GetImage

check路径是是否有效，网络访问地址。notfound查找不到，httpstatuscode枚举数较多，根据自己想要的设置就好了。

public bool checkValid(string path)
        {
            HttpWebRequest request = HttpWebRequest.Create(path) as HttpWebRequest;
            request.Method = "GET";
            request.ProtocolVersion = new Version(1, 1);
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            if (response.StatusCode==HttpStatusCode.NotFound)
            {
                return false;
            }
            return true;
        }

根据网络地址还是本地路径，进行获取图片数据，保存到本地文件下。注意数据流的权限FileAccess.ReadWrite

保存有可能出错，在外层套了个try catch，不过各个节进行判断更好，能够拿到出错点。

if (url.IndexOf("http://") == 0 || url.IndexOf("https://") == 0)
                {
                    WebRequest request = (WebRequest)HttpWebRequest.Create(url);
                    WebResponse response = request.GetResponse();
                    Stream stream = response.GetResponseStream();
                    FileStream fileStream = File.Create(filePath);
                    byte[] buffer = new byte[(int)response.ContentLength];
                    int numReadByte = 0;
                    while ((numReadByte = stream.Read(buffer, 0, (int)response.ContentLength)) != 0)
                    {
                        fileStream.Write(buffer, 0, numReadByte);
                    }
                    fileStream.Close();
                    stream.Close();
                }
                else
                {
                    FileStream fs = File.Open(url, FileMode.Open, FileAccess.ReadWrite, FileShare.Read);
                    FileStream fileStream = File.Create(filePath);
                    Byte[] image = new Byte[(int)fs.Length];
                    int numReadByte = 0;
                    while ((numReadByte = fs.Read(image, 0, (int)fs.Length)) != 0)
                    {
                        fileStream.Write(image, 0, numReadByte);
                    }
                    fs.Close();
                    fileStream.Close();
                }