Assign and check for a null value at the same time?

c# ternary operator null check
null coalescing operator
c# if not null
c# elvis operator
c# if null return
.net coalesce
double ternary operator c#
c# coalescing assignment

I have the following scenario:

if(xml.Descendants(ns + "Children").FirstOrDefault() != null)
{
    XElement children = xml.Descendants(ns + "Children").FirstOrDefault();
}

Is there a way I can check for null and assign the value at the same time instead of having to search for the value twice, something similar to:

//Not sure if this is correct.
if (XElement children = xml.Descendants(ns + "Children").FirstOrDefault() != null)
{

}

A variable assignment also returns the value. So the syntax in the form of the following will do:

SomeType someVariable;
if ((someVariable = valueToAssign) != null)
{
    // valueToAssign was not null
}

In your case:

XElement children;

if ((children = xml.Descendants(ns + "Children").FirstOrDefault()) != null)
{

}

Using the New Null Conditional Operator in C# 6 |, In every one of those null checks, the null conditional operator may help you to write The ?[] syntax has the same semantics as the ?. operator: It's how you access the If people is null, thisName is assigned the value null. The Null Coalescing Operator is the binary operator that can have either True of False two values. It is used to check the null values. In case if you want to assign a default value to any variable the time when it is null, then you can use Null Coalescing Operator(??). The example is given below to explain the operator,

I would do it this way:

XElement children = xml.Descendants(ns + "Children").FirstOrDefault();
if(children != null)
{
    //use children
}

?? and ??= operators, The null-coalescing operator ?? returns the value of its left-hand operand if later, the null-coalescing assignment operator ??= assigns the value of its of the ?? operator to make the argument-checking code more concise:. null is often defined to be 0 in those languages, but null in Python is different. Python uses the keyword None to define null objects and variables. While None does serve some of the same purposes as null in other languages, it’s another beast entirely. As the null in Python, None is not defined to be 0 or any other value.

You could just do

XElement children = xml.Descendants(ns + "Children").FirstOrDefault();

and then check for null

if (children != null) {...}

TypeScript 2.0 � TypeScript, In strict null checking mode, the null and undefined values are not in the a compile-time error if the object or function is of a type that includes null or undefined . have initializers and may be assigned to in constructors within the same class� This time Mike is wrong. There is a place for null, including Nullable<bool> and Nullable<int>. Null means no value. null is a special value that means no value. For plain C pointers it’s just a name for the magic number 0 (I know that according to the specification it can have another numerical representation than 0, but in reality it doesn

You can assign and then test the assigned value in a single statement (but not declare it):

XElement children = null;

if ((children = xml.Descendants(ns + "Children").FirstOrDefault()) != null)
{    
}

But this is functionally the same as assigning and testing afterwards:

var children = xml.Descendants(ns + "Children").FirstOrDefault();

if (children != null)
{      
}

I would favour the latter because I think it is more readable (also lets you use var).

Assignment of a null value to a variable will never itself generate an error (assuming this is just a standard local variable), subsequent use of that variable might do. So either solution above will be safe assuming xml itself isn't null.

PL/SQL Collections and Records, Data Type Compatibility � Assigning Null Values to Varray or Nested Table Variables A composite data type stores values that have internal components. Because you must store or retrieve all elements at the same time, a varray might To determine when team is empty, print_team uses the collection method COUNT� The PowerShell $null often appears to be simple but it has a lot of nuances. Let’s take a close look at $null so you know what happens when you unexpectedly run

You can do this though:

null != children = xml.Descendants(ns + "Children").FirstOrDefault()

empty - Manual, Determine whether a variable is considered to be empty. A variable is Returns FALSE if var exists and has a non-empty, non-zero value. Otherwise Arguably another bug. empty() behaves in the same way. So things echo "Time taken: " . Always evaluates the default value (as oposed to cond ? nonNull() : notEvaluated()) This could be circumvented by passing a Callable instead of a default value, but making it somewhat more complicated and less dynamic (e.g. if performance is an issue). By the way, you encounter the same disadvantage when using Optional.orElse();-)

The Null Variable, To discard the return value from a function, assign it to !NULL. For example, suppose you NULL eliminates the need to test whether array is defined in each iteration of the WHILE loop. The same error occurs when trying to convert a ! Data Type and Structure of Expressions � Date/Time Data � The Null Variable � Type� A null value is an acceptable value. However, too many null values often point to an unnormalized table. For instance, if you store customer phone and fax numbers, you might end up with a lot of

Nullable Types in C#, C# 2.0 introduced nullable types that allow you to assign null to value type For example, int i = null will give you a compile time error. A nullable of type int is the same as an ordinary int plus a flag that says whether the int has a value or Use HasValue property to check whether value is assigned to nullable type or not . Do not catch NullPointerException.That is a bad practice. It is better to ensure that the value is not null. Method #4 will work for you. It will not evaluate the second condition, because Java has short-circuiting (i.e., subsequent conditions will not be evaluated if they do not change the end-result of the boolean expression).

C#'s null-coalescing operator (??) explained � Kodify, Let's look at an operator that handles possible null values with a little bit of code. We do that in one of two ways: make a new object as the default value or use a A typical way to use the null-coalescing operator is to assign a value to a But that time gain is easily lost when this operator makes the code� If at all u need to assign a NULL value, there are two ways. 1. A=3D NULL, in which case, the values will be rejected if ur DML for = A cannot accommodate a NULL value. 2. If u don't assign any thing, then it automatically takes a NULL = value. Apart from these, I don't see any other way for to assign NULL values. Hope this answers ur questions.

Comments
  • Ah i had no idea, so my syntax was correct, I just guessed lol
  • @Xaisoft Your syntax wasn't correct, you were also declaring it in-line, which isn't valid.
  • I like this approach, I didn't notice the double brace at first. Thanks.
  • This is what I was doing, but if no Children were found, I would get an error.
  • @Xaisoft makes no sense, because if that is the case, your code would also throw an error
  • No worries! You might also want to check out the null-coalescing operator: msdn.microsoft.com/en-us/library/ms173224.aspx
  • If no Children elements are found, this throws a null exception.
  • @Xaisoft: mhh, that should not be the case. It would be the case if you use First but FirstOrDefault should return null
  • When FirstOrDefault says it returns a default value, is that a default value you specify or is it the default value for the specified type, for example, reference variables would get null?
  • @Xaisoft: default value for the specified type, null in this case.
  • @Xaisoft Likely default(T), which for all reference types is null.
  • Yes it returns null if no children are found, but that is what I want to avoid having to check for null and then assign the value.
  • @Xaisoft It is functionally the same as assigning it and then checking the variable afterwards - just it does it in one line. It isn't doing any less work.
  • Nice. I'm going blind, I din't notice the double brace at first, but this works great.