# addEventHandler

- Module: [Aspire.Hosting.Azure.WebPubSub](/reference/api/typescript/aspire.hosting.azure.webpubsub.md)
- Version: `13.4.0`
- Kind: `method`
- Source: [GitHub](https://github.com/microsoft/aspire)

Adds an event handler to an Azure Web PubSub hub.

## Definition

```typescript
interface AzureWebPubSubHubResource {
  // ... omitted for brevity
  addEventHandler(
    urlExpression: ReferenceExpression,
    userEventPattern?: string,
    systemEvents?: string[]): AzureWebPubSubHubResource
}
```

## Parameters

- `urlExpression` (`ReferenceExpression`)
- `userEventPattern` (`string`) `optional` `= *`
- `systemEvents` (`string[]`) `optional`

## Returns

[AzureWebPubSubHubResource](/reference/api/typescript/aspire.hosting.azure.webpubsub/azurewebpubsubhubresource.md) `builder`

## Applies to

- [AzureWebPubSubHubResource](/reference/api/typescript/aspire.hosting.azure.webpubsub/azurewebpubsubhubresource.md)