How to determine whether object reference is null?

Question

What is the best way to determine whether an object reference variable is null?

Is it the following?

MyObject myObjVar = null;
if (myObjVar == null)
{
    // do stuff
}

Kino

If you want to default to something, you can always do MyObject obj = myObjVar ?? DefaultObjVar – Jaquesdalcroze

Answer 1

Yes, you are right, the following snippet is the way to go if you want to execute arbitrary code:

MyObject myObjVar; 
if (myObjVar == null) 
{ 
    // do stuff 
} 

BTW: Your code wouldn't compile the way it is now, because myObjVar is accessed before it is being initialized.

Sumba

Answer 2

You can use Object.ReferenceEquals

if (Object.ReferenceEquals(null, myObjVar)) 
{
   ....... 
} 

This would return true, if the myObjVar is null.

Reimpression

This is useful if you want to override the == operator for an object. – Eau

If you happen to be wanting to test for null inside your implementation of == then I think Object.ReferenceEquals is essential. – Boutonniere

Answer 3

The way you are doing is the best way

if (myObjVar == null)
{
    // do stuff
}

but you can use null-coalescing operator ?? to check, as well as assign something

var obj  = myObjVar ?? new MyObject();

Chiccory

I think that the null-coalescing operator was introduced in C# 2 – Fisch

Answer 4

you can:

MyObject myObjVar = MethodThatMayOrMayNotReturnNull();
if (if (Object.ReferenceEquals(null, myObjVar)) 
{
    // do stuff
}

Lute

why the need for two if statements? – Reversible

Answer 5

In C# 7.0 you can use is null:

MyObject myObjVar = null;
if (myObjVar is null)
{
    // do stuff
}

Stratiform