using System.Net;
/// <summary>
/// 获得广播地址
/// </summary>
/// <param name="ipAddress">IP地址</param>
/// <param name="subnetMask">子网掩码</param>
/// <returns>广播地址</returns>
public static string GetBroadcast(string ipAddress, string subnetMask)
{

    byte[] ip = IPAddress.Parse(ipAddress).GetAddressBytes();
    byte[] sub = IPAddress.Parse(subnetMask).GetAddressBytes();

    // 广播地址=子网按位求反 再 或IP地址
    for (int i = 0; i < ip.Length; i++)
    {
        ip[i] = (byte)((~sub[i]) | ip[i]);
    }
    return new IPAddress(ip).ToString();
}

C#根据IP地址和子网掩码计算广播地址