Script

The Script activity executes a C# expression using DynamicExpresso, a sandboxed interpreter. It is the primary way to compute values, read or write workflow context variables, and perform data transformations that standard activities do not cover.

Purpose

Use the Script activity to:

• Read and write workflow context variables
• Perform calculations or data transformations
• Execute custom logic that doesn't require conditional branching
• Derive intermediate values for use in subsequent activities

Configuration

Code Expression

Write a single C# expression. The expression is evaluated at runtime inside a sandboxed interpreter. It does not have access to the full .NET runtime — only the types and variables listed below.

Single Exit Path

Script has only one outcome path. Execution always continues to the next connected activity unless the script throws an unhandled exception (see Error Behaviour).

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The Context Dictionary

At runtime the script receives a variable called Context, which is the workflow's shared state dictionary (OrderedDictionary). All workflow variables live here.

Syntax	Effect
Context["key"]	Read a value
Context["key"] = value	Write or update a value

Context and context (lowercase) are both valid — they refer to the same object.

Pre-populated Keys

The following keys are available in every workflow run without any setup:

Key	Type	Description
RunName	string	Name of the current workflow run
StartedBy	string	Username of the person who started the run
StartedBy_FullName	string	Full display name of the person who started the run
Tenant	string	Current tenant identifier
StartTime	string	UTC start time of the run
NoOfExecutedActivities	int	Count of activities executed so far

Any parameters passed when launching the workflow and any global variables configured in the system are also injected before execution begins.

Variable Interpolation Syntax

In addition to Context["key"], the script field supports {VariableName} shorthand. Before the script is evaluated, every {VariableName} token is replaced with the current context value. This makes expressions shorter but is purely a substitution — it does not bypass the context dictionary.

// These two lines are equivalent:
Context["Total"] = (double)Context["Qty"] * (double)Context["Price"]
Context["Total"] = {Qty} * {Price}

Use Context["key"] = value for writes; {key} is convenient for reads in short expressions.

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Available Types and Methods

The script runs inside a sandboxed interpreter. Only the following types are available:

Type	Notes
string	All instance methods, string.Format, etc.
int, long, double, bool	Primitive numeric and boolean types
DateTime	DateTime.Now, DateTime.UtcNow, .Year, .Month, .AddDays(n), etc.
Convert	Convert.ToInt32(), Convert.ToDouble(), Convert.ToString(), etc.
Enumerable	LINQ extension methods: .Where(), .Select(), .Sum(), .First(), etc.
JObject	Newtonsoft JSON object — useful for parsing JSON string values

Lambda expressions are supported, so LINQ chains work:

Context["Total"] = Enumerable.Range(1, 5).Sum(x => x)

Types not available include Math, Regex, List<T>, Dictionary<K,V>, file/IO types, and all custom application types. If you need those, consider wrapping logic in a stored procedure or a custom activity.

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Error Behaviour

If the script throws any exception at runtime, the activity:

1. Logs the exception message to the workflow run log
2. Returns an Error status, stopping the workflow

Always test scripts with realistic context values. A common mistake is reading a key that has not been set yet — this returns null and causes a null-reference or cast error downstream.

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Examples

Read and write a context value

Context["Year"] = DateTime.Now.Year

Derive a value from two existing context variables

Context["Total"] = (double)Context["Qty"] * (double)Context["Price"]

Using interpolation shorthand:

Context["Total"] = {Qty} * {Price}

Copy and rename a context key

Context["Year"] = Context["FinancialYearParameter"]

String concatenation

Context["FullName"] = (string)Context["FirstName"] + " " + (string)Context["LastName"]

Date extraction

Context["CurrentYear"] = DateTime.Now.Year
Context["CurrentMonth"] = DateTime.Now.Month

Parse a JSON context value

Context["City"] = JObject.Parse((string)Context["AddressJson"])["city"].ToString()

LINQ over a range

Context["SumOf10"] = Enumerable.Range(1, 10).Sum(x => x)

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Usage Notes

• Not for regular users — requires C# knowledge and familiarity with the context dictionary pattern.
• Sandboxed — only the types listed above are available. This is intentional; the interpreter does not execute arbitrary .NET code.
• Single expression — the script is evaluated as a single expression. Multi-statement blocks (e.g. if/else, for loops) are not supported. Use chained ternary operators or LINQ for conditional logic.
• Type casting — context values are stored as object. Cast explicitly when passing to typed operations: (double)Context["Amount"].
• Case-sensitive keys — Context["Year"] and Context["year"] are different entries.

JSON Reference

{
  "discriminator": "ScriptWorkflowActivity",
  "activityId": "<uuid>",
  "name": "Script",
  "positionX": 0,
  "positionY": 0,
  "advanceRule": 2,
  "script": "Context[\"Year\"] = DateTime.Now.Year"
}

Property	Type	Description
script	string	Corresponds to the Code Expression field. A C# expression evaluated by the DynamicExpresso interpreter. Has access to Context (the workflow context dictionary), DateTime, Convert, Enumerable, JObject, and primitive types. Supports {variable} interpolation before evaluation.