Converts an ECDSA signature in ASN.1/DER format (RFC 3279) to rs (IEEE P1363) format. For a definition of the ASN.1/DER format s. the accepted answer of this SO post:
https://crypto.stackexchange.com/questions/1795/how-can-i-convert-a-der-ecdsa-signature-to-asn-1
The conversion is done with public static byte[] ConvertFromASN1toRS(byte[] signatureASN1, int size). Here signatureASN1 is the byte array containing the signature in ASN.1/DER format and size is the key size (e.g. 32 bytes for P-256 aka prime256v1 aka secp256r1). The method returns a byte array containing the signature in rs format.
Note: C# supports the rs format and as of .NET 5.0 the ASN.1/DER format. BouncyCastle supports (in later versions) both formats (e.g. SHA1withECDSA and SHA1withPlainECDSA).