<PackageReference Include="System.Diagnostics.DiagnosticSource" Version="11.0.0-preview.2.26159.112" />

System.StringPolyfills

static class StringPolyfills
namespace System { internal static class StringPolyfills { public static bool StartsWith(this string s, char value); public static bool EndsWith(this string s, char value); public static bool Contains(this string s, char value); } }