WebPart on Sharepoint downloads a file locally - I need to send it to the client

问题

please help me to Download file on the machine that use Sharepoint Site not the machine that has sharepoint server.

public class WebClientBL
{
    static WebClient client_ = new WebClient()
    {
        Credentials = CredentialCache.DefaultNetworkCredentials
    };

    public static void DownloadToClient(string path_in_sp, string path_in_local)
    {
        try
        {
            client_.DownloadFile(path_in_sp, path_in_local);
        }
        catch (Exception ex)
        {

        }
    }
}

来源：https://stackoverflow.com/questions/22659661/webpart-on-sharepoint-downloads-a-file-locally-i-need-to-send-it-to-the-client