Phoenix.Data.Plc.Monitor.Polling 5.0.0

Phoenix.Data.Plc

Contains assemblies for communicating with a plc.

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Table of content

[toc]

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Usage

To get data from or write data to a plc, two things are needed.

• An instance of a specific IPlc.
• At least one IPlcItem.

The first is responsible for establishing the connection to the plc and how to read or write.
The later defines what kind of data and where to read it from or write it to the plc.

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IPlc Implementations

The following specific implementations for accessing a plc are currently available as separate NuGet packages:

Plc.Mock

.NET	.NET Standard	.NET Framework
✔️ 6 ✔️ 7	✔️ 2.0	✔️ 4.8

This provides a mocked plc, that stores its data in-memory. It can be used for test and simulation purposes.

Initialization

When creating an instance of the MockPlc class, initially available datablocks can be specified optionally. This implementation automatically creates or expands datablocks as they are accessed.

var initialDataBlocks = new Dictionary<ushort, byte[]>()
	{
		{65, new byte[] {0,1,2,3, 255} },
		{1245, new byte[] {0,1,2,3, 255} },
	};
IPlc plc = new MockPlc(initialDataBlocks);

❕ Like all other IPlc implementations this one has to be disposed once it is not used anymore.

Plc.AgLink

.NET	.NET Standard	.NET Framework
✔️ 6 ✔️ 7	✔️ 2.0	✔️ 4.8

This implementation utilizes the proprietary AGLink library owned by Delta Logic for communicating with the plc via S7 TCP/IP.

❕ AGLink is a commercial product owned by Delta Logic. Using the Plc.AgLink package requires their software, so make sure you are allowed to.

Build

❕ This repository does not contain the necessary AGLink libraries and auxiliary files needed to build the projects. Those files must be provided individually.

Plc.AgLink

To get the project Plc.AgLink to build, at least the .Net wrapper assembly AGL4DotNET.4.dll must be put into the ⬙\AgLink folder of the project. Optionally the AGL4DotNET.4.xml documentation file can be added too. Afterwards this project should be compilable. Bear in mind that the wrapper assembly will not be copied to the output folder during compilation, nor will it be part of the created NuGet package. Its only purpose within the Plc.AgLink project is to get it to properly build. Supplying all needed AGLink libraries and files must be done via other means. One way is described below.

Plc.AgLink.Demo

AGLink requires some additional files to properly run. The below table lists all those files.

File	Required	Origin	Description
AGL4DotNET.4.dll	✔️	AGLink package	.Net wrapper assembly
AGL4DotNET.4.xml	➖	AGLink package	.Net documentation file (can be omitted)
AGLink40.dll	✔️	AGLink package	Native connection assembly for 32 bit architecture
AGLink40_x64.dll	✔️	AGLink package	Native connection assembly for 64 bit architecture
AGLink40_Error.txt	➖	AGLink package	Contains error code to message mapping(can be omitted)
AGLink.license	❕	custom	Contains the license key (can, but shouldn't be omitted)

Prior to Phoenix.Data.Plc.AgLink v4.x those files where provided via a custom build target. The demo project Phoenix.Plc.AgLink.Demo contained an example how to do this in a custom project. This mechanism has been deprecated, because of the new way .Net 5 handles execution of applications published as single file. The result was a major change in the architecture of the AgLinkPlc class. Formerly this class was responsible for loading the unmanaged assemblies, the license key and even the error file. This no longer applies.

AgLinkPlc is now an abstract base class that has to be inherited by a custom class whose sole purpose should be, to provide the necessary files for AGLink to run. The proposed way of providing those files is creating a new project containing the inheriting class of AgLinkPlc along with all required files as an embedded resource of that assembly. The main Project Phoenix.Data.Plc.AgLink has two helper classes that have been created to help in this case.

The first is AgLinkRequirementsHelper which has the following static methods that should be called for providing the requirements:

•   static void CopyUnmanagedAssemblies(FileInfo assemblyFile, Stream assemblyContent)
  

  Copy the unmanaged assembly to the working directory. The unmanaged assembly will be deleted automatically once the application ends. This is done by AgLinkPlc.

• static bool ActivateAgLink(string? licenseKey)
  

  Provide the license key for activation. This can be omitted, in which case AGLink would operate in demo mode.

• static void OverrideErrorMapping(AgLinkErrorMapping agLinkErrorMapping)
  

  Override the default null-object error mapping. This can be omitted, in which case error codes from AGLink cannot be translated into readable messages.

The second one AgLinkPlcEmbeddedRequirementsHelper is for dealing with locating and extracting embedded resources from an assembly. It has the following static, but protected properties.

Those functions are protected as to not clutter IntelliSense with too much functions. Therefore AgLinkPlcEmbeddedRequirementsHelper must be inherited.

•   static ICollection<string> GetAlResourceNames(Assembly? assembly = null, bool writeNamesToDebug = false)
  

  Gets a list of all embedded resources of an assembly.

•   static string? LoadInternalResourceAsString(string? resourceName, Assembly? assembly = null)
  

  Loads the internal resource as a string. Can be used for the license key and the error messages.

•   static System.IO.Stream? LoadInternalResourceAsStream(string? resourceName, Assembly? assembly = null)
  

  Loads the internal resource as a stream. Can be used for the unmanaged assembly.

Like before the project Phoenix.Plc.AgLink.Demo shows an example on how best to setup a custom implementation where the required files are an embedded resources of the project. The new sub-class DemoAgLinkPlc in this project provides all requirements from its static constructor with the help of the above described AgLinkRequirementsHelper and a custom implementation of AgLinkPlcEmbeddedRequirementsHelper named DemoAgLinkPlcEmbeddedRequirementsHelper. Below is the code of both classes.

Here the DemoAgLinkPlc class provides the resources for AGLink:

public sealed class DemoAgLinkPlc : AgLinkPlc
{
	static DemoAgLinkPlc()
	{
		// Extract the unmanaged assembly.
		var (unmanagedAgLinkAssemblyFile, resourceStream) = DemoAgLinkPlcEmbeddedRequirementsHelper.LoadUnmanagedAssembly();
		AgLinkRequirementsHelper.CopyUnmanagedAssemblies(unmanagedAgLinkAssemblyFile, resourceStream);

		// Try to get the license key and activate AGLink.
		var licenseKey = DemoAgLinkPlcEmbeddedRequirementsHelper.LoadLicenseKey();
		AgLinkRequirementsHelper.ActivateAgLink(licenseKey);

		// Override error mapping from base class.
		var errorFileContent = DemoAgLinkPlcEmbeddedRequirementsHelper.LoadErrorMapping();
		AgLinkRequirementsHelper.OverrideErrorMapping(new AgLinkErrorMapping(errorFileContent));
	}
	
	/// <summary>
	/// Constructor
	/// </summary>
	/// <param name="connectionData"> <see cref="IAgLinkPlcConnectionData"/> </param>
	public DemoAgLinkPlc(IAgLinkPlcConnectionData connectionData)
		: base(connectionData) { }
}

DemoAgLinkPlcEmbeddedRequirementsHelper loads the embedded resources:

internal sealed class DemoAgLinkPlcEmbeddedRequirementsHelper : AgLinkPlcEmbeddedRequirementsHelper
{
	#region Properties

	/// <summary> The <see cref="Assembly"/> of the this class. </summary>
	private static Assembly CurrentAssembly { get; }

	/// <summary> The names of all embedded resources of this assembly. Obtained via <see cref="AgLinkPlcEmbeddedRequirementsHelper.GetAlResourceNames"/>. </summary>
	private static ICollection<string> ResourceNames { get; }
	
	#endregion

	#region (De)Constructors

	static DemoAgLinkPlcEmbeddedRequirementsHelper()
	{
		CurrentAssembly = Assembly.GetExecutingAssembly();
		ResourceNames = AgLinkPlcEmbeddedRequirementsHelper.GetAlResourceNames(CurrentAssembly);
	}

	#endregion

	#region Methods

	/// <summary>
	/// Loads the embedded unmanaged assembly.
	/// </summary>
	/// <param name="is64BitProcess"> Optional boolean if the 64-bit version of the unmanaged assembly should be loaded. By default this is determined by <see cref="Environment.Is64BitProcess"/>. </param>
	/// <returns> The file name of the unmanaged assembly and its content as a <see cref="Stream"/> reset to <see cref="SeekOrigin.Begin"/>. This stream is not closed and needs to be disposed! </returns>
	internal static (string FileName, Stream? ResourceStream) LoadUnmanagedAssembly(bool? is64BitProcess = null)
	{
		is64BitProcess ??= Environment.Is64BitProcess;
		var currentAssembly = DemoAgLinkPlcEmbeddedRequirementsHelper.CurrentAssembly;
		var resourceNames = DemoAgLinkPlcEmbeddedRequirementsHelper.ResourceNames;
		var unmanagedAssemblyFileName = $"AGLink40{(is64BitProcess.Value ? "_x64" : "")}.dll";
		var resourceName = resourceNames.FirstOrDefault(name => name.ToLower().Contains(unmanagedAssemblyFileName.ToLower()));
		var resourceStream = AgLinkPlcEmbeddedRequirementsHelper.LoadInternalResourceAsStream(resourceName, currentAssembly);
		if (resourceStream?.CanSeek ?? false) resourceStream.Seek(0, SeekOrigin.Begin);
		return (unmanagedAssemblyFileName, resourceStream);
	}

	/// <summary>
	/// Loads the embedded license key.
	/// </summary>
	/// <returns> The license key or null. </returns>
	internal static string? LoadLicenseKey()
	{
		var currentAssembly = DemoAgLinkPlcEmbeddedRequirementsHelper.CurrentAssembly;
		var resourceNames = DemoAgLinkPlcEmbeddedRequirementsHelper.ResourceNames;
		var licenseFileName = "AGLink.license";
		var resourceName = resourceNames.FirstOrDefault(name => name.ToLower().Contains(licenseFileName.ToLower()));
		var licenseKey = AgLinkPlcEmbeddedRequirementsHelper.LoadInternalResourceAsString(resourceName, currentAssembly);
		return licenseKey;
	}

	/// <summary>
	/// Loads the embedded error file.
	/// </summary>
	/// <returns> The error file as single string or null. </returns>
	internal static string? LoadErrorMapping()
	{
		var currentAssembly = DemoAgLinkPlcEmbeddedRequirementsHelper.CurrentAssembly;
		var resourceNames = DemoAgLinkPlcEmbeddedRequirementsHelper.ResourceNames;
		var errorFileName = "AGLink40_Error.txt";
		var resourceName = resourceNames.FirstOrDefault(name => name.ToLower().Contains(errorFileName.ToLower()));
		var errorFileContent = AgLinkPlcEmbeddedRequirementsHelper.LoadInternalResourceAsString(resourceName, currentAssembly);
		return errorFileContent;
	}

	#endregion
}

Initialization

To create an instance of any AGLinkPlc class, the AgLinkPlcConnectionData has to be supplied. It basically contains the IP address and some additional information about the plc.

var connectionData = new AgLinkPlcConnectionData(deviceNumber: 0, ip: "127.0.0.2", rack: 0, slot: 0);
IPlc plc = new DemoAgLinkPlc(connectionData);

<div style='padding:0.1em; border-style: solid; border-width: 0px; border-left-width: 10px; border-color: #37ff00; background-color: #37ff0020' > <span style='margin-left:1em; text-align:left'> <b>Information</b> </span> <br> <div style='margin-left:1em; margin-right:1em;'> Like all other <i>IPlc</i> implementations this one has to be disposed once it is not used anymore. </div> </div>

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PlcItems

An IPlcItem contains all data needed to read or write to the plc.

Property	Data Type	Description
Type	Enum PlcItemType	Input, Output, Flags, Data
DataBlock	UInt16	The datablock of the item. This is 0 for all types except PlcItemType.Data.
Position	UInt16	The zero-based byte-position.
BitPosition	Enum BitPosition	X0, X1, ... , X7
Value	BitCollection	Specialized class that holds the bits and bytes of the item.

To make working with plc items easier, specialized items for the most common data types exist in the namespace Phoenix.Data.Plc.Items.Typed. Those items automatically convert the underlying BitCollection into more specific types. A hopefully complete list of all available items can be found here.

Initialization

Creating a new IPlcItem can be done either by using the constructor of any specific item or more guided via builder pattern.

Constructor

var item = new Utf8PlcItem(0, 4, 10, identifier: "UTF-8");

Builder

var itemBuilder = new Phoenix.Data.Plc.Items.Builder.PlcItemBuilder();
var item = itemBuilder
	.ConstructUtf8PlcItem("UTF-8")
	.AtDatablock(0)
	.AtPosition(4)
	.WithLength(10)
	.Build()
	;

Reading / Writing plc items

Reading or writing is done via the following methods of any IPlc instance:

Read a collection of IPlcItem's from the plc.

Task ReadItemsAsync(ICollection<IPlcItem> plcItems, CancellationToken cancellationToken = default)

Write a collection of IPlcItem's to the plc.

Task<bool> WriteItemsAsync(ICollection<IPlcItem> plcItems, CancellationToken cancellationToken = default)

As to not pollute the IPlc interface with unnecessary methods, some extension methods for other common read or write operations are provided via the PlcExtensions class:

Read a single IPlcItem from the plc.

Task<TValue> ReadItemAsync<TValue>(this IPlc plc, IPlcItem<TValue> plcItem, CancellationToken cancellationToken = default)

Task<BitCollection> ReadItemAsync(this IPlc plc, IPlcItem plcItem, CancellationToken cancellationToken = default)

Write a single IPlcItem's to the plc.

Task<bool> WriteItemAsync(this IPlc plc, IPlcItem plcItem, CancellationToken cancellationToken = default)

Write a single or multiple IPlcItem's to the plc and validate the result.

Task<bool> WriteItemWithValidationAsync(this IPlc plc, IPlcItem plcItem, CancellationToken cancellationToken = default)

Task<bool> WriteItemsWithValidationAsync(this IPlc plc, ICollection<IPlcItem> plcItems, CancellationToken cancellationToken = default)

Read or write errors

Reading or writing can throw a ReadOrWritePlcException that should be handled by consuming code. This exception contains two collections identifying which items succeeded and which failed:

• ValidItems: This is a pure collection of IPlcItemsthat succeeded.
• FailedItems: This is a tuple containing the failed IPlcItemtogether with an error message.

<div style='padding:0.1em; border-style: solid; border-width: 0px; border-left-width: 10px; border-color: #ff0000; background-color: #ff000020' > <span style='margin-left:1em; text-align:left'> <b>Warning</b> </span> <br> <div style='margin-left:1em; margin-right:1em;'> Trying to read or write anything to/from an <i>IPlc</i> inheriting from the <i>Plc</i> base class that is currently <b>not connected</b>, will not fail. Rather all <i>IPlcItems</i> that are affected will be put on hold until the connection has been established. This means that calling <i>await plc.ReadItemsAsync(...)</i> or <i>await plc.WriteItemsAsync(...)</i> won't return until the connection is up and running. </div> </div>

<div style='padding:0.1em; border-style: solid; border-width: 0px; border-left-width: 10px; border-color: #ff0000; background-color: #ff000020' > <span style='margin-left:1em; text-align:left'> <b>Warning</b> </span> <br> <div style='margin-left:1em; margin-right:1em;'> Trying to read or write anything to/from an <i>IPlc</i> inheriting from the <i>Plc</i> base class that has been disposed will result in a <i>ReadOrWritePlcException</i>. The same goes for read or write operations whose <i>IPlcItems</i> have been put on hold. </div> </div>

Typed plc items

Data plc items

• BitPlcItem

  Has an extension method SetValue that allows to use a string for setting the value of the item. Every value except the following will be treated as false (comparison is case-insensitive): true, yes, ok, 1.

• BitsPlcItem

• BytePlcItem

• BytesPlcItem

  Has an extension method SetValue that allows to use a string in Hex or byte array format for setting the value of the item. Acceptable string values are:

  • HEX
    • Can be prefixed with either 0x, # or nothing.
    • The values can be chained together or separated by either , ; - or whitespace.
  • Bytes
    • No prefix allowed here.
    • The values must be separated by either , ; - or whitespace.

• DynamicBytesPlcItem (see DynamicPlcItems for more information)

Numeric plc items

• Int16PlcItem
• Int32PlcItem
• Int64PlcItem
• UInt16PlcItem
• UInt32PlcItem
• UInt64PlcItem
• WordPlcItem
• DWordPlcItem
• LWordPlcItem

Text plc items

Those items typically inherit from TextPlcItem and provide different text encodings.

• Utf8PlcItem
• DynamicUtf8PlcItem (see DynamicPlcItems for more information)

Other plc items

• EnumPlcItem

DynamicPlcItems

Those are special PlcItems that can be used for dynamic data where the length of the item is not known during design time but rather encoded within the first few bytes of the item itself. A typical usage scenario are strings of different sizes, where the actual string length is the first byte of the item itself.

Each IDynamicPlcItem internally consists of two separate PlcItems.

LengthPlcItem	This is the item whose value is the actual length of the second item. The LengthPlcItem itself has a fixed size and must be an INumericPlcItem.
FlexiblePlcItem	This is the item whose length is dynamic. It can be any normal IPlcItem but actually only BytesPlcItem and TextPlcItem are currently implemented as dynamic items.

Reading and writing an IDynamicPlcItem always consists of two steps. When reading such an item the LengthPlcItem will be read first to obtain the current length and afterwards the data of the FlexiblePlcItem is obtained. Writing is the opposite.

<div style='padding:0.1em; border-style: solid; border-width: 0px; border-left-width: 10px; border-color: #ffd200; background-color: #ffd20020' > <span style='margin-left:1em; text-align:left'> <b>Hint</b> </span> <br> <div style='margin-left:1em; margin-right:1em;'> Since reading and writing is done in two steps, it cannot be guaranteed, that the data of an IDynamicPlcItem is consistent. </div> </div>

Dynamic items additionally provide some special properties that may come in handy under certain conditions.

LengthFactor	This factor will be applied to the length of a dynamic item. It should be used if the LengthPlcItem does not provide an absolute byte amount, but rather an amount of items.
LengthLimit	This is an optional limit that will be applied to the length being read or written.

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PlcMonitor

Sometimes it may be necessary to monitor data within a plc and react if this data changes. This can be done with one of the specific IPlcMonitor Implementations. The IPlcMonitor can be used on its own, or wrapped together with an IPlc as an IMonitorablePlc. Later should be used, if monitoring data is done regularly. This way the two dependencies IPlc and IPlcMonitor can be replaced by just a single IMonitorablePlc.

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IPlcMonitor Implementations

PollingPlcMonitor

.NET Framework	.NET Standard	.NET
✔️ 4.5.0	✔️ 2.0	✔️ 5.0

This monitor internally uses an IPlc and regularly polls monitored IPlcItems and checks if their data has changed. It provides the PollingMonitorablePlc wrapper class that combines both the plc and the monitor instance.

Polling Frequency

The frequency at witch IPlcItems are polled has a default value of 300 milliseconds. This is defined by PlcItemMonitorConfigurations.DefaultPollingFrequency. Although this interval should be sufficient enough for most cases, it can be changed to a different value.

❕ Changing the default monitoring frequency does not change the interval at which already monitored items are polled.
❕ The minimum polling frequency is 50 milliseconds and cannot be undershot.

In case the normal frequency is good enough expect for some critical items, the PollingPlcMonitor accepts special PlcItemMonitorConfigurations that define different frequencies for named IPlcItems. A single PlcItemMonitorConfiguration for an IPLcItem simply consists of the IPlcItem.Identifier and a custom polling interval that will be applied to the it. The PlcItemMonitorConfigurations are implicitly convertible from a Dictionary<string, uint>, so it is possible to pass one such dictionary to the constructor of the PollingPlcMonitor. This is done so custom configuration can be stored externally (in some kind of settings file) without the storage provider needing to know anything about the special configuration classes.

Initialization

Create a new PollingPlcMonitor instance.

IPlc plc = new IPlc();
IPlcMonitor plcMonitor = new PollingPlcMonitor(plc);

Create a new PollingMonitorablePlc instance.

IPlc plc = new IPlc();
IMonitorablePlc monitoredPlc = new PollingMonitorablePlc(plc);

Create a new PollingMonitorablePlc instance via fluent syntax.

IMonitorablePlc monitoredPlc = new IPlc().MakeMonitorable();

Create a new PollingMonitorablePlc instance via fluent syntax and custom polling frequency configuration.

IMonitorablePlc monitoredPlc = new MockPlc().MakeMonitorable
	(
		new Dictionary<string, uint>
		{
			{"FastItem", 200},
			{"LightspeedItem", 50},          
			{"SlowItem", 1000},
		}
	);

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Logging

The Phoenix.Data.Plc package provides its own small logging facility in form the ILogger interface and the static LogManager which is internally used to provide specific logger instances. Via the static property LogManager.LoggerFactory the kind of provided ILogger can be changed externally.

// Create a custom ILogger instance and let the log manager use it.
Phoenix.Data.Plc.Logging.ILogger logger = new ...
Phoenix.Data.Plc.Logging.LogManager.LoggerFactory = () => logger;

Phoenix.Data.Plc comes with the following ILogger implementations:

• NullLogger: An implementation that does nothing. This is the default.
• TraceLogger: An implementation that uses System.Diagnostics.Trace to output log messages.

The LogManager has another static property LogAllReadAndWriteOperations which instructs the Plc base class to log all read and write operations. This is disabled by default, as it could be a very costly operation depending on the amount of operations.

// Conditionally log all read and write operations of the plc.
#if DEBUG
	Phoenix.Data.Plc.Logging.LogManager.LogAllReadAndWriteOperations = true;
#else
	Phoenix.Data.Plc.Logging.LogManager.LogAllReadAndWriteOperations = false;
#endif

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Helper

The Phoenix.Data.Plc.Mock package contains a static helper class ByteArrayExtensions that provides some extensions methods build to help manipulating data with byte arrays. Basically those methods allow for automatically converting basic data types into byte data and then writing this data to any byte array. For values that surpass the size of a single byte, the corresponding endianness has to be specified.

The following functions are available:

// Applies a boolean array.
var data = new byte[45];
var booleans = new bool[] { true, true, false, false };
data.ApplyValue(bytePosition: 10, booleans);
data.ApplyValue(bytePosition: 10, bitPosition: BitPosition.X3, booleans);

// Applies a byte.
var data = new byte[45];
var @byte = byte.MaxValue;
data.ApplyValue(bytePosition: 10, @byte);

// Applies another byte array.
var data = new byte[45];
var bytes = new byte[] {byte.MaxValue, byte.MaxValue};
data.ApplyValue(bytePosition: 10, bytes);

// Applies a short (Int16).
var data = new byte[45];
var @short = Int16.MinValue;
data.ApplyValue(bytePosition: 10, @short, DataConverter.Endianness.BigEndian);

// Applies an ushort (UInt16).
var data = new byte[45];
var @ushort = UInt16.MaxValue;
data.ApplyValue(bytePosition: 10, @ushort, DataConverter.Endianness.LittleEndian);

// Applies an int (Int32).
var data = new byte[45];
var @int = Int32.MinValue;
data.ApplyValue(bytePosition: 10, @int, DataConverter.Endianness.BigEndian);

// Applies an uint (UInt32).
var data = new byte[45];
var @uint = UInt32.MaxValue;
data.ApplyValue(bytePosition: 10, @uint, DataConverter.Endianness.LittleEndian);

// Applies a long (Int64).
var data = new byte[45];
var @long = Int64.MinValue;
data.ApplyValue(bytePosition: 10, @long, DataConverter.Endianness.BigEndian);

// Applies an ulong (UInt64).
var data = new byte[45];
var @ulong = UInt64.MaxValue;
data.ApplyValue(bytePosition: 10, @ulong, DataConverter.Endianness.LittleEndian);

// Applies a string.
var data = new byte[45];
var @string = "Foo";
data.ApplyValue(bytePosition: 10, @string, Encoding.ASCII);

Those methods directly operate on the original byte array and additionally also return it back to the caller which allows for chaining multiple commands.

var data = new byte[45]
	.ApplyValue(bytePosition: 10, value: ushort.MaxValue, DataConverter.Endianness.BigEndian)
	.ApplyValue(bytePosition: 15, value: long.MaxValue, DataConverter.Endianness.LittleEndian)
	.ApplyValue(bytePosition: 30, value: "Bar", Encoding.ASCII)
	;

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Authors

• Felix Leistner: v1.x - v5.x