I've seen some people use SqlDataReader to get data from database as
reader["Test"].ToString();
...
and others as
reader.GetString(0);
...
Is there any difference in any way? Or does it come down to personal preference?
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1You are better off using the first example when doing this. If column order changes you have alot of potential for error. It is usually best to avoid hard coded indexing at all times.Jeffrey Wieder– Jeffrey Wieder2015-04-09 13:45:04 +00:00Commented Apr 9, 2015 at 13:45
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2 Answers
Pretty obvious:
- first one should be used when you know column names of data returned. For me it is preferred to second since column order can be changed. Also in this case you can convert datatype of returned objects later.
- second one is preferable when you don't know these names (or maybe even columns has no names) but you're ensured in exact datatype of columns you're accessing. If column datatype will be mismatched - you'll get exception. So if you can't access colmn by name and not sure in exact datatype it's better to use
GetValueinstead ofGetStringand other typed methods. For me this way of accessing data is really useful only if your query something like 'select x, sum(y) from sometable` - i.e. second column has no name so you can't access it by name.
Considered to performance - accessing by name takes slightly more time since accessing by index internally is
public override object this[int i]
{
get
{
return this.GetValue(i);
}
}
and accessing by name is
public override object this[string name]
{
get
{
return this.GetValue(this.GetOrdinal(name));
}
}
So accessing by name invokes GetOrdinal first.
But in real application this difference is absolutely negligable.
3 Comments
Izzy
Just another small question how would I read an
int value using the first example?
Andrey Korneyev
@Code well , for example you can use
Convert.ToInt32(reader["Test"]);Izzy
Right, Thanks once again :)
It always makes sense to use field names instead of indices, because you could get some troubles, if the order of the fields in the SQL statement changes.
I prefer using this way: DataReader.GetString() via columnname
