Question

How do I sort a list on a nullable int property using System.Collections.Generic.List<T>.Sort?

Or do I have to do a manual sort because that’s not possible?

Answer 1

First you need to decide how a null value compares with items with a value. Then you can perform the comparison. For example if you decide that null is always “less than” a non-null:

list.Sort((x,y) => {
  if(!x.Nullable.HasValue) {
     if(!y.Nullable.HasValue) return 0; // equal
     else return -1; // y is greater
  }
  else
  {
    if(!y.Nullable.HasValue) return 1; // x is greater
    if(x == y) return 0; // equal
    if(x < y) return -1; // y is greater
    else return 1;
  }
}