Casting vs Converting an object toString, when object really is a string
The two are intended for different purposes. The ToString method of any object is supposed to return a string representation of that object. Casting is quite different, and the 'as' key word performs a conditional cast, as has been said. The 'as' key word basically says "get me a reference of this type to that object if that object is this type" while ToString says "get me a string representation of that object". The result may be the same in some cases but the two should never be considered interchangeable because, as I said, they exist for different purposes. If your intention is to cast then you should always use a cast, NOT ToString.
from http://www.codeguru.com/forum/showthread.php?t=443873
see also http://bytes.com/groups/net-c/225365-tostring-string-cast
If you know it is a String
then by all means cast it to a String
. Casting your object is going to be faster than calling a virtual method.
Edit: Here are the results of some benchmarking:
============ Casting vs. virtual method ============
cast 29.884 1.00
tos 33.734 1.13
I used Jon Skeet's BenchmarkHelper
like this:
using System;
using BenchmarkHelper;
class Program
{
static void Main()
{
Object input = "Foo";
String output = "Foo";
var results
= TestSuite.Create("Casting vs. virtual method", input, output)
.Add(cast)
.Add(tos)
.RunTests()
.ScaleByBest(ScalingMode.VaryDuration);
results.Display(ResultColumns.NameAndDuration | ResultColumns.Score,
results.FindBest());
}
static String cast(Object o)
{
return (String)o;
}
static String tos(Object o)
{
return o.ToString();
}
}
So it appears that casting is in fact slightly faster than calling ToString()
.