Using Case Switch and GetType to determine the object

Question

Possible Duplicate  C  - Is there a better alternative than this to    switch on type       If you want to switch on a type of object  what is the best way to do this  Code snippet private int GetNodeType NodeDTO node        switch  node GetType                   case typeof CasusNodeDTO               return 1          case typeof BucketNodeDTO               return 3          case typeof BranchNodeDTO               return 0          case typeof LeafNodeDTO               return 2          default              return -1           I know this doesn t work that way  but I was wondering how you could solve this  Is an if else statement appropriate in this case  Or do you use the switch and add  ToString   to the type

User · Answer

Depending on what you are doing in the switch statement  the correct answer is polymorphism  Just put a virtual function in the interface base class and override for each node type

User · Answer

If I really had to switch on type of object  I d use  ToString    However  I would avoid it at all costs  IDictionary lt Type  int gt  will do much better  visitor might be an overkill but otherwise it is still a perfectly fine solution

User · Answer

You can do this   function void PrintType Type t     var t   true   new Dictionary lt Type  Action gt       typeof bool        gt  Console WriteLine  bool         typeof int         gt  Console WriteLine  int       t GetType           It s clear and its easy  It a bit slower than caching the dictionary somewhere   but for lots of code this won t matter anyway

User · Answer

I actually prefer the approach given as the answer here  Is there a better alternative than this to   39 switch on type  39    There is however a good argument about not implementing any type comparison methids in an object oriented language like C   You could as an alternative extend and add extra required functionality using inheritance   This point was discussed in the comments of the authors blog here  http   blogs msdn com b jaredpar archive 2008 05 16 switching-on-types aspx 8553535  I found this an extremely interesting point which changed my approach in a similar situation and only hope this helps others   Kind Regards  Wayne

User · Answer

You can do this   if  node is CasusNodeDTO              else if  node is BucketNodeDTO                    While that would be more elegant  it s possibly not as efficient as some of the other answers here

User · Answer

One approach is to add a pure virtual GetNodeType   method to NodeDTO and override it in the descendants so that each descendant returns actual type

User · Answer

I d just use an if statement  In this case    Type nodeType   node GetType    if  nodeType    typeof CasusNodeDTO       else        The other way to do this is   if  node is CasusNodeDTO      else       The first example is true for exact types only  where the latter checks for inheritance too

User · Answer

I m faced with the same problem and came across this post  Is this what s meant by the IDictionary approach   Dictionary lt Type  int gt  typeDict   new Dictionary lt Type  int gt         typeof int  0        typeof string  1        typeof MyClass  2      void Foo object o        switch  typeDict o GetType                   case 0              Print  I m a number                 break          case 1              Print  I m a text                 break          case 2              Print  I m classy                 break          default              break            If so  I can t say I m a fan of reconciling the numbers in the dictionary with the case statements   This would be ideal but the dictionary reference kills it   void FantasyFoo object o        switch  typeDict o GetType                   case typeDict typeof int                Print  I m a number                 break          case typeDict typeof string                Print  I m a text                 break          case typeDict typeof MyClass                Print  I m classy                 break          default              break            Is there another implementation I ve overlooked

User · Answer

This won t directly solve your problem as you want to switch on your own user-defined types  but for the benefit of others who only want to switch on built-in types  you can use the TypeCode enumeration   switch  Type GetTypeCode node GetType           case TypeCode Decimal             Handle Decimal         break       case TypeCode Int32             Handle Int32         break

User · Answer

In the MSDN blog post Many Questions  switch on type is some information on why  NET does not provide switching on types   As usual - workarounds always exists   This one isn t mine  but unfortunately I have lost the source  It makes switching on types possible  but I personally think it s quite awkward  the dictionary idea is better      public class Switch           public Switch Object o                    Object   o                 public Object Object   get  private set                 lt summary gt        Extensions  because otherwise casing fails on Switch  null        lt  summary gt    public static class SwitchExtensions           public static Switch Case lt T gt  this Switch s  Action lt T gt  a              where T   class                   return Case s  o   gt  true  a  false                  public static Switch Case lt T gt  this Switch s  Action lt T gt  a             bool fallThrough  where T   class                   return Case s  o   gt  true  a  fallThrough                  public static Switch Case lt T gt  this Switch s            Func lt T  bool gt  c  Action lt T gt  a  where T   class                   return Case s  c  a  false                  public static Switch Case lt T gt  this Switch s            Func lt T  bool gt  c  Action lt T gt  a  bool fallThrough  where T   class                   if  s    null                            return null                         T t   s Object as T            if  t    null                            if  c t                                     a t                     return fallThrough   s   null                                         return s                Usage    new Switch foo        Case lt Fizz gt            action   gt    doingSomething   FirstMethodCall             Case lt Buzz gt            action   gt    return false

[c#] Using Case/Switch and GetType to determine the object

Examples related to c#

Examples related to .net

Examples related to reflection

Examples related to switch-statement

Examples related to case