I have run into an odd casting issue while using generics. The following code will throw an InvalidCastException
even though clearly an int
can be cast to a double
. Can anyone explain this behaviour and how to bypass it?
public class TestClass<T>
{
public T Cast(object o)
{
return (T)o;
}
}
public void Main()
{
TestClass<double> w = new TestClass<double>();
double x = w.Cast(10);
}
Edit:
Since I am in .net 4.0 land anyway I have changed it to use 'dynamic' instead of 'object' and everything works as expected. Appreciate all the spot-on and quick replies.
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But an object
can't be cast to a double
. The o
parameter takes an object
, not an int
.
For example, the following code fails with an InvalidCastException
:
object o = 1000;
double x = (double)o;
You can use TypeConverter to convert variables
public class TestClass<T>
{
public T Cast(object o)
{
TypeConverter converter = TypeDescriptor.GetConverter(o);
if (converter.CanConvertTo(typeof(T)))
{
var result = converter.ConvertTo(o, typeof(T));
return (T)result;
}
throw new InvalidCastException(
string.Format("Cannot convert from {0} to {1}", o.GetType().Name, typeof(T).Name));
}
}
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