C# Null Conditional Operator inside method argument

Question

I have following methods:

float myMethod(MyObject[][] myList) 
{
      float a = 0;
      if (myListProcessingMethod(myList?.Where(x => x.mySatisfiedCondition()).ToList()))
      {
            a = 5;
      }
      return a;
}

bool myListProcessingMethod(List<MyObject[]> myList)
{
      bool isSuccess = false;
      if (myList.Any())
      {
            isSuccess = true;
      }
      return isSuccess;
}

I consider this condition:

if (myListProcessingMethod(myList?.Where(x => x.mySatisfiedCondition()).ToList()))

I refactor my condition to:

if (myList?.Length != 0)
{
      if (myListProcessingMethod(myList.Where(x => x.mySatisfiedCondition()).ToList()))
      {
            a = 5;
      }
}

Is this two conditions are equivalent? What is equivalent condition to first NullConditionOperator in traditional way? What is equivalent condition to second traditional checking using NullConditionalOperator?

Answer 1

The statement below can crash. If myList is null, myList?.Length will be null and myList?.Length != 0 will be true. That means myList.Where may crash with a null reference exception.

if (myList?.Length != 0)
{
  if (myListProcessingMethod(myList.Where(x => x.mySatisfiedCondition()).ToList()))
  {
        a = 5;
  }
}

you probably want

if (myList?.Length > 0) 
...

which will evaluate to true only if the list is not null and its Length is grater than 0.