Passing Generic Input object to a method C# -

i have method abc() gets called 2 different places in application. , both places have different objects of class implemented common interface "idestination".

my 2 classes , interface looking this:

public class classa: idestination {         public string var1 { get; set; }             public string var2 { get; set; }             public string var3 { get; set; } }  public class classb: idestination {         public string var1 { get; set; }         public string var2 { get; set; }         public string var3 { get; set; }         public string var4 { get; set; }         public string var5 { get; set; } }  public interface idestination {         string var1 { get; set; }         string var2 { get; set; } } 

as of method abc() accepts object of classa, want can accept object of classb. have made method defination generic below:

public string abc<t>(t obj) {  } 

but, problem inside abc method want access properties of classes (classa , classb both).

public string abc<t>(t obj)  {         //some code         obj.var2; //of classa          obj.var4; //of classb         //some code  } 

and can't allowed changes in interface.

how can achieve this? not want create method handling different class objects. idea?

you should definitly re-think design. when method accepts instances of interface should work all types, not set. imagine create third type implements interface. have re-implement whole method support this. therefor properties should defined on interface instead of class-level , can accessed within method.

however if have use current approach can cast appropriate type:

classa = obj classa; if (a != null) a.var2 = ... // fail if user provides instance of classc implements interface else ((classb)obj).var4 = ...    

for work need constraint on gegernic parameter:

public string abc<t>(t obj) t : idestination