C Passing a Generic Object

Question

I want to have a generic print function   PrintGeneric T    in the following case  what am I missing   As always your help insight is appreciated     public interface ITest     public class MyClass1   ITest       public string myvar    hello 1      public class MyClass2   ITest       public string myvar    hello 2      class DoSomethingClass        static void Main                 MyClass1 test1   new MyClass1            MyClass2 test2   new MyClass2             Console WriteLine test1 myvar           Console WriteLine test2 myvar                        Console WriteLine test1 GetType              PrintGeneric test1           PrintGeneric lt test2 GetType   gt  test2                 following doesn t compile     public void PrintGeneric lt T gt  T test                Console WriteLine  Generic       test myvar

User · Accepted Answer

It doesn t compile because T could be anything  and not everything will have the myvar field   You could make myvar a property on ITest   public ITest       string myvar get       and implement it on the classes as a property   public class MyClass1   ITest       public string myvar  get   return  hello 1           and then put a generic constraint on your method   public void PrintGeneric lt T gt  T test  where T   ITest       Console WriteLine  Generic       test myvar       but in that case to be honest you are better off just passing in an ITest   public void PrintGeneric ITest test        Console WriteLine  Generic       test myvar

User · Answer

You cannot access var with the generic   Try something like  Console WriteLine  Generic    0    test     And override ToString method  1    1  http   msdn microsoft com en-us library system object tostring aspx

User · Answer

You re missing at least a couple of things    Unless you re using reflection  the type arguments need to be known at compile-time  so you can t use  PrintGeneric lt test2 GetType   gt        although in this case you don t need to anyway PrintGeneric doesn t know anything about T at the moment  so the compiler can t find a member called T   Options    Put a property in the ITest interface  and change PrintGeneric to constrain T   public void PrintGeneric lt T gt  T test  where T   ITest       Console WriteLine  Generic       test PropertyFromInterface      Put a property in the ITest interface and remove the generics entirely   public void PrintGeneric ITest test        Console WriteLine  Property       test PropertyFromInterface      Use dynamic typing instead of generics if you re using C  4

User · Answer

You need to define something in the interface  such as   public interface ITest       string Name   get        Implement ITest in your classes   public class MyClass1   ITest       public string Name   get   return  Test1          public class MyClass2   ITest       public string Name   get   return  Test2           Then restrict your generic Print function  to ITest   public void Print lt T gt  T test  where T   ITest

User · Answer

try  public void PrintGeneric lt T gt  T test  where T  ITest       Console WriteLine  Generic       test  var       as  Ash Burlaczenko has said you cant name a variable after a keyword  if you reallllly want this prefix with   symbol to escape the keyword

User · Answer

You ll have to provide more information about the generic type T  In your current PrintGeneric method  T might as well be a string  which does not have a var member   You may want to change var to a property rather than a field  public interface ITest       string var   get        And add a constraint where T  ITest to the PrintGeneric method

User · Answer

In your generic method  T is just a placeholder for a type  However  the compiler doesn t per se know anything about the concrete type s  being used runtime  so it can t assume that they will have a var member   The usual way to circumvent this is to add a generic type constraint to your method declaration to ensure that the types used implement a specific interface  in your case  it could be ITest    public void PrintGeneric lt T gt  T test  where T   ITest   Then  the members of that interface would be directly available inside the method  However  your ITest is currently empty  you need to declare common stuff there in order to enable its usage within the method

[c#] C# : Passing a Generic Object

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