Whats Best Convert.ToSting() or Just Concatenate with an Empty String?

Question

var item = "" + dr["someString"];

Or

var item = Convert.ToString(dr["somestring"]);

What are the performance implications of the above examples?

Marc Gravell · Accepted Answer · 2012-03-09T11:52:13.883

8

How about:

var item = (string)dr["someString"] ?? "";

which avoids an unnecessary concatenation, an unnecessary virtual call, and avoids the risk of calling a method on a null reference. It isn't clear what dr is in this context; if it is a data-reader (IDataReader etc) you might need:

int index = dr.GetOrdinal("someString");
var item = dr.IsDBNull(index) ? "" : dr.GetString(index);

or in the case of a DataTable, something involving DataRow.IsNull.

edited Mar 09 '12 at 11:52

answered Mar 09 '12 at 11:44

Marc Gravell

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In this example its a DataRow – Leigh Ciechanowski Mar 09 '12 at 11:48
@Leigh of course, I'm not a fan of `DBNull` in the first place, but in the context of a `DataRow` you *could* use `dr.IsNull(...)`. It won't change the answer, but [some related notes](http://stackoverflow.com/questions/4958379/what-is-the-difference-between-null-and-system-dbnull-value/9632050#9632050) that you might find interesting. – Marc Gravell Mar 09 '12 at 11:51
@Leigh as an aside, it also shows the importance of including all relevant context in a question; in this case, it **really matters** what `dr` is defined as, so it would be useful to volunteer that in the question ;p – Marc Gravell Mar 09 '12 at 11:53
Cool so I can conclude that casting the object to a sting and checking if its null will be better for performance than just concatenating the object with an empty string? – Leigh Ciechanowski Mar 09 '12 at 12:09
@LeighCiechanowski well, the concat involves extra unnecessary steps - however, in the case of DataRow it won't be `null`, but `DbNull`, which is more work – Marc Gravell Mar 09 '12 at 12:16
hmm yes the code doesn't seem as readable I have now got dr.IsNull("someString") ? "" :(string)dr["someString"] which seems a lot less readable compared to "" + dr["someString"] which I'm tempted to go with unless its going to be bad for performance... I'm not really worried about performance because this is not going to loop or anything I was just curious. – Leigh Ciechanowski Mar 09 '12 at 12:29

score 2 · Answer 2 · edited Mar 09 '12 at 12:27

2

Whats wrong with dr["someString"].ValueOrEmpty()?

As for your original question. The performance will not matter. I promise you that there are several other areas that can be optimized which gives a lot better performance gain.

Write the most readable code. And do not optimize until it's proven that you need to.

Update:

public static class StringExtensions
{
    public static string ValueOrEmpty(this object obj)
    {
        return obj == null ? "" : obj.ToString();
    }
}

edited Mar 09 '12 at 12:27

kaj

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answered Mar 09 '12 at 11:43

jgauffin

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Yes or doing it that way which is best? – Leigh Ciechanowski Mar 09 '12 at 11:44
@Mark, If `dr` is a DataRow, wouldn't dr["someThing"] return DBNull instead of null? – zmbq Mar 09 '12 at 11:45
@zmbq that depends entirely on what `dr` is, which is not clear in the question. I actually wondered if it was "data reader", and have illustrated something similar in my answer. – Marc Gravell Mar 09 '12 at 11:47

Whats Best Convert.ToSting() or Just Concatenate with an Empty String?

2 Answers2