Decrypt MD5

Question

I have Encrypted a string in MD5 hash code
now I have to decrypt it please tell me

I am sending code of Encrypting

 string yourString = textBox3.Text;
            System.Security.Cryptography.MD5CryptoServiceProvider x = new System.Security.Cryptography.MD5CryptoServiceProvider();
            byte[] data = System.Text.Encoding.ASCII.GetBytes(yourString);
            data = x.ComputeHash(data);
            String md5Hash = System.Text.Encoding.ASCII.GetString(data);