C# 检测文件是否存在

• 本地文件是否存在

string curFile = @"c:\temp\test.txt";
Console.WriteLine(File.Exists(curFile) ? "File exists." : "File does not exist.");

• 网络文件是否存在

static async Task Main()
{
   // Create a New HttpClient object and dispose it when done, so the app doesn't leak resources
   using (HttpClient client = new HttpClient())
   {
      // Call asynchronous network methods in a try/catch block to handle exceptions
      try	
      {
         HttpResponseMessage response = await client.GetAsync("http://www.contoso.com/");
         response.EnsureSuccessStatusCode();
         string responseBody = await response.Content.ReadAsStringAsync();
         // Above three lines can be replaced with new helper method below
         // string responseBody = await client.GetStringAsync(uri);

         Console.WriteLine(responseBody);
      }  
      catch(HttpRequestException e)
      {
         Console.WriteLine("\nException Caught!");	
         Console.WriteLine("Message :{0} ",e.Message);
      }
   }
}

• 参考
  https://www.cnblogs.com/vaevvaev/p/7159427.html
  https://docs.microsoft.com/zh-cn/dotnet/api/system.net.http.httpclient?view=netframework-4.8