Expression Reference Information

This section includes reference information about the Sequence Expression language.

Expressions and .NET Types

Sequence expressions support the following types.

Nullable Types

Nullable types represent value-type variables that you can assign a null value.

Numeric Types

Integral Types

  • SByte
  • Byte
  • Int16
  • Int32
  • Int64
  • UInt16
  • UInt32
  • UInt 64

Real Types

  • Single
  • Double
  • Decimal

Enums and Arrays

Enum Types

In the expression language, access to the enum member is defined as a string that represents a member of that enum type.

act.Status = "Completed"

Array Type

The expression language supports creating and initializing an array instance.

new DateTime[] { DateTime.Now }

Accessible Types

Accessible types are types that you can reference in expressions.

Access Rules

  • The type is primitive.
  • The type member is public.
  • The type is exclusively added to the collection of the well-known types of the expression parse context.
  • The type is member of the built-in predefined types.

Constants

  • The predefined constants true and false define the two values of the boolean type.
  • The predefined constant null defines a null reference.
  • The null constant is of Object type, but is also implicitly convertible to any reference type.

Expression Parsing

Expression parsing is a process that converts a string that represents an expression into an expression tree.

Expression Normalization

Expression normalization is an ability to modify an expression tree during the parsing process.

Default Member Lookup

Uses DefaultMemberAttribute to locate a type member when it is not found on the type itself.

Custom Member Lookup

Uses CustomMemberProviderAttribute to locate a type member when it is not found on the type itself.

The underlined compiled expression is a delegate generated by the .NET LambdaExpression.Compile method.

Activities and Activity Views

Variable Name
Description
  • Start
  • End
  • IfElse
  • Empty
ActivityView
  • Message
  • Split Or
  • Join And
  • Switch
  • Store Procedure
  • Database Listener
  • Assign

DataBoundActivityView
  • FormActivity
FormActivityView
  • TaskActivity
TaskActivityView
  • External Service Consumer
  • WCF Consumer
  • Web Service Consumer
  • Web Service Listener

DynamicMethodActivityView
  • Error Handler

ErrorHandlerActivityView
  • Sub Workflow

SubWorkflowActivityView
SharePoint Listener
SharePointActivityView