<PackageReference Include="System.Text.Json" Version="10.0.0-preview.7.25380.108" />

System.Text.ValueStringBuilder

namespace System.Text { internal ref struct ValueStringBuilder { public int Length { get; } public ValueStringBuilder(Span<char> initialBuffer); public ValueStringBuilder(int initialCapacity); public void Append(char c); public void Append(string s); public void Append(ReadOnlySpan<char> value); public void Dispose(); } }