# UiPath.Studio.Activities.Api.Expressions

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

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. |