Nullable types better way to check for null or zero in c

Question

I m working on a project where i find i m checking for the following in many  many places   if item Rate    0    item Rate    null        more as a curiousity than anything  what s the best way to check for both cases   I ve added a helper method which is   public static bool nz object obj        var parsedInt   0      var parsed   int TryParse obj ToString    out parsedInt       return IsNull obj      parsed  amp  amp  parsedInt    0       Is there a better way

User · Answer

You code sample will fail  If obj is null then the obj ToString   will result in a null reference exception  I d short cut the process and check for a null obj at the start of your helper function  As to your actual question  what s the type you re checking for null or zero  On String there s a great IsNullOrEmpty function  seems to me this would be a great use of extension methods to implement an IsNullOrZero method on the int  type   Edit  Remember  the     is just compiler sugar for the INullable type  so you could probably take an INullable as the parm and then jsut compare it to null  parm    null  and if not null compare to zero

User · Answer

This is really just an expansion of Freddy Rios  accepted answer only using Generics   public static bool IsNullOrDefault lt T gt  this Nullable lt T gt  value  where T   struct       return default T  Equals  value GetValueOrDefault         public static bool IsValue lt T gt  this Nullable lt T gt  value  T valueToCheck  where T   struct       return valueToCheck Equals  value    valueToCheck        NOTE we don t need to check default T  for null since we are dealing with either value types or structs  This also means we can safely assume T valueToCheck will not be null  Remember here that T  is shorthand Nullable lt T gt  so by adding the extension to Nullable lt T gt  we get the method in int   double   bool  etc   Examples   double  x   null  x IsNullOrDefault      true  int  y   3  y IsNullOrDefault      false  bool  z   false  z IsNullOrDefault      true

User · Answer

Don t forget  for strings  you can always use   String IsNullOrEmpty str    Instead of   str  null    str

User · Answer

Although I quite like the accepted answer  I think that  for completeness  this option should be mentioned as well   if  item Rate GetValueOrDefault      0        This solution   does not require an additional method  is faster than all the other options  since GetValueOrDefault is a single field read operation   and reads easier than   item Rate    0     0   this might be a matter of taste  though          This should not influence your decision  though  since these kinds of micro-optimization are unlikely to make any difference

User · Answer

Using generics    static bool IsNullOrDefault lt T gt  T value        return object Equals value  default T             double d   0  IsNullOrDefault d      true MyClass c   null  IsNullOrDefault c      true   If T it s a reference type  value will be compared with null   default T     otherwise  if T is a value type  let s say double  default t  is 0d  for bool is false  for char is   0  and so on

User · Answer

class Item     bool IsNullOrZero  get return   this Rate    0     0

User · Answer

I like if   item Rate    0     0         Update 1   You could also define an extension method like   public static bool IsNullOrValue this double  value  double valueToCheck        return  value  valueToCheck     valueToCheck      And use it like this    if item IsNullOrValue 0          but you don t get much from it

User · Answer

public static bool nz object obj        return obj    null    obj Equals Activator CreateInstance obj GetType

User · Answer

One step further from Joshua Shannon s nice answer  Now with preventing boxing unboxing   public static class NullableEx       public static bool IsNullOrDefault lt T gt  this T  value          where T   struct               return EqualityComparer lt T gt  Default Equals value GetValueOrDefault    default T

User · Answer

is there a better way    Well  if you are really looking for a better way  you can probably add another layer of abstraction on top of Rate   Well here is something I just came up with using Nullable Design Pattern    using System  using System Collections Generic   namespace NullObjectPatternTest       public class Program               public static void Main string   args                        var items   new List                                                               new Item RateFactory Create 20                                    new Item RateFactory Create null                                               PrintPricesForItems items                      private static void PrintPricesForItems IEnumerable items                        foreach  var item in items                  Console WriteLine  Item Price   0 C    item GetPrice                          public abstract class ItemBase               public abstract Rate Rate   get            public int GetPrice                            There is NO need to check if Rate    0 or Rate    null             return 1   Rate Value                       public class Item   ItemBase               private readonly Rate  Rate          public override Rate Rate   get   return  Rate              public Item Rate rate     Rate   rate               public sealed class RateFactory               public static Rate Create int  rateValue                        if   rateValue    rateValue    0                   return new NullRate                return new Rate rateValue                        public class Rate               public int Value   get  set            public virtual bool HasValue   get   return  Value   0               public Rate int value    Value   value               public class NullRate   Rate               public override bool HasValue   get   return false              public NullRate     base 0

User · Answer

I agree with using the    operator    If you re dealing with strings use if String IsNullOrEmpty myStr

[c#] Nullable types: better way to check for null or zero in c#

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