what does null colelesing do in C# code example

Example 1: null coalescing operator c#

//the null coalescing operator for c# is ??
int? x = null;
int y = 9;
return x ?? y; 
//Will return the value of x if x is not null else return y

Example 2: c# null accessor

int? length = people?.Length; // null if people is null