dotnet-10

name	dotnet-10
description	Provides up-to-date knowledge about .NET 10 and C# 14 for WPF application development. Use this skill when developing WPF apps targeting .NET 10, or when asked about .NET 10 / C# 14 features.

.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

<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:

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:

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:

// 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

nameof(List<>)  // returns "List"

Lambda parameter modifiers without explicit types

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:

<!-- 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
• What's new in C# 14
• What's new in WPF for .NET 10