如何在.net框架下将ECDiffieHellmanPublicKey实例转换为DER文件？

using System.Security.Cryptography;

ECDiffieHellman ecdh = ECDiffieHellman.Create();
byte[] publicKeyBytes = ecdh.PublicKey.ToByteArray();

byte[] derBytes = new byte[publicKeyBytes.Length + 24];
derBytes[0] = 0x30; // SEQUENCE tag
derBytes[1] = (byte)(publicKeyBytes.Length + 22); // Length of SEQUENCE
derBytes[2] = 0x30; // SEQUENCE tag for OID
derBytes[3] = 0x0A; // Length of OID
derBytes[4] = 0x06; // OID tag
derBytes[5] = 0x07; // Length of OID
derBytes[6] = 0x2A; // First part of OID (1.2)
derBytes[7] = 0x86; // Second part of OID (840)
derBytes[8] = 0x48; // Third part of OID (10045)
derBytes[9] = 0xCE; // Fourth part of OID (2)
derBytes[10] = 0x3D; // Fifth part of OID (3)
derBytes[11] = 0x02; // Sixth part of OID (2)
derBytes[12] = 0x01; // Seventh part of OID (1)
derBytes[13] = 0x06; // BIT STRING tag
derBytes[14] = (byte)(publicKeyBytes.Length + 1); // Length of BIT STRING
derBytes[15] = 0x04; // Uncompressed form
derBytes[16] = (byte)publicKeyBytes.Length; // Length of public key
Array.Copy(publicKeyBytes, 0, derBytes, 17, publicKeyBytes.Length);

string filePath = "publickey.der";
File.WriteAllBytes(filePath, derBytes);