Question mark and colon in statement. What does it mean?

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() : "");


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Method 1

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.

Method 2

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.

Method 3

It’s a ternary operator, or the short form for if..else.

condition ? value if true : value if false

See Microsoft Docs | ?: operator (C# reference).

Method 4

string requestUri = _apiURL + "?e=" + OperationURL[0] + ((OperationURL[1] == "GET") ? GetRequestSignature() : "");

can be translated to:

string requestUri="";
if ((OperationURL[1] == "GET")
    requestUri = _apiURL + "?e=" + GetRequestSignature();
   requestUri = _apiURL + "?e=";

Method 5

This is also known as the “inline if”, or as above the ternary operator.

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.

a = b?c:(d?e:(f?g:h));

and you could go on a while.

It ends up basically the same as writing:

  a = c;
else if(d)
  a = e;
else if(f)
  a = g;
  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();
    requestUri = _apiURL + "?e=" + OperationURL[0];

Depending on your preference / the code style your boss tells you to use.

Method 6

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).

Method 7

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.

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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