Illegal typecast exception?

  • Thread starter Thread starter Ray Mitchell
  • Start date Start date
R

Ray Mitchell

Hello,

I have an array list whose elements are the following
types:

float
int
float
int
....etc.

I have the following code dealing with the elements:

float f0 = (float)list[0];
float f1 = (float)list[1];
float f2 = (float)list[2];
float f3 = (float)list[3];

Although the code compiles fine, I get a "Specified cast
is not valid." runtime exception on f1 and f3. I can fix
it by doing the following:

float f1 = (float)(int)list[1];
float f3 = (float)(int)list[3];

However, that's rediculous since in reality my code is a
loop that merely does something like:

for (i = 0; i < list.Count; ++i)
floatArray = (float)list;

What's going on?

Thanks,
Ray Mitchell
 
Ray Mitchell said:
I have an array list whose elements are the following
types:

float
int
float
int
...etc.

I have the following code dealing with the elements:

float f0 = (float)list[0];
float f1 = (float)list[1];
float f2 = (float)list[2];
float f3 = (float)list[3];

Although the code compiles fine, I get a "Specified cast
is not valid." runtime exception on f1 and f3. I can fix
it by doing the following:

float f1 = (float)(int)list[1];
float f3 = (float)(int)list[3];

However, that's rediculous since in reality my code is a
loop that merely does something like:

for (i = 0; i < list.Count; ++i)
floatArray = (float)list;

What's going on?
Click to expand...


What's going on is that you're trying to unbox an int as a float, and
that won't work as you've already seen. What you can do is:

for (int i=0; i < list.Count; i++)
{
if (list is float)
{
floatArray = (float)list;
}
else if (list is int)
{
floatArray = (float)(int)list;
}
else
{
// Error handling
}
}

or you could use:

for (int i=0; i < list.Count; i++)}
{
floatArray = Convert.ToSingle(list);
}
 
Ray said:
float f1 = (float)(int)list[1];
float f3 = (float)(int)list[3];
Click to expand...

Since you'll be casting to them all to float in the end, why not cast
them to float as you add them to the array?

--
There are 10 kinds of people. Those who understand binary and those who
don't.

http://code.acadx.com
(Pull the pin to reply)
 
Hi,
You have boxed a value type. When unboxing the type the following rule is
applied

"For an unboxing conversion to a given value type to succeed at run time,
the value of the source argument must be a reference to an object that was
previously created by boxing a value of that value type. If the source
argument is null or a reference to an incompatible object, an
InvalidCastException is thrown."

According to the rule your unboxing "int" type to a "float" and they are
not the same, so the exception is thrown. For more details read read about
Boxing/Unboxing.

The following works for me...

for (i = 0; i < list.Count; ++i)
floatArray = System.Convert.ToSingle(list);

Hope that helps.

_Rakesh


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Subject: Illegal typecast exception?
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Hello,

I have an array list whose elements are the following
types:

float
int
float
int
...etc.

I have the following code dealing with the elements:

float f0 = (float)list[0];
float f1 = (float)list[1];
float f2 = (float)list[2];
float f3 = (float)list[3];

Although the code compiles fine, I get a "Specified cast
is not valid." runtime exception on f1 and f3. I can fix
it by doing the following:

float f1 = (float)(int)list[1];
float f3 = (float)(int)list[3];

However, that's rediculous since in reality my code is a
loop that merely does something like:

for (i = 0; i < list.Count; ++i)
floatArray = (float)list;

What's going on?

Thanks,
Ray Mitchell
Click to expand...



Rakesh, EFT.

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