What does question mark and dot operator mean in C 6 0

Question

With C  6 0 in the VS2015 preview we have a new operator      which can be used like this   public class A      string PropertyOfA   get  set            var a   new A    var foo    bar   if a  PropertyOfA    foo         somecode     What exactly does it do

User · Answer

This is relatively new to C  which makes it easy for us to call the functions with respect to the null or non-null values in method chaining  old way to achieve the same thing was  var functionCaller   this member  if  functionCaller   null      functionCaller someFunction var someParam    and now it has been made much easier with just  member  someFunction var someParam    I strongly recommend this doc page

User · Answer

It s the null conditional operator  It basically means    Evaluate the first operand  if that s null  stop  with a result of null  Otherwise  evaluate the second operand  as a member access of the first operand     In your example  the point is that if a is null  then a  PropertyOfA will evaluate to null rather than throwing an exception - it will then compare that null reference with foo  using string s    overload   find they re not equal and execution will go into the body of the if statement   In other words  it s like this   string bar    a    null   null   a PropertyOfA   if  bar    foo                    except that a is only evaluated once   Note that this can change the type of the expression  too  For example  consider FileInfo Length  That s a property of type long  but if you use it with the null conditional operator  you end up with an expression of type long    FileInfo fi           fi could be null long  length   fi  Length     If fi is null  length will be null

User · Answer

It can be very useful when flattening a hierarchy and or mapping objects   Instead of   if  Model Model2    null      Model Model2 Model3    null      Model Model2 Model3 Model4    null      Model Model2 Model3 Model4 Name    null      mapped Name    N A    else     mapped Name   Model Model2 Model3 Model4 Name      It can be written like  same logic as above   mapped Name   Model Model2  Model3  Model4  Name     N A     DotNetFiddle Net Working Example    the    or null-coalescing operator is different than the   or null conditional operator    It can also be used out side of assignment operators with Action   Instead of  Action lt TValue gt  myAction   null   if  myAction    null      myAction TValue       It can be simplified to   myAction  Invoke TValue     DotNetFiddle Example   using System   public class Program     public static void Main           Action lt string gt  consoleWrite   null       consoleWrite  Invoke  Test 1         consoleWrite    s    gt  Console WriteLine s        consoleWrite  Invoke  Test 2            Result      Test 2

[c#] What does question mark and dot operator ?. mean in C# 6.0?

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