i'm writing a script that resolve ip address for domain using C#
the problem is that i have a lot of domains that does not resolve to an IP, so the code (Dns.GetHostAddresses) is running for a long time trying to resolve an IP for a domain that doesn't have an IP.
this is the code:
public string getIPfromHost(string host)
{
try
{
var domain = Dns.GetHostAddresses(host)[0];
return domain.ToString();
}
catch (Exception)
{
return "No IP";
}
}
what i want to do is if there is no IP after 1 sec i want to return "No IP"
how can i achieve that?
You can achieve this by using TPL(Task Parallel Library). You can create new task and wait for 1 sec, if it is succeed then return true otherwise false.
just use below code in getIPfromHost(string host) this method.
(This is solution for your question which needs to wait for 1 sec please ensure your previous method was working fine.)
public string getIPfromHost(string host)
{
try
{
Task<string> task = Task<string>.Factory.StartNew(() =>
{
var domain = Dns.GetHostAddresses(host)[0];
return domain.ToString();
});
bool success = task.Wait(1000);
if (success)
{
return task.Result;
}
else
{
return "No IP";
}
}
catch (Exception)
{
return "No IP";
}
}
Related
My Xamarin Android app utilizes a Web service, which it connects to using HttpClient. On no connection (for exmaple when the user has no cell nor WiFi connection), an excpetion is thrown. I'm using async/await to get the data from the server. Here is an excerpt from my code:
public async Task<String> doLogin(string username, string password)
{
String url = Constants.loginEndpoint + username + "/" + password + "/";
var uri = new Uri(string.Format(url, string.Empty));
return_string = "";
try
{
var response = await GetAsync(uri);
if (response.IsSuccessStatusCode)
{
return_string = "success";
// Process the positive response here
else
{ }
}
catch (Exception ex)
{
throw new ConnectionException();
}
return return_string;
}
I defined a custon ConnectionException and want to show an AlertDialog to the user to inform them, that the request failed due to no connection. After the user clicks OK I want to close the app. I tried to show the alert dialog in the following way, but it's not working:
public class ConnectionException : Exception
{
public ConnectionException()
{
AlertDialog.Builder alert = new AlertDialog.Builder(myApp.Context);
alert.SetTitle("Failure");
alert.SetMessage("Request failed. No connection.");
alert.SetPositiveButton("OK", (senderAlert, args) =>
{
});
Dialog dialog = alert.Create();
dialog.Show();
}
public ConnectionException(string message)
: base(message)
{ }
public ConnectionException(string message, Exception innerException)
: base(message, innerException)
{ }
}
Is this the right approach? Probably not, as it's not working. I would appreciate any help on how to achieve this. Also, I've not given it too much thought, but is this a preferred way to handle such exceptions?
Assuming that your myApp.Context is an Activity and it has no back stack, you can just call Finish()
var context = myApp.Context; // this needs to be an Activity-based context...
context.RunOnUiThread(() =>
{
var alertDialog = new AlertDialog.Builder(context)
.SetTitle("Failure")
.SetMessage("Request failed. No connection.")
.SetPositiveButton("OK", (senderAlert, args) =>
{
context.Finish();
})
.Create();
alertDialog.Show();
});
Are you reusing this exception in several places, or is this a one off?
If your only using this exception once, there is no real reason to build your own.
You may as well just capture the exception and post your alert from inside your catch.
I know that's not as pretty of a way to write the catch, but if it works why not use it.
Side note:
DisplayAlert may be easier for you as well. It'll be a one liner.
Example:
await DisplayAlert("Failure","Request failed. No connection.", "Ok");
The way you are handling possible errors contains multiple issues and is not the right approach for several reasons.
First: Your code doesn't follow C-Sharp conventions and contains several code-smells. I show you a better and more accepted style.
1) Methods in C# normally starts with an uppercase letter. doLogin becomes Login
2) To create a new Uri instance you do not need to format your url-string. The string.Empty won't be used. So the code can be simplified into await GetAsync(new Uri(...));
3) The return_string seems not to be used in any way outside the method. It is string.Empty or "success". Why not switch it to bool? That way you can easily check if the login was successful. The return-type becomes bool instead of string.
The method looks now like this:
public async Task<bool> Login(string username, string password)
{
//TODO: Do parameter check for username and password
try
{
var response = await GetAsync(new Uri(Constants.loginEndpoint + username + "/" + password + "/"));
if (response.IsSuccessStatusCode)
{
// Process the positive response here
return true;
}
else
{
return false;
}
}
catch (Exception ex)
{
throw new ConnectionException();
}
return false;
}
Second, as mentioned by #Jason, an exception should not contain any UI or business logic. Consider the following, which will break your current implementation.
public async Task<bool> Login(string username, string password)
{
var connectionEx = new ConnectionException();
try
{
...
}
catch (Exception ex)
{
throw connectionEx;
}
...
}
Now your user will see the exception even so there wasn't any.
The last thing is that I recommend not to catch the exception just to throw your custom exception. The reason is, that there might be other things that raise an exception too. For example something is null in the positive response handling.
Depending on how the Login method is used, for example directly in an Android Activity, I would do something like that:
public async Task Login(string username, string password)
{
//TODO: Do parameter check for username and password
try
{
var response = await GetAsync(new Uri(Constants.loginEndpoint + username + "/" + password + "/"));
if (response.IsSuccessStatusCode)
{
// Process the positive response here
}
else
{
var alertDialog = new AlertDialog.Builder(context)
.SetTitle("Failure")
.SetMessage("Request failed.")
.SetPositiveButton("OK", (senderAlert, args) =>
{
Finish();
})
.Create();
alertDialog.Show();
}
}
catch (Exception ex)
{
var alertDialog = new AlertDialog.Builder(context)
.SetTitle("Failure")
.SetMessage("Something went wrong (" + ex.Message +")")
.SetPositiveButton("OK", (senderAlert, args) =>
{
Finish();
})
.Create();
alertDialog.Show();
}
}
What I want to happen: Pass the method a domain as a string and have it return true if the domain resolves. False if it does not. The underlying goal is to see if a domain exists.
What happens: Most valid domain strings return true. Some, however, return false despite resolving with nslookup.
I don't understand why certain domains are failing to resolve when they look fine when using command prompt nslookup and nslookup sites. (I've used https://centralops.net/ , http://www.kloth.net/services/nslookup.php , and http://network-tools.com/nslook/)
Method (C#):
//no blank domains
public bool CheckDomain(string sDomain)
{
if (string.IsNullOrWhiteSpace(sDomain)) return false;
for (int i = 1; i <= mQueryRetry; i++)
{
try
{
System.Net.IPAddress dnsCli = System.Net.IPAddress.Parse("8.8.8.8")
DnsClient myClient = new DnsClient(dnsCli);
DnsMessage dnsMessage = myClient.Resolve(ARSoft.Tools.Net.DomainName.Parse(sDomain), RecordType.A);
if ((dnsMessage == null) || ((dnsMessage.ReturnCode != ReturnCode.NoError) && (dnsMessage.ReturnCode != ReturnCode.NxDomain)))
{
throw new Exception("DNS request failed");
}
else
{
foreach (DnsRecordBase dnsRecord in dnsMessage.AnswerRecords)
{
ARecord aRecord = dnsRecord as ARecord;
if (aRecord != null)
{
return true;
}
}
}
}
catch (Exception ex)
{
// Back off and try again after 1 seconds
if (i != mQueryRetry)
{
System.Threading.Thread.Sleep(1000);
}
else
{
System.Diagnostics.Trace.WriteLine(string.Format("Domain: {0} error: {1}", sDomain, ex.Message));
}
}
}
System.Diagnostics.Trace.Flush();
return false;
}
If you plan to test it, I suggest replacing the dnsCli IPAddress with one of these. I've left the IP for the google DNS server in there as an example but I am using my company's DNS server in my production code. I've found that changing the DNS server in no way impacts the method's behavior.
I am using the latest version of Arsoft.Tools.Net (2.2.8) for the DnsClient, DnsMessage, DomainName, DnsRecordBase, and ARecord, classes/objects. We had the same problem with an older version (1.8.1).
Some of the domains that are failing to resolve are:
appraisallinks-amc.com
resurgenstech.com
orpheusvr.com
trovvit.com
Additional info: I've tried some ludicrously long query timeout limits, upwards of 5 minutes, and they made no difference. Therefore, I am certain that this is not a timeout issue.
"you can try and use a different library, the DnsClient (nuget) instead, see dnsclient.michaco.net. The domain names in question seem to work just fine " -
#MichaC
The problem was in fact the Arsoft.Tools.Net library I was using. Switching to DnsClient.Net fixed the problem.
I am working on ASP.NET web application (C# Language). One of my task is to send email to 1000 to 2000 person at a time.
I got problems like some end users(Email Receivers) got duplication multiple copies of same email content.
This method will call one by one as per new email address got from list. Due to privacy I remove some part of this method.
[System.Web.Services.WebMethod]
public static CampMaster SendMailContinue(int CustId)
{
try
{
Customers Customer = null;
Customer = Customers.GetbyCustNextId(CustId,true).FirstOrDefault();
string sTemplate = "Here will be Template content.";
#region SendMail
if (IsValidEmail(Customer.Email))
{
if (Globals.SendMail(sTemplate, FromEmailAddress, FromName, ToEmail,EmailSubject))
{
//Sent Success
}
}
sTemplate = string.Empty;
return true;
#endregion
}
}
catch (System.Threading.ThreadAbortException)
{
return null;
}
catch (Exception ex)
{
return null;
}
//Client Side Code by Call WebMethod.
function SendMailContinue(CustId, true) {
PageMethods.SendMailContinue(CustId, true, OnGetSuccessSendMailContinue, OnGetFailureSendMailContinue);
return false;
}
Is there a simple way of stopping a hangfire.io job from enqueuing if one is already enqueued?
Looking at the jobfilterattribute, nothing stands out as how to get the state of anything on the server. Can I use the connection objects and query the store?
Thanks
Have a look at the following gist by the library owner https://gist.github.com/odinserj/a8332a3f486773baa009
This should prevent the same job from being en-queued more than once by querying the fingerprint.
You can activate it per background job by decorating the method with the attribute [DisableMultipleQueuedItemsFilter].
Or you can enable it globally GlobalJobFilters.Filters.Add(new DisableMultipleQueuedItemsFilter());
I am using following code block to check to add new job or not, depending on its current state: (I know that i am currently looking at only first 1000 jobs. You can implement your type of logic))
private static bool IsOKToAddJob(string JobName, string QueueName, out string NotOKKey)
{
try
{
var monapi = JobStorage.Current.GetMonitoringApi();
var processingJobs = monapi.ProcessingJobs(0, 1000);
NotOKKey = processingJobs.Where(j => j.Value.Job.ToString() == JobName).FirstOrDefault().Key;
if (!string.IsNullOrEmpty(NotOKKey)) return false;
var scheduledJobs = monapi.ScheduledJobs(0, 1000);
NotOKKey = scheduledJobs.Where(j => j.Value.Job.ToString() == JobName).FirstOrDefault().Key;
if (!string.IsNullOrEmpty(NotOKKey)) return false;
var enqueuedJobs = monapi.EnqueuedJobs(QueueName, 0, 1000);
NotOKKey = enqueuedJobs.Where(j => j.Value.Job.ToString() == JobName).FirstOrDefault().Key;
if (!string.IsNullOrEmpty(NotOKKey)) return false;
NotOKKey = null;
return true;
}
catch (Exception ex)
{
//LOG your Exception;
}
}
And the usage is simple:
if (IsOKToAddJob(YOURJOBNAME, QueueName, out NOTOKKey))
var id = BackgroundJob.Enqueue(() =>YOURMETHOD());
//rest
I have an Excel Add-In written in C#, .NET 4.5. It will send many web service requests to a web server to get data. E.g. it sends 30,000 requests to web service server. When data of a request comes back, the addin will plot the data in Excel.
Originally I did all the requests asynchronously, but sometime I will get OutOfMemoryException
So I changed, sent the requests one by one, but it is too slow, takes long time to finish all requests.
I wonder if there is a way that I can do 100 requests at a time asynchronously, once the data of all the 100 requests come back and plot in Excel, then send the next 100 requests.
Thanks
Edit
On my addin, there is a ribbon button "Refresh", when it is clicked, refresh process starts.
On main UI thread, ribbon/button is clicked, it will call web service BuildMetaData,
once it is returned back, in its callback MetaDataCompleteCallback, another web service call is sent
Once it is returned back, in its callback DataRequestJobFinished, it will call plot to plot data on Excel. see below
RefreshBtn_Click()
{
if (cells == null) return;
Range firstOccurence = null;
firstOccurence = cells.Find(functionPattern, null,
null, null,
XlSearchOrder.xlByRows,
XlSearchDirection.xlNext,
null, null, null);
DataRequest request = null;
_reportObj = null;
Range currentOccurence = null;
while (!Helper.RefreshCancelled)
{
if(firstOccurence == null ||IsRangeEqual(firstOccurence, currentOccurence)) break;
found = true;
currentOccurence = cells.FindNext(currentOccurence ?? firstOccurence);
try
{
var excelFormulaCell = new ExcelFormulaCell(currentOccurence);
if (excelFormulaCell.HasValidFormulaCell)
{
request = new DataRequest(_unityContainer, XLApp, excelFormulaCell);
request.IsRefreshClicked = true;
request.Workbook = Workbook;
request.Worksheets = Worksheets;
_reportObj = new ReportBuilder(_unityContainer, XLApp, request, index, false);
_reportObj.ParseParameters();
_reportObj.GenerateReport();
//this is necessary b/c error message is wrapped in valid object DataResponse
//if (!string.IsNullOrEmpty(_reportObj.ErrorMessage)) //Clear previous error message
{
ErrorMessage = _reportObj.ErrorMessage;
Errors.Add(ErrorMessage);
AddCommentToCell(_reportObj);
Errors.Remove(ErrorMessage);
}
}
}
catch (Exception ex)
{
ErrorMessage = ex.Message;
Errors.Add(ErrorMessage);
_reportObj.ErrorMessage = ErrorMessage;
AddCommentToCell(_reportObj);
Errors.Remove(ErrorMessage);
Helper.LogError(ex);
}
}
}
on Class to GenerateReport
public void GenerateReport()
{
Request.ParseFunction();
Request.MetacompleteCallBack = MetaDataCompleteCallback;
Request.BuildMetaData();
}
public void MetaDataCompleteCallback(int id)
{
try
{
if (Request.IsRequestCancelled)
{
Request.FormulaCell.Dispose();
return;
}
ErrorMessage = Request.ErrorMessage;
if (string.IsNullOrEmpty(Request.ErrorMessage))
{
_queryJob = new DataQueryJob(UnityContainer, Request.BuildQueryString(), DataRequestJobFinished, Request);
}
else
{
ModifyCommentOnFormulaCellPublishRefreshEvent();
}
}
catch (Exception ex)
{
ErrorMessage = ex.Message;
ModifyCommentOnFormulaCellPublishRefreshEvent();
}
finally
{
Request.MetacompleteCallBack = null;
}
}
public void DataRequestJobFinished(DataRequestResponse response)
{
Dispatcher.Invoke(new Action<DataRequestResponse>(DataRequestJobFinishedUI), response);
}
public void DataRequestJobFinished(DataRequestResponse response)
{
try
{
if (Request.IsRequestCancelled)
{
return;
}
if (response.status != Status.COMPLETE)
{
ErrorMessage = ManipulateStatusMsg(response);
}
else // COMPLETE
{
var tmpReq = Request as DataRequest;
if (tmpReq == null) return;
new VerticalTemplate(tmpReq, response).Plot();
}
}
catch (Exception e)
{
ErrorMessage = e.Message;
Helper.LogError(e);
}
finally
{
//if (token != null)
// this.UnityContainer.Resolve<IEventAggregator>().GetEvent<DataQueryJobComplete>().Unsubscribe(token);
ModifyCommentOnFormulaCellPublishRefreshEvent();
Request.FormulaCell.Dispose();
}
}
on plot class
public void Plot()
{
...
attributeRange.Value2 = headerArray;
DataRange.Value2 = ....
DataRange.NumberFormat = ...
}
OutOfMemoryException is not about the too many requests sent simultaneously. It is about freeing your resources right way. In my practice there are two main problems when you are getting such exception:
Wrong working with immutable structures or System.String class
Not disposing your disposable resources, especially graphic objects and WCF requests.
In case of reporting, for my opinion, you got a second one type of a problem. DataRequest and DataRequestResponse are good point to start the investigation for the such objects.
If this doesn't help, try to use the Tasks library with async/await pattern, you can find good examples here:
// Signature specifies Task<TResult>
async Task<int> TaskOfTResult_MethodAsync()
{
int hours;
// . . .
// Return statement specifies an integer result.
return hours;
}
// Calls to TaskOfTResult_MethodAsync
Task<int> returnedTaskTResult = TaskOfTResult_MethodAsync();
int intResult = await returnedTaskTResult;
// or, in a single statement
int intResult = await TaskOfTResult_MethodAsync();
// Signature specifies Task
async Task Task_MethodAsync()
{
// . . .
// The method has no return statement.
}
// Calls to Task_MethodAsync
Task returnedTask = Task_MethodAsync();
await returnedTask;
// or, in a single statement
await Task_MethodAsync();
In your code I see a while loop, in which you can store your Task[] of size of 100, for which you can use the WaitAll method, and the problem should be solved. Sorry, but your code is huge enough, and I can't provide you a more straight example.
I'm having a lot of trouble parsing your code to figure out is being iterated for your request but the basic template for batching asynchronously is going to be something like this:
static const int batchSize = 100;
public async Task<IEnumerable<Results>> GetDataInBatches(IEnumerable<RequestParameters> parameters) {
if(!parameters.Any())
return Enumerable.Empty<Result>();
var batchResults = await Task.WhenAll(parameters.Take(batchSize).Select(doQuery));
return batchResults.Concat(await GetDataInBatches(parameters.Skip(batchSize));
}
where doQuery is something with the signature
Task<Results> async doQuery(RequestParameters parameters) {
//.. however you do the query
}
I wouldn't use this for a million requests since its recursive, but your case should would generate a callstack only 300 deep so you'll be fine.
Note that this also assumes that your data request stuff is done asynchronously and returns a Task. Most libraries have been updated to do this (look for methods with the Async suffix). If it doesn't expose that api you might want to create a separate question for how to specifically get your library to play nice with the TPL.