Background

In this post we will cover the Null-Conditional Operator ( ?. ).

 

Series

Here are other posts that covers .Net Operators:-

1. .Net:- Operator – The null-coalescing operator ??
   Date Published:- 2022-November-8th
   Link

 

Code

Code – HelloWorld

Code – HelloWorld

Outline

1. Get String Length
2. Print String and String Length

string FORMAT_WORLD_LENGTH = "{0}:- Length is {1}";
string strHelloWorld = "helloWorld";

Console.WriteLine
            (
                  FORMAT_WORLD_LENGTH
                , strHelloWorld
                , strHelloWorld.Length
            );

Output

Output – Text

helloWorld:- Length is 10

Code – HelloWorld

Code – Null

Code – Null

Outline

1. Get String Length
2. Print String and String Length
   • Fails as string is null

Code

string FORMAT_WORLD_LENGTH = "{0}:- Length is {1}";
string strNull = null;

Console.WriteLine
            (
                  FORMAT_WORLD_LENGTH
                , strNull
                , strNull.Length
            );

Output

Output – Text

Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
  at HelloWorld.Main () [0x00008] in <e877f77fc5404b3fa6220a9ba282a8d2>:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
  at HelloWorld.Main () [0x00008] in <e877f77fc5404b3fa6220a9ba282a8d2>:0 

Output – Image

Code – Null – Operator !=

Outline

1. Condition
   • Checks string to determine if it is null
   • The check is performed using the != operator
2. If string is not null
   • Get String Length
   • Print String and String Length

Code

string FORMAT_WORLD_LENGTH = "{0}:- Length is {1}";
string strNull = null;

if (strNull != 0)
{

     Console.WriteLine
            (
                  FORMAT_WORLD_LENGTH
                , strNull
                , strNull.Length
            );

}

Code – Null – Null Conditional Method ( Operator ?. )

Outline

1. Use ?.
   • strNull?.Length
     • The ?. means do not call the length method if the variable is null

Code

string FORMAT_WORLD_LENGTH = "{0}:- Length is {1}";
string strNull = null;

Console.WriteLine
            (
                  FORMAT_WORLD_LENGTH
                , strNull
                , strNull?.Length
            );

Output

Output – Text

:- Length is 

Output – Image

Code – Null – Null Conditional Method ( Operator ?. ) and null-coalescing operator ( ?? )

Outline

1. Use ?.
   • strNull?.Length
     • The ?. means do not call the length method if the variable is null
2. Use ??
   • ??
     • strNull?.Length ?? -1
       • If strNull is null, then display -1
     • strNull ?? ( “Variable ” + nameof(strNull) )
       • If strNull is null, display name of variable using (nameof(strNull))

Code

string FORMAT_WORLD_LENGTH = "{0}:- Length is {1}";
string strNull = null;

Console.WriteLine
            (
                  FORMAT_WORLD_LENGTH
                , strNull ?? ( "Variable " + nameof(strNull) )
                , strNull?.Length ?? -1
            ); 
        

Output

Output – Text

      
Variable strNull:- Length is 0
        

Output – Image

Summary

Please sanitize your variables.

At basic, see if they are nulls, empty, or zero.

Available Options includes:-

1. Nullability Checks
   • Explicit
     • Equality Operator ( == )
       • example
         • if variableA == null
     • Inequality Operator ( != )
       • example
         • if variableA != null
   • Implicit
     • Null Conditional Method ( ?. )
       • example
         • strNull?.Length
     • Null Conditional Method ( ?. ) and null-coalescing operator ( ?? )
       • example
         • strNull?.Length ?? –1

 

References

1. Microsoft
   • Learn > .NET > C# guide > Language reference > Operators and expressions
     • ?? and ??= operators (C# reference)
       Link
     • Equality Operator
       Link
     • Member access operators and expressions (C# reference)
       Link