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‎.gitignore‎

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.vs
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bin
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obj

‎README.md‎

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# CronTimer
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Simple .net Timer that is based on cron expressions with second accuracy to fire timer events to a very specific schedule.
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Regular timers are very useful for tasks that do not really require any precision like polling a service at a rough interval but sometimes there is a need for more precision based on time. There is already a great time schedule expression syntax that originated from [Cron](https://en.wikipedia.org/wiki/Cron). Normally you would likely schedule such jobs via the operating system if they are things like on every Friday at 18:00 run a report but there are schedules that make more sense to have running in process like to not have a certain overhead of launching a whole job process or just because the process is already running. This small library makes it super easy to define such timers on a specific schedule.
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## Example
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Fire a timer event every 10 minutes from Monday through Friday between 8:00 and 17:00
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```
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var timer = new CronTimer("*/10 08-17 * * 1-5", "Europe/Amsterdam", includingSeconds: false);
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timer.OnOccurence += (s, ea) => Console.Out.WriteLineAsync(ea + " - " + DateTime.Now);
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timer.Start();
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```

‎src/CronTimer.cs‎

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using System;
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using System.Threading;
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using NCrontab;
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public class CronTimer
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{
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public const string UTC = "Etc/UTC";
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static readonly TimeSpan InfiniteTimeSpan = TimeSpan.FromMilliseconds(Timeout.Infinite); // net 3.5
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static readonly EventArgs ea = new EventArgs();
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readonly CrontabSchedule schedule;
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readonly TimeZoneInfo tzi;
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readonly string id;
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Timer t;
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public string tz { get; }
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public string Expression { get; }
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public event EventHandler<EventArgs> OnOccurence;
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public CronTimer(string expression, string tz = UTC, bool includingSeconds = false)
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{
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Expression = expression;
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this.tz = tz;
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id = TimeZoneConverter.TZConvert.IanaToWindows(tz);
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tzi = TimeZoneInfo.FindSystemTimeZoneById(id);
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schedule = CrontabSchedule.Parse(expression, new CrontabSchedule.ParseOptions { IncludingSeconds = includingSeconds });
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OnOccurence += OnOccurenceScheduleNext;
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}
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void OnOccurenceScheduleNext(object sender, EventArgs e)
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{
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var delay = CalculateDelay();
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//Console.WriteLine($"Next for [{tz} {expression}] in {delay}.");
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t.Change(delay, InfiniteTimeSpan);
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}
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public void Start()
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{
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var delay = CalculateDelay();
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//Console.WriteLine($"Next for [{tz} {expression}] in {delay}.");
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t = new Timer(s => OnOccurence(this, ea), null, delay, InfiniteTimeSpan);
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}
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TimeSpan CalculateDelay()
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{
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TimeSpan delay;
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if (tz != UTC)
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{
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var nowUtc = DateTime.UtcNow;
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var now = TimeZoneInfo.ConvertTimeFromUtc(nowUtc, tzi);
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var next = schedule.GetNextOccurrence(now);
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var nextUtc = next.ToUniversalTime();
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delay = nextUtc - nowUtc;
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}
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else
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{
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var nowUtc = DateTime.UtcNow;
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var nextUtc = schedule.GetNextOccurrence(nowUtc);
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delay = nextUtc - nowUtc;
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}
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//Console.WriteLine($"Now: {nowUtc} [utc] {now} [{tz}], Next: {next} [{tz}] {nextUtc} [utc], Delay: {delay}");
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if (delay < TimeSpan.Zero) delay = TimeSpan.Zero;
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return delay;
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}
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public void Stop()
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{
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t.Dispose();
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}
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}

‎src/CronTimer.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<LangVersion>latest</LangVersion>
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<TargetFrameworks>net35;netstandard2.1</TargetFrameworks>
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<PlatformTarget>AnyCPU</PlatformTarget>
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</PropertyGroup>
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<PropertyGroup>
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<!-- AssemblyFileVersionAttribute -->
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<FileVersion>1.0.0</FileVersion>
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<!-- AssemblyInformationalVersionAttribute -->
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<Version>$(FileVersion)</Version>
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<!-- AssemblyVersionAttribute -->
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<AssemblyVersion>1.0.0.0</AssemblyVersion>
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<!-- Nuget -->
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<PackageVersion>$(Version)</PackageVersion>
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<PackageId>CronTimer</PackageId>
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<Company>https://github.com/ramonsmits</Company>
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<Authors>ramonsmits</Authors>
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<Description>Simple .net Timer that is based on cron expressions with second accuracy to fire timer events to a very specific schedule.</Description>
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<PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
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<PackageReleaseNotes></PackageReleaseNotes>
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<PackageProjectUrl>https://github.com/ramonsmits/CronTimer/tree/$(PackageVersion)</PackageProjectUrl>
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<PackageLicenseExpression>MIT</PackageLicenseExpression>
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<IncludeSymbols>True</IncludeSymbols>
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<SymbolPackageFormat>snupkg</SymbolPackageFormat>
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<IncludeSource>True</IncludeSource>
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<RepositoryUrl>https://github.com/ramonsmits/CronTimer</RepositoryUrl>
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<Copyright>Copyright 2020 (c) Ramon Smits</Copyright>
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<PackageTags>cron timer</PackageTags>
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<GeneratePackageOnBuild>true</GeneratePackageOnBuild>
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<PublishRepositoryUrl>true</PublishRepositoryUrl>
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<ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
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<EmbedUntrackedSources>true</EmbedUntrackedSources>
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</PropertyGroup>
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<ItemGroup>
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<PackageReference Include="ncrontab" Version="[3.3.1, 4.0.0)" />
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<PackageReference Include="TimeZoneConverter" Version="[3.2.0, 4.0.0)" />
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</ItemGroup>
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<!--<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.1'">
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<PackageReference Include="Microsoft.Extensions.Logging.Abstractions">
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<Version>3.1.4</Version>
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</PackageReference>
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</ItemGroup>-->
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</Project>

‎src/CronTimer.sln‎

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Microsoft Visual Studio Solution File, Format Version 12.00
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# Visual Studio Version 16
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VisualStudioVersion = 16.0.30717.126
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MinimumVisualStudioVersion = 10.0.40219.1
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Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CronTimer", "CronTimer.csproj", "{FB64C227-8615-4AE1-94E3-F9F9DF192B72}"
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EndProject
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Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{CCDD0B34-653C-430C-9B17-5129618F8D7D}"
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ProjectSection(SolutionItems) = preProject
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..\README.md = ..\README.md
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EndProjectSection
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EndProject
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Global
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GlobalSection(SolutionConfigurationPlatforms) = preSolution
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Debug|Any CPU = Debug|Any CPU
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Release|Any CPU = Release|Any CPU
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EndGlobalSection
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GlobalSection(ProjectConfigurationPlatforms) = postSolution
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{FB64C227-8615-4AE1-94E3-F9F9DF192B72}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
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{FB64C227-8615-4AE1-94E3-F9F9DF192B72}.Debug|Any CPU.Build.0 = Debug|Any CPU
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{FB64C227-8615-4AE1-94E3-F9F9DF192B72}.Release|Any CPU.ActiveCfg = Release|Any CPU
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{FB64C227-8615-4AE1-94E3-F9F9DF192B72}.Release|Any CPU.Build.0 = Release|Any CPU
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EndGlobalSection
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GlobalSection(SolutionProperties) = preSolution
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HideSolutionNode = FALSE
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EndGlobalSection
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GlobalSection(ExtensibilityGlobals) = postSolution
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SolutionGuid = {A639B164-6581-40DF-ADC4-479DAB467CFE}
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EndGlobalSection
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EndGlobal

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