> ## Documentation Index
> Fetch the complete documentation index at: https://help.dingtalk.io/llms.txt
> Use this file to discover all available pages before exploring further.

# ISNULL

> The ISNULL function checks whether a component is NULL. It works in multiple YiDA scenarios, such as Form and workflow design. The function takes one parameter, value1, and returns a boolean value.

The **ISNULL** function checks whether a component is NULL. It returns true if the value is NULL, and false otherwise.

## Supported Product Scenarios

The ISNULL function works in the following YiDA scenarios:

* Form (main table fields)
* Form (business association rules)
* Form (validation)
* Workflow design (validation rules)
* Workflow design (association actions)
* Integration and automation
* Workflow node
* Connector

## Format

```text theme={"theme":{"light":"github-light","dark":"github-dark"}}
ISNULL(value1)
```

## Attribute Description

| **Attribute** | **Required** | **Description**        |
| ------------- | ------------ | ---------------------- |
| value1        | Yes          | The value to evaluate. |

## Return Value

| **Return value type** | **Description**                                                                                                   |
| --------------------- | ----------------------------------------------------------------------------------------------------------------- |
| Boolean               | The evaluation result. Valid values:<br />• **true**: The value is not NULL.<br />• **false**: The value is NULL. |

## Usage Example

The following example uses the `ISNULL()` function to check whether an Attachment component is NULL.