Tag Access Code

Read and write tag values via scripts.

Reference → Code → Code Library → Tag Access

Reading and Writing Tags

The @Tag. prefix gives direct access to any tag in the Unified Namespace. Tag names use dot notation (@Tag.Folder.TagName). For tags whose name contains a /, see the Python note below.

Important: Digital tags accept the numeric values 0 and 1, never true / false. The tag's .State member is a read-only boolean convenience accessor — its setter is internal and cannot be written from user scripts.

C# Tag Access

// Reading tags
double temperature = @Tag.Process.Temperature;
bool motorRunning = @Tag.Motor1.Running.State;
string batchID = @Tag.Batch.ID;
DateTime timestamp = @Tag.System.CurrentTime;

// Writing tags
@Tag.Setpoint = 75.5;
@Tag.Pump.Start = 1;               // Digital tag: numeric 0 or 1, never true/false
@Tag.Pump.Stop = 0;
@Tag.Message = "Process started";  // Text tag: assign the value directly

// Array access
double[] values = @Tag.Data.Array;
@Tag.Data.Array[0] = 100;

// Quality and timestamp
TagQuality quality = @Tag.Process.Temperature.Quality;
DateTime lastUpdate = @Tag.Process.Temperature.Timestamp;

Python Tag Access

Python scripts have no @Tag. preprocessor. Tag names without a / in them can use the @Tag. dot-notation form; tag names with a / must be accessed as strings via TKGet / TKSet.

# Reading tags (simple dotted paths)
temperature = @Tag.Process.Temperature
motor_running = @Tag.Motor1.Running.State
batch_id = @Tag.Batch.ID

# Writing tags
@Tag.Setpoint = 75.5
@Tag.Pump.Start = 1                 # Digital tag: always numeric 0 or 1
@Tag.Message = "Process started"    # Text tag: assign the value directly

# Tags whose UNS path contains a '/' must be accessed as strings.
# Example: a tag at path "Plant/Line1/Temperature"
temp = TKGet("Tag.Plant/Line1/Temperature")
TKSet("Tag.Plant/Line1/Temperature", 75.5)

# NumPy on array-typed tags
import numpy as np
values = np.array(@Tag.Data.Array)
mean_value = np.mean(values)
@Tag.Statistics.Mean = mean_value

Tag Properties and Methods

// Tag properties
public class TagProperties
{
    // Basic properties
    string Name { get; }
    object Value { get; set; }
    TagQuality Quality { get; }
    DateTime Timestamp { get; }

    // Extended properties
    double Min { get; set; }
    double Max { get; set; }
    string Units { get; }
    string Description { get; }

    // Methods
    void ForceValue(object value);
    void Subscribe(Action<TagChangeEvent> handler);
    void Unsubscribe();
    bool WriteWithConfirm(object value, int timeout);
}

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