Code inspection: Expected a type derived from 'Component' or 'MonoBehaviour'

The Unity.ExpectedComponent inspection ensures type safety when using string-based Unity APIs, such as GameObject.AddComponent(string) and GameObject.GetComponent(string). It flags cases where a specified type exists but does not inherit from the required base class (UnityEngine.Component for built-in types or UnityEngine.MonoBehaviour for user-defined types).

How it works

The inspection uses Unity-specific reference providers to resolve the string literal to a type in the project or libraries. Once the type is resolved, the analyzer checks if it satisfies the inheritance requirements of the method being called.

Validation rules:

For built-in types (from Unity assemblies): The type must derive from UnityEngine.Component.
For user-defined types (in the current project): The type must derive from UnityEngine.MonoBehaviour.

This prevents runtime errors or silent failures where Unity would be unable to add or find the specified component because it doesn't match the expected signature.

Example

In this example, MyPlainClass does not inherit from MonoBehaviour, so it cannot be added as a component to a GameObject.

                public class MyPlainClass { }

                public class MyScript : MonoBehaviour
                {
                    void Start()
                    {
                        // Reported: MyPlainClass is not a MonoBehaviour
                        gameObject.AddComponent("MyPlainClass");
                    }
                }
            

                public class MyComponent : MonoBehaviour { }

                public class MyScript : MonoBehaviour
                {
                    void Start()
                    {
                        // After fix: MyComponent is a MonoBehaviour
                        gameObject.AddComponent("MyComponent");
                    }
                }
            

26 March 2026