# UiPath.Studio.Activities.Api.Expressions

> UiPath.Studio.Activities.Api.Expressions namespace for building Studio activities, including the service for expanding dynamic expressions at design time introduced in v21.10.

In this section you can find more information on how to build activities using **UiPath.Studio.Activities.Api.Expressions**.

## IDesignTimeExpressionExpanderService
:::note
This feature was introduced in UiPath.Studio.Activities.Api v21.10.
:::

Service used to expand/unwrap dynamic expressions at design time, e,g, dynamic file paths.

### Properties

| Type | Name | Description |
| --- | --- | --- |
| string | ExpandString | Expands the given string expression. |
| string | GenerateDynamicString | Generates a dynamic expression string based on the specified value. For example, if the given string is a file path that is user-specific (e.g. a file path that points to something in My Documents), this will turn that static string into a dynamic, user-agnostic expression that can be "expanded" by `ExpandString(string)` at design time and evaluated by WWF at runtime. It turns *C:UsersUserSomeFolder* to something like `string.Format("{}\SomeFolder", Environment.UserFolder)`. |

## IExpressionService
:::note
This feature was introduced in UiPath.Studio.Activities.Api v21.4.
:::

Interface for returning tokens from an expression.

### Methods

#### IEnumerable<Token> GetIdentifierAndLiteralList(string expression, string expressionLanguage)

Returns a flat list of all identifiers and literals encountered in the given expression, in the order in which they were encountered.

| Parameter Type | Parameter Name | Remarks |
| --- | --- | --- |
| string | expression | The expression to tokenize. |
| string | expressionLanguage | The dark theme. |

## Token
:::note
This feature was introduced in UiPath.Studio.Activities.Api v21.4.
:::

The smallest element of an expression, for example an identifier or a literal value.

### Properties

| Type | Name | Description |
| --- | --- | --- |
| string | StringRepresentation | The name of the token. |
| string | TokenType | The [token type](https://docs.uipath.com/sdk/other/latest/developer-guide/uipathstudioactivitiesapiexpressions#tokentype). |
| Type | ExpressionType | The type of expression. |

## TokenType
:::note
This feature was introduced in UiPath.Studio.Activities.Api v21.4.
:::

The type of token.

### Constants

| Type | Name | Description |
| --- | --- | --- |
| string | ObjectCreation | The token represents the creation of an object. |
| string | IdentifierReference | The token represents the referencing of an object or method by name. |
| string | LiteralUsage | The token represents the usage of a literal value. |