Re: converting/casting before submitting

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From: Karl Seguin (_at_)
Date: 12/09/04 

Date: Thu, 9 Dec 2004 17:19:06 -0500

SqlParameter.Value is of type Object, which suggest that everything is taken
care of internally and casting is indeed not required. Of course, to
confirm this assumption, we get Reflector and look at the disassembled code
for how SqlParameter.set_Value works.

We see that it calls something called SetTypeInfoFromComType which in turn
calls a static function GetMetaType of an internal class named MetaType.
This is the function that seems to be doing all the work..stuff like:

case TypeCode.DBNull:
   throw ADP.InvalidDataType(TypeCode.DBNull);
case TypeCode.Boolean:
  return MetaType.metaTypeMap[2];
case TypeCode.Char:
  throw ADP.InvalidDataType(TypeCode.Char);
case TypeCode.SByte:
  throw ADP.InvalidDataType(TypeCode.SByte);
case TypeCode.Byte
  return MetaType.metaTypeMap[20];
case TypeCode.Int16
 return MetaType.metaTypeMap[0x10];

Also, FIY, TinyInt is a value from 0-255, which in .Net maps to a Byte and
not an Int16.

Karl 

-- 
MY ASP.Net tutorials
http://www.openmymind.net/
"djc" <noone@nowhere.com> wrote in message
news:%23cNeOYj3EHA.708@TK2MSFTNGP11.phx.gbl...
> I have typically always used one of the VB CType functions (not CType
itself
> but CInt, CString, etc...) to cast/convert an input value to its proper
type
> before passing it as a parameter to a SQL stored procedure. I recently
came
> accross one I did not know how to handle though... TinyInt. I have an SQL
> field of type TinyInt which is an 8bit integer. I came accross a ToInt16()
> vb function but not one for an 8 bit 'TinyInt'. So I next just went ahead
> and tried to submit the value as is to the stored procedure to see if
there
> would be a problem. The value is a string (from a
> dropdownListBox.SelectedItem.Text). To my suprise there was no error. It
> took the value fine. The SQL stored procedure was expecting a TinyInt as
> declared in the stored procedure. ??
>
> 1) Is there some type of auto-conversion in place? have I been wasting
time
> and/or slowing performance converting/casting myself all this time?
>
> 2) does the SQL stored procedure convert it itself since that is what was
> declared within it?
>
> any info would be greatly appreciated. Thanks.
>
>

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