dotnet-core/release-notes/2.1/Preview/api-diff/preview1/2.1-preview1_System.Numerics.md

System.Numerics

 namespace System.Numerics {
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
     public struct BigInteger : IComparable, IComparable<BigInteger>, IEquatable<BigInteger>, IFormattable {
+        public BigInteger(ReadOnlySpan<byte> value, bool isUnsigned=false, bool isBigEndian=false);
+        public int GetByteCount(bool isUnsigned=false);
+        public static BigInteger Parse(ReadOnlySpan<char> value, NumberStyles style=(NumberStyles)(7), IFormatProvider provider=null);
+        public byte[] ToByteArray(bool isUnsigned=false, bool isBigEndian=false);
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format=default(ReadOnlySpan<char>), IFormatProvider provider=null);
+        public static bool TryParse(ReadOnlySpan<char> value, NumberStyles style, IFormatProvider provider, out BigInteger result);
+        public static bool TryParse(ReadOnlySpan<char> value, out BigInteger result);
+        public bool TryWriteBytes(Span<byte> destination, out int bytesWritten, bool isUnsigned=false, bool isBigEndian=false);
     }
 }