C# expressions

When working with Elsa, you'll often need to write dynamic expressions. This page provides a glossary of C# expressions that you can use.

Elsa uses Roslyn to implement the C# expression evaluator..

Common

Out of the box, all types are registered from the System and System.Linq namespace.

Activity output

The following functions are specific to handling activity output.

Workflow variables and input

The following functions are specific to handling workflow variables and input.

Workflow variables

There are two ways to get variables from the workflow:

• Variables.Get("MyVariable")
• Variables.MyVariable

The first method is useful when you want to get a variable whose name is not known at build-time. The second method is useful when you know the name of the variable at build-time, which has the added benefit of providing intellisense.

Similarly, there are two ways to set variables in the workflow:

• Variables.Set('MyVariable', "myValue");
• Variables.MyVariable = "myValue";

Workflow input

To get the input of the workflow, use the Input.Get(string) function.

For example, if you run a workflow providing the following input:

{
  "input": {
    "name": "Alice"
  }
}

You can get the name field using the following expression:

Input.Get("name")

Workflow

These functions and properties are specific to working with workflows.