?? Operator in C# and its usage

This explains the C# Operator, ?? and its usage

C# Operator, ?? is called as null-coalescing operator. This is used to define a default value for both nullable value types and reference types.

EX:
int? i = null;
int j = (i ?? -1);

Here in the code, to assign a value of i, which is a nullable int type to j, which is int type, directly its not possible as both are different.
For this, to pass a default value when no value is present in i, ?? operator is used to specify the default value.
ie, when i is null, -1 is assigned to j