/// <summary>Indexed properties create additional issues when the possibility of null is involved.</summary>
public string GetIndexedMember_OldWay(InterestingClass src)
{
if (src == null) return null;
if (src.Collection == null) return null;
if (src.Collection[0] == null) return null;
return src.Collection[0].FirstName;
}
/// <summary>NEW WAY: Null Conditionals operate on Indexed properties.</summary>
public string GetIndexedMember_NewWay(InterestingClass src)
{
// In this case, src is checked for null,
// Then Collection property is checked,
// Then the first member of the collection is checked
// Finally returning the desired property
return src?.Collection?[0]?.FirstName;
}
/// <summary>Linq function FirstOrDefault benefits from null conditional operator, as for reference types, first or default
/// return null if no member is found.</summary>
public string GetLinqMemberUsingNull()
{
InterestingClass ic = new InterestingClass();
ic.Collection = new List<InterestingMemberClass>();
// In the following line, an object is initialized using named arguments.
ic.Collection.Add(new InterestingMemberClass() { FirstName = "Jack", LastName = "Skellington" });
// In this line, the direct call to the constructor, using (), is omitted and the object is initialized.
// The call to the default constructor is automatically invoked.
ic.Collection.Add(new InterestingMemberClass { FirstName = "Sally", LastName = "Doll" });
return ic.Collection.FirstOrDefault(m => m.FirstName == "Jack")?.FirstName;
}
/// <summary>NEW WAY: Each member is checked for null, and short-circuits and returns null if the member to the left of the ?. operator is null.</summary>
public string GetName_NewWay(InterestingClass src)
{
return src?.Member?.LastName;
}
/// <summary>OLD WAY: Each member class needs to be checked for null before accessing additional members.</summary>
public string GetName_OldWay(InterestingClass src)
{
if (src == null) return null;
if (src.Member == null) return null;
if (src.Member.FirstName == null || src.Member.LastName == null) return null;
return src.Member.LastName;
}
