more short code about if statement

Question

i wanted to try the following code:

//all arrays are List<T> type.
if (m.terms[0] != null && m.terms[0].labels != null && m.terms[0].labels[0].title == "Part-of-speech")
{
    result = true; 
}

but it occured runtime error occasionly in following situation

i. m.terms == null

ii. m.terms != null, but m.terms[0] does not intialized.

iii. m.terms != null, and m.terms[0] has been exist but m.terms[0].label does not initialized.

...

so i did modify it to like this:

if (m.terms[0] != null)
{
    if (m.terms[0].labels != null)
    {
        if (m.terms[0].labels[0].title == "Part-of-speech") { result = true; }
    }
}

is it the best way?

Answer 1

&& is a short circuiting operator, so the first way you wrote it and the second way will be functionally equivalent.

if (a && b && c)
{
    // work 
}

b will only be evaluated if a returns true. (Same goes for c).

In your code, checking m.terms[0].labels will not be a problem because you would have short-circuited out of the expression if m.terms[0] had been null.

To completely cover yourself, you'd want to possibly add checks for m and m.terms, however.

m != null && m.terms != null && m.terms.Count > 0 && m.terms[0] != null ...

As it evaluates from left to right, it will break on the first condition that doesn't pass and the rest will go unchecked.

Answer 2

int index = 0;
int labelIndex = 0;
string titleToCheck = "Part-of-speech";

if (m != null && m.terms != null && m.terms.Count > index)// or m.Length...
{
    if (m.terms[index] != null && m.terms[index].labels != null &&
        m.terms[index].labels.Count > labelIndex)
    {
        if (m.terms[index].labels[labelIndex].title == titleToCheck)
        {
            result = true; 
        }
    }
}

Answer 3

This is all about readability. C# uses Short-circuit evaluation so in functionality there is no difference.