C switch on type

Question

Possible Duplicate    C  - Is there a better alternative than this to   39 switch on type  39         C  doesn t support switching on the type of an object  What is the best pattern of simulating this   switch  typeof MyObj       case Type1      case Type2      case Type3

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Update  This got fixed in C  7 0 with pattern matching  switch  MyObj      case Type1 t1       case Type2 t2      case Type3 t3    Old answer   It is a hole in C  s game  no silver bullet yet   You should google on the  visitor pattern  but it might be a little heavy for you but still something you should know about   Here s another take on the matter using Linq  http   community bartdesmet net blogs bart archive 2008 03 30 a-functional-c-type-switch aspx  Otherwise something along these lines could help      nasty   switch MyObj GetType ToString       case  Type1   etc       clumsy    if myObj  is Type1 then if myObj is Type2 then   etc

User · Answer

There is a simple answer to this question which uses a dictionary of types to look up a lambda function  Here is how it might be used   var ts   new TypeSwitch        Case  int x    gt  Console WriteLine  int         Case  bool x    gt  Console WriteLine  bool         Case  string x    gt  Console WriteLine  string      ts Switch 42   ts Switch false   ts Switch  hello      There is also a generalized solution to this problem in terms of pattern matching  both types and run-time checked conditions    var getRentPrice   new PatternMatcher lt int gt         Case lt MotorCycle gt  bike   gt  100   bike Cylinders   10        Case lt Bicycle gt  30        Case lt Car gt  car   gt  car EngineType    EngineType Diesel  car   gt  220   car Doors   20       Case lt Car gt  car   gt  car EngineType    EngineType Gasoline  car   gt  200   car Doors   20       Default 0    var vehicles   new object         new Car   EngineType   EngineType Diesel  Doors   2        new Car   EngineType   EngineType Diesel  Doors   4        new Car   EngineType   EngineType Gasoline  Doors   3        new Car   EngineType   EngineType Gasoline  Doors   5        new Bicycle        new MotorCycle   Cylinders   2        new MotorCycle   Cylinders   3        foreach  var v in vehicles        Console WriteLine  Vehicle of type  0  costs  1  to rent   v GetType    getRentPrice Match v

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I did it one time with a workaround  hope it helps   string fullName   typeof MyObj  FullName   switch  fullName        case  fullName1       case  fullName2       case  fullName3

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See gjvdkamp s answer below  this feature now exists in C   I usually use a dictionary of types and delegates  var  switch   new Dictionary lt Type  Action gt          typeof Type1        gt               typeof Type2        gt               typeof Type3        gt              switch typeof MyType       It s a little less flexible as you can t fall through cases  continue etc  But I rarely do so anyway

User · Answer

I have used this form of switch-case on rare occasion  Even then I have found another way to do what I wanted  If you find that this is the only way to accomplish what you need  I would recommend  Mark H s solution     If this is intended to be a sort of factory creation decision process  there are better ways to do it  Otherwise  I really can t see why you want to use the switch on a type     Here is a little example expanding on Mark s solution  I think it is a great way to work with types     Dictionary lt Type  Action gt  typeTests   public ClassCtor         typeTests   new Dictionary lt Type  Action gt           typeTests typeof int          gt  DoIntegerStuff        typeTests typeof string          gt  DoStringStuff        typeTests typeof bool          gt  DoBooleanStuff       private void DoBooleanStuff          do stuff    private void DoStringStuff           do stuff    private void DoIntegerStuff           do stuff    public Action CheckTypeAction Type TypeToTest        if  typeTests Keys Contains TypeToTest           return typeTests TypeToTest        return null     or some other Action delegate

[c#] C# switch on type

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