tinyint, Byte and byte

[Wasim Akram]

Hi,

I have a field "Month" in my SQL server table. The type of this field is
"tinyint".

Now what I am doing in the code is using DataRow to read this field in a
'int' variable.

int month = (int) dataRow["Month"];

But the above line throws exception that the cast is invalid.

After some time i got to know that the type of expression dataRow["Month"]
is System.Byte.

In the documentation it has been mentioned that 'byte' is implicitly
converted to 'int' when assigned/compared with a 'int' variable.

I am able to run my code by modifying it to
int month = (byte) dataRow["Month"];

From this, I concluded that the implicit conversion holds only for
byte-to-int and not for Byte-to-int.
Is this a feature of C#/.Net or, Microsoft just forgot to do a implicit
Byte-to-int conversion?

Because now I have a overhead of finding the actual type mapping between SQL
types and C# types.
Otherwise, what I wanted to do was to cast every integer fields (either int
or tinyint) to int of C#, without bothering about the underlying conversion.

-
wa

[Jon Skeet [C# MVP]]

Wasim Akram <a@b.c> wrote:

I have a field "Month" in my SQL server table. The type of this field is
"tinyint".

Now what I am doing in the code is using DataRow to read this field in a
'int' variable.

int month = (int) dataRow["Month"];

But the above line throws exception that the cast is invalid.

After some time i got to know that the type of expression dataRow["Month"]
is System.Byte.
No. The type of that expression is Object. The type of the value
returned by that expression may happen to be System.Byte in your case,
but that's a different matter - the compiler doesn't know that.
In the documentation it has been mentioned that 'byte' is implicitly
converted to 'int' when assigned/compared with a 'int' variable.

I am able to run my code by modifying it to
int month = (byte) dataRow["Month"];

From this, I concluded that the implicit conversion holds only for
byte-to-int and not for Byte-to-int.
Is this a feature of C#/.Net or, Microsoft just forgot to do a implicit
Byte-to-int conversion?
There is no difference between Byte and byte - but there *is* a
difference between a boxed byte and an unboxed byte. You have to
explicitly unbox with the exact type, and *then* you can (implicitly or
explicitly) convert the unboxed value to int.
Because now I have a overhead of finding the actual type mapping between SQL
types and C# types.
Otherwise, what I wanted to do was to cast every integer fields (either int
or tinyint) to int of C#, without bothering about the underlying conversion.

You need to unbox to the correct type first.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too