Is a cast to string always possible without exception?

[geronimi]

I wonder when an exception raises when I do this:

string str= (string)ds.Tables[0].Rows[0]["CODE"]

The row is always filled with data

If there is a dbnull.value in it, does it raises an error?
And for other data?

thx

[Jon Skeet [C# MVP]]

geronimi wrote:

I wonder when an exception raises when I do this:

string str= (string)ds.Tables[0].Rows[0]["CODE"]

The row is always filled with data

If there is a dbnull.value in it, does it raises an error?
Yes.
And for other data?

If the value isn't a string, you'll get an exception.

Jon

[geronimi]

So an integer or object will fail? I thought it will make from a 7 a
"7"

If I do string str=Convert.ToString(ds.Tables[0].Rows[0]["CODE"] )
in stead of string str= (string)ds.Tables[0].Rows[0]["CODE"]

does that make any difference?

[Jon Skeet [C# MVP]]

geronimi wrote:

So an integer or object will fail? I thought it will make from a 7 a
"7"
Not with a cast, no.
If I do string str=Convert.ToString(ds.Tables[0].Rows[0]["CODE"] )
in stead of string str= (string)ds.Tables[0].Rows[0]["CODE"]

does that make any difference?

Yes, that should be fine. Or just call ToString().

Jon

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,
"geronimi" <we******@hotmail.com> wrote in message
news:11*********************@i39g2000cwa.googlegro ups.com...

I wonder when an exception raises when I do this:
Whenever the content if not a string or a type that define an explicit
conversion. They are not that much though.

string str= (string)ds.Tables[0].Rows[0]["CODE"]

The row is always filled with data
What kind of data?
If there is a dbnull.value in it, does it raises an error?
YES
try this:
string s = (string) DBNull.Value;
And for other data?

See the first answer, the safest way is first to test for null and assign if
not.

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

[Stoitcho Goutsev \(100\)]

geronimi,

No, that will throw exception if the object is not a string.

You can always use ToString() thought. It will never throw an exception.
--
HTH
Stoitcho Goutsev (100)

"geronimi" <we******@hotmail.com> wrote in message
news:11*********************@i39g2000cwa.googlegro ups.com...

I wonder when an exception raises when I do this:

string str= (string)ds.Tables[0].Rows[0]["CODE"]

The row is always filled with data

If there is a dbnull.value in it, does it raises an error?
And for other data?

thx