Big Breaking Changes in .NET 10

.NET 10 introduces several breaking changes developers should be aware of before upgrading. The IWebHost interface is now obsolete in favor of IHost, and projects should use WebApplication.CreateBuilder instead of WebHostBuilder. The new 'field' keyword can conflict with existing backing fields named 'field', requiring explicit 'this.field' or '@field' syntax. NuGet restore now audits transitive packages by default, which may fail builds when treating warnings as errors. System.Linq.Async is now built into the framework, eliminating the need for the separate NuGet package but potentially causing ambiguity in existing projects. Additional changes include implicit conversions for Span<T> and ReadOnlySpan<T>, and the new .slnx solution format.