New operator ?? in c#

The operator '??' is in c#, which is used check the value is null.
Previously, we used to check the null value by the following methods..

if (a!=null) { c=a; } or
c = ((a!=null)?a:0);

we can do the same checking with the new operator ?? like this..
c = a??0;

By this statement the value a will be assigned to c if it is not null else the zero will be assigned.