GetType syntax

Replies to This Discussion

Permalink Reply by Giulio Piacentino on February 3, 2011 at 9:45am

Hi Raf,

 

sure. You use this pattern when you do not know the type, for example:

object myObj = "Hello";

if(myObj is string)
{
   Print("It's a string.");


   //We know it's a string, so we migth want to cast to it
   string myStr = (string)myObj;

   //Now we can print it
   Print(myStr);
}

 

- Giulio

________________

giulio@mcneel.com
McNeel Europe, Barcelona

myStr

Permalink Reply by Giulio Piacentino on February 3, 2011 at 9:51am

"is" is a C# keyword. Alternatively, you can use GetType().

if(myObj.GetType() == typeof(string))

- Giulio

________________

giulio@mcneel.com
McNeel Europe, Barcelona

Permalink Reply by raf2205 on February 3, 2011 at 12:07pm

thank you !

Permalink Reply by Steve Baer on February 3, 2011 at 12:49pm

Another alternative in C# would be the "as" keyword which will attempt to cast if the type is a match

 

string mystr = myObj as string;

if( mystr!=null )

{

  Print("It's a string!");

  Print(mystr);

}

Permalink Reply by Giulio Piacentino on February 3, 2011 at 1:56pm

Now (thanks Steve) we showed three ways, so let's have a look at some differences. My preference is to:

1) use is if I do not need to cast afterwards, as this method is readable. Like as and casts, it also checks for compatible types (for example LineCurve that inherits from Curve):

if (myObj is Curve)
{
   Print("It's a curve (and not null).");

2) use as if I'd otherwise need to have the object cast afterwards. This is faster as it avoids the double cast (once for is, then the real ()cast), but might add more variables in the method and cannot be used with value types (structs):

string mystr = myObj as string;
if (mystr != null)
{

3) use GetType() == typeof() if you want to check for the precise type (or maybe with structs, as they cannot have inherited types). There are also some rare cases with generic constrains that benefit from this. Eventually, check against null beforehand, as GetType() is an instance method:

if(myObj.GetType() == typeof(T))
{


I hope this helps,

- Giulio
____________

giulio@mcneel.com
McNeel Europe, Barcelona

Permalink Reply by raf2205 on February 3, 2011 at 4:46pm

sure it helps :) thx