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();
}