# MustBeNull

> An extension method for Assert.IsNull.

## Definition

* **Type:** Method
* **Namespace:** [UnityEngine.Assertions.Must](/engine/6000.7/script-reference/unityengine/assertions/must.md)
* **Assembly:** UnityEngine.CoreModule

## MustBeNull\<T>(T)

An extension method for [Assert.IsNull](/engine/6000.7/script-reference/unityengine/assertions/assert/isnull.md).

> **Warning:**
>
> **Deprecated.** Must extensions are deprecated. Use UnityEngine.Assertions.Assert instead

```csharp
[Conditional("UNITY_ASSERTIONS")]
public static void MustBeNull<T>(this T expected) where T : class
```

### Parameters

**** (T):&#x20;

### Examples

```csharp
using UnityEngine;
using UnityEngine.Assertions;
using UnityEngine.Assertions.Must;

public class AssertionExampleClass : MonoBehaviour
{
    MyClass myClassReference;
    void Update()
    {
        //Make sure the myClassReference reference is never set
        myClassReference.MustBeNull();
    }
}

public class MyClass {}
```

## MustBeNull\<T>(T, string)

An extension method for [Assert.IsNull](/engine/6000.7/script-reference/unityengine/assertions/assert/isnull.md).

> **Warning:**
>
> **Deprecated.** Must extensions are deprecated. Use UnityEngine.Assertions.Assert instead

```csharp
[Conditional("UNITY_ASSERTIONS")]
public static void MustBeNull<T>(this T expected, string message) where T : class
```

### Parameters

**** (T): **** (\[string]\(https\://learn.microsoft.com/dotnet/api/system.string)):&#x20;

### Examples

```csharp
using UnityEngine;
using UnityEngine.Assertions;
using UnityEngine.Assertions.Must;

public class AssertionExampleClass : MonoBehaviour
{
    MyClass myClassReference;
    void Update()
    {
        //Make sure the myClassReference reference is never set
        myClassReference.MustBeNull();
    }
}

public class MyClass {}
```