text, out result); ``` ### Implicit `Span<T>` / `ReadOnlySpan<T>` conversions C# 14 adds first-class implicit conversions between `Span<T>`, `ReadOnlySpan<T>`, and `T[]`. ### `partial` constructors and events Instance constructors and events can now be declared as `partial` members (one defining declaration, one implementing declaration). ### User-defined compound assignment and increment/decrement operators Types can now define `+=`, `-=`, `++`, `--`, etc. ## WPF Changes in .NET 10 ### Grid short-form syntax (new) Column/row definitions can be written inline as a string: ```xaml <!-- Before --> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="1*" /> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="300" /> </Grid.ColumnDefinitions> </Grid> <!-- .NET 10 --> <Grid ColumnDefinitions="1*, Auto, 300" RowDefinitions="Auto, *, 25" /> ``` ### MessageBox new buttons and results (new) `MessageBoxButton` now includes: `AbortRetryIgnore`, `RetryCancel`, `CancelTryContinue`. `MessageBoxResult` now includes: `Abort`, `Retry`, `Ignore`, `TryAgain`, `Continue`. ### Clipboard changes WPF and Windows Forms now share the same clipboard API. `BinaryFormatter`-based clipboard methods are obsoleted; use JSON-based alternatives instead. ### Fluent style (in progress) .NET 10 expanded Fluent UI style support to additional controls: `DatePicker`, `GridSplitter`, `GridView`, `GroupBox`, `Hyperlink`, `Label`, `NavigationWindow`, `RichTextBox`, `TextBox`. Fluent style support is still incomplete; not all controls are covered yet. ### Performance improvements - Internal data structures replaced with `ReadOnlyCollection<T>` to reduce allocations. - Optimized font rendering, dynamic resources, XAML parsing, and cache operations. ### Removed legacy code Unused Code Access Security (CAS) code and XBAP-related code have been removed. Do not reference CAS APIs in .NET 10 WPF code. ## .NET 10 Runtime and SDK - JIT: improved inlining, method devirtualization, and stack allocation optimization. - AVX10.2 support added. - NativeAOT enhancements. - SDK: `dotnet test` now supports `Microsoft.Testing.Platform`; `dotnet tool exec` for one-shot tool execution. - Post-quantum cryptography: ML-DSA with HashML-DSA support, Composite ML-DSA, AES KeyWrap with Padding. - Networking: `WebSocketStream` API, TLS 1.3 on macOS. ## Guidance for Code Generation - Always use `net10.0-windows` as the target framework for WPF projects. - Use `<Nullable>enable</Nullable>` and `<ImplicitUsings>enable</ImplicitUsings>`. - Prefer the `field` keyword instead of explicit backing fields for simple validation cases. - Use the Grid inline syntax (`ColumnDefinitions="..."`) for conciseness. - Do not use `BinaryFormatter` for clipboard operations; use the new JSON-based clipboard APIs. - Do not reference CAS-related APIs (they have been removed). - C# 14 is the default language version when targeting .NET 10; no explicit `<LangVersion>` needed. ## Reference Links - [What's new in .NET 10](https://learn.microsoft.com/dotnet/core/whats-new/dotnet-10/overview) - [What's new in C# 14](https://learn.microsoft.com/dotnet/csharp/whats-new/csharp-14) - [What's new in WPF for .NET 10](https://learn.microsoft.com/dotnet/desktop/wpf/whats-new/net100)