---
title: "The DefinitionId method"
slug: "the-definitionid-method"
abstract: "Overview of the DefinitionId method and properties."
---
# The DefinitionId method

To define the definition ID for an event, use the `DefinitionId()` method.

| Property | Details |
| --- | --- |
| UT SDK method | `DefinitionId(string)` |
| Required/optional | Optional |
| Multiple invocations | Multiple invocations are forbidden and cause an *InvalidOperationException* exception |
| Value validation | Must contain a proper item ID value |