Question mark and colon in statement. What does it mean?
C#asp.netWeb ServicesC# Problem Overview
What do the question mark (?
) and colon (:
) mean?
((OperationURL[1] == "GET") ? GetRequestSignature() : "")
It appears in the following statement:
string requestUri = _apiURL + "?e=" + OperationURL[0] + ((OperationURL[1] == "GET") ? GetRequestSignature() : "");
C# Solutions
Solution 1 - C#
This is the conditional operator expression.
(condition) ? [true path] : [false path];
For example
string value = someBooleanExpression ? "Alpha" : "Beta";
So if the boolean expression is true, value will hold "Alpha", otherwise, it holds "Beta".
For a common pitfall that people fall into, see this question in the C# tag wiki.
Solution 2 - C#
It is the ternary conditional operator.
If the condition in the parenthesis before the ?
is true, it returns the value to the left of the :
, otherwise the value to the right.
Solution 3 - C#
It's a ternary operator, or the short form for if..else
.
condition ? value if true : value if false
Solution 4 - C#
string requestUri = _apiURL + "?e=" + OperationURL[0] + ((OperationURL[1] == "GET") ? GetRequestSignature() : "");
can be translated to:
string requestUri="";
if ((OperationURL[1] == "GET")
{
requestUri = _apiURL + "?e=" + GetRequestSignature();
}
else
{
requestUri = _apiURL + "?e=";
}
Solution 5 - C#
This is also known as the "inline if", or as above the ternary operator. https://en.wikipedia.org/wiki/%3F:
It's used to reduce code, though it's not recommended to use a lot of these on a single line as it may make maintaining code quite difficult. Imagine:
a = b?c:(d?e:(f?g:h));
and you could go on a while.
It ends up basically the same as writing:
if(b)
a = c;
else if(d)
a = e;
else if(f)
a = g;
else
a = h;
In your case, "string requestUri = _apiURL + "?e=" + OperationURL[0] + ((OperationURL[1] == "GET") ? GetRequestSignature() : "");"
Can also be written as: (omitting the else, since it's an empty string)
string requestUri = _apiURL + "?e=" + OperationURL[0];
if((OperationURL[1] == "GET")
requestUri = requestUri + GetRequestSignature();
or like this:
string requestUri;
if((OperationURL[1] == "GET")
requestUri = _apiURL + "?e=" + OperationURL[0] + GetRequestSignature();
else
requestUri = _apiURL + "?e=" + OperationURL[0];
Depending on your preference / the code style your boss tells you to use.
Solution 6 - C#
In the particular case you've provided, it's a conditional assignment. The part before the question mark (?) is a boolean condition, and the parts either side of the colon (:) are the values to assign based on the result of the condition (left side of the colon is the value for true, right side is the value for false).
Solution 7 - C#
It means if "OperationURL[1]" evaluates to "GET" then return "GetRequestSignature()" else return "". I'm guessing "GetRequestSignature()" here returns a string. The syntax CONDITION ? A : B basically stands for an if-else where A is returned when CONDITION is true and B is returned when CONDITION is false.