Check String null or empty and replace with another string

Question

In here i want to, If AvailCode comes as a null or empty string then i need to show it "Temporary Unavailable".But my coding doen't show that one. (Consider only Avail Code).

var _staff = trv.GetBookDetails("4500").Select(b => new
{
    value = b.bookno,
    text =  b.bookname + " " + "/"+" " + b.AvailCode ?? "TemporaryUnavailable",  
});

Answer 1

the ?? operator only handles the NULL case, not the empty case

replace

b.AvailCode ?? "TemporaryUnavailable"

with

string.IsNullOrEmpty(b.AvailCode)? "TemporaryUnavailable" : b.AvailCode

so the correct line would be

text = b.bookname + " / " + (string.IsNullOrEmpty(b.AvailCode) ? "TemporaryUnavailable" : b.AvailCode),

Answer 2

?? operator which called null-coalescing operator returns the left-hand operand if the operand is not null; otherwise it returns the right hand operand.

This won't check for empty;

Use string.IsNullOrWhitespace method instead.

string.IsNullOrWhitespace(b.AvailCode) ? "TemporaryUnavailable" : b.AvailCode

Answer 3

Operator ?? has very low precedence, it's evaluated after the + operators on the left side. Therefore you can never really get null on the left side. You need to wrap into parenthesis:

  text =  b.bookname + " " + "/"+" " + (b.AvailCode ?? "TemporaryUnavailable"),  

or, in case you want to handle also empty:

  text =  b.bookname + " " + "/"+" " + (string.IsNullOrEmpty(b.AvailCode) ? "TemporaryUnavailable" : b.AvailCode),