Better way to cast object to int

Question

Hi, This is probably trivial, but I can't think of a better way to do it. I have a COM object that returns a variant which becomes an object in C#. The only way I can get this into an int is

int test = int.Parse(string.Format("{0}", myobject))

Is there a cleaner way to do this? Thanks

Answer 1

Maybe Convert.ToInt32.

Watch out for exception, in both cases.

Answer 2

Use Int32.TryParse as follows.

  int test;
  bool result = Int32.TryParse(value, out test);
  if (result)
  {
     Console.WriteLine("Sucess");         
  }
  else
  {
     if (value == null) value = ""; 
     Console.WriteLine("Failure");
  }

Answer 3

Convert.ToInt(myobject);

this will handle the case where myobject is null and return 0, instead of throwing an exception.

Answer 4

There's also TryParse.

From MSDN:

private static void TryToParse(string value)
   {
      int number;
      bool result = Int32.TryParse(value, out number);
      if (result)
      {
         Console.WriteLine("Converted '{0}' to {1}.", value, number);         
      }
      else
      {
         if (value == null) value = ""; 
         Console.WriteLine("Attempted conversion of '{0}' failed.", value);
      }
   }

Answer 5

The cast (int) myobject should just work.

If that gives you an invalid cast exception then it is probably because the variant type isn't VT_I4. My bet is that a variant with VT_I4 is converted into a boxed int, VT_I2 into a boxed short, etc.

When doing a cast on a boxed value type it is only valid to cast it to the type boxed. Foe example, if the returned variant is actually a VT_I2 then (int) (short) myObject should work.

Easiest way to find out is to inspect the returned object and take a look at its type in the debugger. Also make sure that in the interop assembly you have the return value marked with MarshalAs(UnmanagedType.Struct)