Using SqlDataReader

Question

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?

You 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, Apr 09 '15 at 13:45

Andrey Korneyev · Accepted Answer · 2015-04-09T13:55:22.417

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 GetValue instead of GetString and 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.

Just another small question how would I read an `int` value using the first example? — Izzy, Apr 09 '15 at 14:11
@Code well , for example you can use `Convert.ToInt32(reader["Test"]);` — Andrey Korneyev, Apr 09 '15 at 14:12

score 0 · Answer 2 · edited May 23 '17 at 10:24

0

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

edited May 23 '17 at 10:24

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answered Apr 09 '15 at 13:46

Juergen Gutsch

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Using SqlDataReader

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