TIA Portal Openness C# — Common Foundation

Source: TIA Portal Openness General Functions Manual (03/2026, V21); V21 IntelliSense XML documentation files (PublicAPI\V21\net48*.xml)

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V21 modular assembly architecture

V21 splits the API across multiple DLLs instead of a single Siemens.Engineering.dll. Every project needs Siemens.Engineering.Base.dll; add domain DLLs as required. Referencing the wrong DLL (or omitting one) causes TypeLoadException at runtime.

Full mapping: See references/assembly-namespace-map.md for the V21 namespace → DLL → domain skill table, cross-assembly warnings, and csproj patterns.

Namespaces by assembly

Only import what is actually used. The list below covers the most commonly needed namespaces. The mapping file summarizes the XML-documented namespaces across all 16 installed V21 PublicAPI DLLs.

Siemens.Engineering.Base.dll (always required):

using Siemens.Engineering;                          // TiaPortal, Project, ExclusiveAccess, Transaction, events, exceptions
using Siemens.Engineering.Compiler;                 // CompilerResult
using Siemens.Engineering.Compare;                  // CompareResult
using Siemens.Engineering.Connection;               // connection objects between devices
using Siemens.Engineering.CrossReference;            // cross-reference queries
using Siemens.Engineering.Download;                 // DownloadProvider, DownloadConfiguration
using Siemens.Engineering.Download.Configurations;  // device-specific download configs (★ also in Step7 + Startdrive)
using Siemens.Engineering.HW;                       // Device, DeviceItem, Subnet, Node, IoSystem (★ also in Step7)
using Siemens.Engineering.HW.CommunicationConnections; // communication connection configs
using Siemens.Engineering.HW.Extensions;            // extension methods on HW objects
using Siemens.Engineering.HW.Features;              // SoftwareContainer, NetworkInterface (★ also in Step7)
using Siemens.Engineering.HW.HardwareCatalog;       // hardware catalog access
using Siemens.Engineering.HW.Utilities;             // HW utility helpers
using Siemens.Engineering.Library;                  // ProjectLibrary, GlobalLibrary
using Siemens.Engineering.Library.MasterCopies;     // MasterCopy, MasterCopyFolder
using Siemens.Engineering.Library.Types;            // LibraryType, LibraryTypeVersion
using Siemens.Engineering.Multiuser;                // LocalSession, ProjectServer
using Siemens.Engineering.Online;                   // OnlineProvider, OnlineState
using Siemens.Engineering.Online.Configurations;    // OnlineConfiguration, TLS/authentication callbacks
using Siemens.Engineering.Security;                 // SecurityController, certificates
using Siemens.Engineering.Settings;                 // TIA Portal settings
using Siemens.Engineering.Umac;                     // UmacRole, UmacUser, UmacFunctionRight
using Siemens.Engineering.Upload;                   // StationUploadProvider, ParameterUploadProvider
using Siemens.Engineering.Upload.Configurations;    // upload configs (★ also in Startdrive)
using Siemens.Engineering.VersionControl;           // workspace and version control providers

Siemens.Engineering.Step7.dll (PLC operations):

using Siemens.Engineering.Cax;                      // CAx import/export
using Siemens.Engineering.SW;                       // PlcSoftware
using Siemens.Engineering.SW.Alarm;                 // PlcAlarm, AlarmClass
using Siemens.Engineering.SW.Alarm.TextLists;       // alarm text lists
using Siemens.Engineering.SW.Blocks;                // PlcBlock, OB, FB, FC, GlobalDB, InstanceDB, ArrayDB
using Siemens.Engineering.SW.Blocks.Interface;      // block interface access
using Siemens.Engineering.SW.ExternalSources;       // PlcExternalSource
using Siemens.Engineering.SW.Loader;                // program loader
using Siemens.Engineering.SW.OpcUa;                 // OPC UA server interface
using Siemens.Engineering.SW.Supervision;           // supervision alarms, operator messages
using Siemens.Engineering.SW.Tags;                  // PlcTagTable, PlcTag, PlcConstant
using Siemens.Engineering.SW.TechnologicalObjects;  // technology objects
using Siemens.Engineering.SW.TechnologicalObjects.Motion; // motion axes (★ also in Startdrive)
using Siemens.Engineering.SW.Types;                 // PlcType, PlcStruct
using Siemens.Engineering.SW.Units;                 // SoftwareUnit, CodeBlock, DataBlock
using Siemens.Engineering.SW.WatchAndForceTables;   // PlcWatchTable, PlcForceTable

Siemens.Engineering.WinCC.dll (classic HMI):

using Siemens.Engineering.Hmi;                      // HmiTarget (★ also in WinCC.Extension)
using Siemens.Engineering.Hmi.Alarm;                // DiscreteAlarm, AnalogAlarm
using Siemens.Engineering.Hmi.Communication;        // HmiConnection
using Siemens.Engineering.Hmi.Cycle;                // cycle settings
using Siemens.Engineering.Hmi.Dynamic;              // dynamization
using Siemens.Engineering.Hmi.Faceplate;            // faceplate types
using Siemens.Engineering.Hmi.Globalization;         // language/translation
using Siemens.Engineering.Hmi.Logging;              // DataLog, LoggingTag
using Siemens.Engineering.Hmi.Recipe;               // Recipe, RecipeElement
using Siemens.Engineering.Hmi.RuntimeScripting;     // VBScript
using Siemens.Engineering.Hmi.Screen;               // HmiScreen, ScreenTemplate, ScreenPopup + all elements
using Siemens.Engineering.Hmi.Tag;                  // HmiTag, HmiTagTable
using Siemens.Engineering.Hmi.TextGraphicList;      // text/graphic lists
using Siemens.Engineering.Hmi.Theming;              // HMI themes

Siemens.Engineering.Startdrive.dll (SINAMICS drives):

using Siemens.Engineering.MC.Drives;                // DriveObject, DriveParameter, Telegram
using Siemens.Engineering.MC.Drives.DFI;            // DriveFunctionInterface, Commissioning
using Siemens.Engineering.MC.Drives.Enums;          // drive enumerations
using Siemens.Engineering.MC.Drives.SecurityObjects; // drive encryption, UMAC

Siemens.Engineering.Safety.dll (F-system):

using Siemens.Engineering.Safety;                   // safety operations

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Assembly loading — mandatory for standalone Openness apps

Not needed for Add-Ins. TIA Portal loads Add-In assemblies via its own loader. This section applies only to standalone console/desktop Openness applications.

V21 installation paths

• Registry key: HKLM\SOFTWARE\Siemens\Automation\InstalledApps\Totally Integrated Automation Portal V21 → value INSTALLPATH
• Binary path: C:\Program Files\Siemens\Automation\Portal V21\PublicAPI\V21\net48\
• Manifest schemas: C:\Program Files\Siemens\Automation\Portal V21\PublicAPI\V21\Schemas\

Resolver pattern

When using the AssemblyResolve approach, register the event before any Openness type is referenced. This includes method parameters, return types, and class properties — not just method bodies. A correctly configured app.config binding is an alternative.

Recommended pattern: register in a static constructor of Program, then move all Openness code to a separate class so the resolver is active before those classes are loaded.

internal static class Program
{
    // Register resolver at earliest possible point
    static Program()
    {
        AppDomain.CurrentDomain.AssemblyResolve += OnAssemblyResolve;
    }

    public static void Main()
    {
        // All Openness code must be in a separate class
        var app = new OpennessApp();
        app.Run();
    }

    private static Assembly OnAssemblyResolve(object sender, ResolveEventArgs args)
    {
        // Read install path from registry (recommended) or hardcode for simple tools
        string opennessFolder = GetOpennessInstallPath(); // implement per project
        AssemblyName requestedName = new AssemblyName(args.Name);
        string filePath = Path.Combine(opennessFolder,
            string.Concat(requestedName.Name, ".dll"));

        if (!requestedName.Name.StartsWith("Siemens.Engineering.") ||
            !File.Exists(filePath))
            return null;

        Assembly loaded = Assembly.LoadFrom(filePath);
        if (requestedName.FullName != loaded.GetName().FullName)
            throw new FileNotFoundException(
                "TIA Portal Openness version does not match", filePath);

        return loaded;
    }
}

Key rules:

• Copy Local: False (<Private>False</Private>) must be set for every Siemens.Engineering assembly reference.
• V21 uses modular DLLs: Base.dll is always needed; add Step7.dll, WinCC.dll, Startdrive.dll, etc. per task. The resolver handles all of them automatically because it matches any name starting with Siemens.Engineering..
• The recommended approach reads the install path from the registry key HKLM\SOFTWARE\Siemens\Automation\InstalledApps\Totally Integrated Automation Portal V21 (value INSTALLPATH) rather than hardcoding it.

Registry-based path discovery:

private static string GetOpennessInstallPath()
{
    using (var key = Microsoft.Win32.Registry.LocalMachine.OpenSubKey(
        @"SOFTWARE\Siemens\Automation\InstalledApps\Totally Integrated Automation Portal V21"))
    {
        string installPath = key?.GetValue("INSTALLPATH") as string;
        if (string.IsNullOrEmpty(installPath))
            throw new FileNotFoundException("TIA Portal V21 installation not found in registry.");
        return Path.Combine(installPath, @"PublicAPI\V21\net48");
    }
}

Alternative — app.config: For stable installations where the path is known at build time, an app.config file with <assemblyBinding> / <codeBase> entries is a simpler option that requires no code. Use the AssemblyResolve event for tools that need to discover the install path at runtime.

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TiaPortal instantiation

Always use a using statement so the session is disposed on exit or exception:

internal class OpennessApp
{
    public void Run()
    {
        using (TiaPortal tiaPortal = new TiaPortal(TiaPortalMode.WithUserInterface))
        {
            // All Openness work goes here
        }
        // TIA Portal is disposed (not necessarily closed) after this point
    }
}

Modes:

• TiaPortalMode.WithUserInterface — starts a new TIA Portal instance with a visible GUI
• TiaPortalMode.WithoutUserInterface — starts a new headless instance, suitable for automation pipelines

Attaching to a running instance:

// Attach to the first running TIA Portal process of this Openness version
TiaPortal tiaPortal = TiaPortal.GetProcesses().First().Attach();

Use GetProcesses() when TIA Portal is already open and you do not want to start a new instance. Returns only processes from the same Openness version as the loaded assembly.

Dispose vs. close:

• If started headless and no other Openness client is attached, Dispose() closes TIA Portal.
• If started with GUI or other clients are attached, Dispose() only disconnects.
• After disposal, the connection is no longer valid. A later API call after the TIA Portal process is closed externally throws NonRecoverableException.

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Service providers — GetService<T>()

V21 uses a service-provider pattern for UI interactions. Call GetService<T>() on the TiaPortal instance to obtain a service. Available services depend on the runtime context.

Add-In runtime services

These services are available only when code runs inside a TIA Portal Add-In:

Service type	Namespace	Purpose
MessageBoxProvider	Siemens.Engineering.AddIn	Display notification/confirmation dialogs in TIA Portal
ProgressProvider	Siemens.Engineering.AddIn	Display a progress bar; check IsCancelRequested for cancellation
FeedbackProvider	Siemens.Engineering.AddIn	Log messages to TIA Portal's Inspector window (General Info tab)

// MessageBoxProvider — notification and confirmation dialogs
var msgBox = tiaPortal.GetService<MessageBoxProvider>();
msgBox?.ShowNotification(NotificationIcon.Information, "Title", "Message text");
msgBox?.ShowNotification(NotificationIcon.Warning, "Title", "Message", "Detail text");

// Confirmation dialog — defaultChoice is the pre-selected button; return value is user's choice
ConfirmationResult result = msgBox.ShowConfirmation(
    ConfirmationIcon.General, "Title", "Proceed?",
    ConfirmationChoices.Yes | ConfirmationChoices.No, ConfirmationResult.Yes);
if (result == ConfirmationResult.No) return;

// ProgressProvider — progress bar with cancellation
var progress = tiaPortal.GetService<ProgressProvider>();
progress?.Update("Step description", "Detail text");
if (progress?.IsCancelRequested == true)
{
    // User requested cancellation — clean up and return
}

// FeedbackProvider — log to Inspector window (General Info tab)
var feedback = tiaPortal.GetService<FeedbackProvider>();
feedback?.Log(NotificationIcon.Information, "Operation completed successfully.");
feedback?.Log(NotificationIcon.Warning, "Skipped 3 items due to missing data.");

Important: In Add-In status callbacks (the OnUpdateStatus delegate passed to AddActionItem), GetService<T>() returns null. Only use services in action callbacks where COM access is fully available.

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Event handlers

Four events are available on TiaPortal. Always unsubscribe in a finally block.

Disposed

Fires when TIA Portal closes while the Openness client is still connected.

tiaPortal.Disposed += OnDisposed;
try
{
    // ... work ...
}
finally
{
    tiaPortal.Disposed -= OnDisposed;
}

private static void OnDisposed(object sender, EventArgs e)
{
    // TIA Portal was closed externally — clean up and exit
}

Notification

Fires for informational messages that require only an acknowledgment (OK).

tiaPortal.Notification += OnNotification;
try { /* ... */ }
finally { tiaPortal.Notification -= OnNotification; }

private static void OnNotification(object sender, NotificationEventArgs e)
{
    Console.WriteLine($"[TIA Notification] {e.Text}");
    // No response required — notification is auto-acknowledged
}

Confirmation

Fires for dialogs that require a decision. Must set e.Result to one of: "Yes", "YesToAll", or "No". Any other value throws an exception.

Auto-confirm pattern (most common in automation):

tiaPortal.Confirmation += OnConfirmation;
try { /* ... */ }
finally { tiaPortal.Confirmation -= OnConfirmation; }

private static void OnConfirmation(object sender, ConfirmationEventArgs e)
{
    e.Result = "Yes";
}

Authentication (V17+)

Fires when opening a UMAC-protected project. Use to specify the authentication method instead of passing credentials via UmacDelegate. Only fires for protected projects.

tiaPortal.Authentication += OnAuthentication;
try { /* open project ... */ }
finally { tiaPortal.Authentication -= OnAuthentication; }

private static void OnAuthentication(object sender, AuthenticationEventArgs e)
{
    // Choose one of: DesktopSso, Anonymous, Interactive, Credentials
    e.AuthenticationTypeProvider = AuthenticationTypeProvider.DesktopSso;
    // For Credentials mode, credentials are supplied separately via UmacDelegate
}

AuthenticationTypeProvider	Behaviour
DesktopSso	Signs in with the current Windows user — no password prompt
Anonymous	Uses the anonymous user account — no password prompt
Interactive	Shows TIA Portal login dialog to the user
Credentials	Reads credentials from the supplied UmacDelegate

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Exclusive access

Highly recommended for all non-trivial operations. Signals TIA Portal that a controlled activity is in progress and displays a dialog to the user.

using (ExclusiveAccess exclusiveAccess = tiaPortal.ExclusiveAccess("Generating project"))
{
    // All Openness operations here run under exclusive access

    // Optionally update the displayed message during long operations
    exclusiveAccess.Text = "Compiling software";
    // ...
    exclusiveAccess.Text = "Downloading to PLC";
}
// Exclusive access is released on dispose

Rules:

• Only one ExclusiveAccess can exist at a time — a second attempt throws a recoverable exception while the first is still active.
• Setting exclusiveAccess.Text = string.Empty or null clears the displayed message.

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Transactions

Group multiple modifications into a single undo unit. Requires an active ExclusiveAccess.

using (ExclusiveAccess exclusiveAccess = tiaPortal.ExclusiveAccess("Bulk edit"))
{
    using (Transaction transaction = exclusiveAccess.Transaction(project, "Create blocks"))
    {
        // Perform all modifications
        project.DeviceGroups.Create("Line_1");
        project.DeviceGroups.Create("Line_2");

        // MANDATORY: call CommitOnDispose() to persist changes
        // If this line is never reached, the transaction is rolled back
        transaction.CommitOnDispose();
    }
}

Rollback rules — critical:

• If CommitOnDispose() is never called → rolled back on dispose.
• If an exception occurs at any point before the transaction is disposed → rolled back, including when CommitOnDispose() was already requested or the exception was caught.
• After an EngineeringTargetInvocationException, a later CommitOnDispose() request can itself raise a recoverable exception; check CanCommit and do not assume persistence.

Not allowed inside a transaction: Compile, go online/offline, ProjectText import/export, opening or closing a global library, project create/open/open-with-upgrade/save/save-as/close, and changing a TIA Portal setting. These calls raise a recoverable exception while a transaction is active.

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Destructive-operation safety

These rules are mandatory for generated C# Openness code:

• Never bare .Delete(). Any destructive operation must be inside an active ExclusiveAccess scope and a Transaction when the API permits transactions.
• Use using blocks for ExclusiveAccess, Transaction, TiaPortal, and other disposable Openness objects so rollback and release behavior is explicit. Close projects explicitly according to lifecycle ownership; Project is not an IDisposable object.
• Call transaction.CommitOnDispose() only after every validation and mutation in the transaction has succeeded.
• Run or request a compile_check after generated block, tag, hardware, or HMI changes. Do not present generated project changes as deployable until that check passes.
• If an API refuses to run inside a transaction, state that limitation explicitly, use the narrowest possible ExclusiveAccess scope, and require a preview or user confirmation before the destructive call.

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Exception handling

Two top-level categories:

Category	Base type	Behaviour
Recoverable	Siemens.Engineering.EngineeringException	API call failed; session remains valid
Non-recoverable	Siemens.Engineering.NonRecoverableException	TIA Portal closed; restart required

Recoverable subtypes:

Type	Typical cause
EngineeringSecurityException	Missing access rights
EngineeringObjectDisposedException	Object no longer exists (e.g. deleted)
EngineeringNotSupportedException	Attribute or operation not available on this object
EngineeringTargetInvocationException	General failure despite a valid API call
EngineeringRuntimeException	Runtime error, e.g. invalid cast
EngineeringOutOfMemoryException	Insufficient resources in TIA Portal instance
EngineeringUserAbortException	Operation cancelled by the user (e.g. import dialog)
EngineeringDelegateInvocationException	Exception thrown inside a caller-supplied delegate
MissingProductsException	Project requires TIA Portal products/packages not installed (V18+)

Recommended catch order:

try
{
    // Openness work
}
catch (EngineeringSecurityException ex)
{
    Console.WriteLine($"Access denied: {ex.Message}");
}
catch (EngineeringObjectDisposedException ex)
{
    Console.WriteLine($"Object disposed: {ex.Message}");
}
catch (EngineeringNotSupportedException ex)
{
    Console.WriteLine($"Not supported: {ex.MessageData.Text}");
    foreach (ExceptionMessageData detail in ex.DetailMessageData)
        Console.WriteLine($"  Detail: {detail.Text}");
}
catch (MissingProductsException ex)
{
    Console.WriteLine($"Missing products: {ex.Message}");
}
catch (EngineeringTargetInvocationException)
{
    throw; // Do not swallow — rethrow for caller to handle
}
catch (EngineeringException)
{
    throw; // Do not swallow general engineering exceptions
}
catch (NonRecoverableException ex)
{
    Console.WriteLine($"Fatal — TIA Portal closed: {ex.Message}");
    // Must restart TIA Portal; the session is gone
}

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Project open mode

When opening multiple projects or working in multiuser environments:

// Primary — visible in project navigation, full read-write access
Project primary = tiaPortal.Projects.Open(
    new FileInfo(path), umacDelegate, ProjectOpenMode.Primary);

// Secondary — hidden from UI, always read-only regardless of user rights
Project secondary = tiaPortal.Projects.Open(
    new FileInfo(path), null, ProjectOpenMode.Secondary);

bool isPrimary = secondary.IsPrimary; // false

Rules:

• Only one primary project per TIA Portal instance.
• Secondary projects do not need a primary project to be open first.
• A user with write rights to a UMAC-protected project still gets read-only access when opening it as secondary.

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Object model contracts

Composition methods

Most engineering objects are accessed through compositions. Available methods:

Method	Behaviour
Create(id, ...)	Creates and adds a new instance. Signature varies per composition.
Find(id)	Finds by identifier. Non-recursive — searches current level only.
GetEnumerator()	Used implicitly in foreach loops.
Contains(obj)	Returns bool — checks if object is in the composition.
IndexOf(obj)	Returns int index of the object in the composition.
Import(path, ImportOptions)	Available on compositions that support import. ImportOptions: None or Overwrite.
Delete(obj)	Removes and deletes the instance.

Not all methods are available on every composition — check domain skills.

Object equality

// Reference equality (same .NET object reference)
bool sameRef = (objA == objB);

// TIA Portal identity equality (same engineering object, possibly different references)
bool sameObj = System.Object.Equals(objA, objB);

Use System.Object.Equals() when comparing objects retrieved through different navigation paths that may represent the same underlying engineering object.

DirectoryInfo / FileInfo — absolute paths only

All DirectoryInfo and FileInfo instances passed to Openness must use absolute paths. Relative paths cause an exception at runtime.

// Correct
var dir = new DirectoryInfo(@"C:\Projects\MyProject\Export");

// Wrong — will throw
var dir = new DirectoryInfo(@"Export");

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Bulk attribute access

Useful for dynamic tooling or when setting multiple attributes efficiently on HW objects.

Read all attributes

// Get names of all available attributes
IList<EngineeringAttributeInfo> infos =
    ((IEngineeringObject)deviceItem).GetAttributeInfos();

// Read all readable attributes in one call
IList<string> names = infos.Select(i => i.Name).ToList();
IList<object> values = ((IEngineeringObject)deviceItem).GetAttributes(names);

Filtered read by access mode