Best way to check for nullable bool in a condition expression if

Question

I was wondering what was the most clean and understandable syntax for doing condition checks on nullable bools    Is the following good or bad coding style  Is there a way to express the condition better more cleanly   bool  nullableBool   true  if  nullableBool    false          else           especially the if  nullableBool    false  part   I don t like the if  x HasValue  amp  amp  x Value  style       not sure whether the question has been asked before     couldn t find something similar with the search

User · Answer

Lets check how the comparison with null is defined:

static void Main()
    {
        Console.WriteLine($"null != null  => {null != null}");
        Console.WriteLine($"null == null  => {null == null}");
        Console.WriteLine($"null != true  => {null != true}");
        Console.WriteLine($"null == true  => {null == true}");
        Console.WriteLine($"null != false => {null != false}");
        Console.WriteLine($"null == false => {null == false}");
    }

and the results are:

null != null  => False                                                                                                                                                                                                                                  
null == null  => True                                                                                                                                                                                                                                   
null != true  => True                                                                                                                                                                                                                                   
null == true  => False                                                                                                                                                                                                                                  
null != false => True                                                                                                                                                                                                                                   
null == false => False

So you can safely use:

// check if null or false
if (nullable != true) ...

// check if null or true
if (nullable != false) ...

// check if true or false
if (nullable != null) ...

User · Answer

I think its up to you  I certainly think the  HasValue approach is more readable  especially with developers not familiar with the    syntax   The other point of a nullable boolean type is that it is tristate  so you may want to do something else when it is just null  and not default to false

User · Answer

Actually I think that  nullableBool    false  is a legitimate option especially when you are trying to evaluate a nullable bool in linq  For example  array Select v   gt  v nullableBool    false   from v in array where v nullableBool    false   Is cleaner in my opinion as opposed to  array Select v   gt  v nullableBool HasValue   v nullableBool Value   false   from v in array where v nullableBool HasValue   v nullableBool Value   false

User · Answer

If you re in a situation where you don t have control over whether part of the condition is checking a nullable value  you can always try the following   if  someInt    6  amp  amp  someNullableBool    null   false    bool someNullableBool         perform your actions if true     I know it s not exactly a purist approach putting a ternary in an if statement but it does resolve the issue cleanly   This is  of course  a manual way of saying GetValueOrDefault false

User · Answer

Given enum  public enum PublishMode   Edit  View     you can do it like here   void MyMethod PublishMode  mode               var publishMode   mode    PublishMode Edit     or        if  mode   PublishMode Edit    someValue

User · Answer

Use extensions   public static class NullableMixin       public static bool IsTrue this System Nullable lt bool gt  val            return val    true            public static bool IsFalse this System Nullable lt bool gt  val            return val    false            public static bool IsNull this System Nullable lt bool gt  val            return val    null            public static bool IsNotNull this System Nullable lt bool gt  val            return val HasValue            Nullable lt bool gt  value   null  if value IsTrue         do something with it

User · Answer

Just think of bool  as having 3 values  then things get easier   if  someNullableBool    true         only if true if  someNullableBool    false        only if false if  someNullableBool    null         only if null

User · Answer

If you only want to test for true against null false  One I ve just used and reads quite well is  bool  someCondition   null if  someCondition Equals true

User · Answer

I think a lot of people concentrate on the fact that this value is nullable  and don t think about what they actually want     bool  nullableBool   true  if  nullableBool    true             true else            false or null   Or if you want more options     bool  nullableBool   true  if  nullableBool    true             true else if  nullableBool    false             false else            null    nullableBool    true  will never return true if the bool  is null  P

User · Answer

How about using GetValueOrDefault  which is pretty self-explaining and allows to use whatever default you want   if  nullableBool GetValueOrDefault false

User · Answer

You may not like it  but personally I find  if  x HasValue  amp  amp  x Value    the most readable  It makes it clear you are working with a nullable type and it makes it clear you are first checking whether the nullable type has a value before acting on it conditionally   If you take your version and replace the variable with x also it reads   if  x    false    Is that as clear  Is it obvious x is a nullable type  I ll let you decide

User · Answer

If you want to treat a null as false  then I would say that the most succinct way to do that is to use the null coalesce operator       as you describe   if  nullableBool    false

User · Answer

Another way is to use constant pattern matching  if  nullableBool is true     if  nullableBool is false     if  nullableBool is null      Unlike the operator     when reading the code  this will distinguish the nullable type check from ordinary  quot code with a smell quot

[c#] Best way to check for nullable bool in a condition expression (if ...)

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