Pass string if the parameter value is null

Question

I need to pass multiple parameters in a function. My requirement is the parameter value should not be NULL. If the parameter is NULL pass "TBD" instead.

eg

getBookInfo (string bookId, string bookName, string bookAuthor) 
//if any of the parameters is NULL, pass "TBD" string in parameter

How can I do this? Can I do this using ternary operator, and if so, how?

Answer 1

Try doing it this way when calling your method:

getBookInfo (bookId ?? "TBD", bookName ?? "TBD", bookAuthor ?? "TBD");

The ternary operator ?: is a waste when you can use the null coalescing operator ?? .

Answer 2

Just put an if condition inside this function and check for null values of these three variables and if found null , you can assign the default values immediately after the if check and then continue further execution.

Something like this :

getBookInfo (string bookId, string bookName, string bookAuthor)
{
   bookId = (bookId == "" ) ? bookId : "TBD";
   // other variables same way.
}

Hope this clears it.

Answer 3

Using ternary it would be like:

getBookInfo (bookId == null ? "TBD" : bookId, bookName == null ? "TBD" : bookName, bookAuthor == null ? "TBD" : bookAuthor)

but I think that is not very clear to read...

Answer 4

private void GetBookInfo(string bookId, string bookName, string bookAuthor)
        {
            // if any of the parameter is NULL, set "TBD" as the value
            bookId = bookId == null ? "TBD" : bookId;
            bookName = bookName == null ? "TBD" : bookName;
            bookAuthor = bookAuthor == null ? "TBD" : bookAuthor;

            // rest of the code goes here
        }

Answer 5

Before passing parameter check whether parameter is null or not. For example

string bookid;
string bookName;
string bookAuthor;
if(bookid==null)
bookid="TBD";
if(bookName==null)
bookName="TBD";
if(bookAuthor==null)
bookAuthor="TBD";
getBookInfo (string bookId, string bookName, string bookAuthor)

This will set value "TBD" if value of any field would be null. Hope it resolved your issue. Thanks

Answer 6

You could also provide an overload of the method which would allow the developer to provide a limited number of parameters. The overload would call the method with additional parameters passing default values for parameters it doesn't already have.

public void GetBookInfo (string bookID)
{
    // Call overload passing bookID and empty string as book name
    return GetBookInfo(bookId, string.Empty);
}

public void GetBookInfo (string bookID, string bookName)
{
    // Call overload passing bookID, bookName and empty string as author
    return GetBookInfo(bookId, bookName, string.Empty);
}

public void GetBookInfo (string bookID, string bookName, string author)
{
    // All 3 parameters are populated here, get the book info...
}

Answer 7

With the newer versions of C# you can do this (add default values to arguments):

public void getBookInfo (string bookId = "TBD", string bookName = "TBD", string bookAuthor = "TBD") 

This also makes the arguments optional.