Handle DBNull in C#

Question

Is there a better/cleaner way to do this?

int stockvalue = 0;
if (!Convert.IsDBNull(reader[\"StockValue\"]))
    stockvalue = (int)reader[\"StockValue\"];


        

Answer 1

The way I handle this is

int? stockvalue = reader["StockValue"] as int?;

Very simple, clean and one line. If for some reason I absolutely can't have a null value (which I find poor reasoning for usually since I'd rather know if a value has meaning or if it was unitialized for a primitive type) I would do:

int stockvalue = (reader["StockValue"] as int?).GetValueOrDefault(-1);

Answer 2

Yes you can use int? This way you can have a default value of null instead of 0. Since the result of stockvalue could potentially be 0 there isn't confusion as to whether the database was 0 or null. For instance like this (pre nullable) we had a default initialization of -1 to represent no value was assigned. Personally, I thought this was a little dangerous because if you forget to set it to -1, there is a data corruption issue that can be really difficult to track down.

http://msdn.microsoft.com/en-us/library/2cf62fcy(VS.80).aspx

int? stockvalue = null;

if (!Convert.IsDBNull(reader["StockValue"]))
    stockvalue = (int)reader["StockValue"];

//Then you can check 

if(stockValue.HasValue)
{
  // do something here.
}

Answer 3

The shortest (IMHO) is:

int stockvalue = (reader["StockValue"] as int?) ?? 0;

Explanation:

• If reader["StockValue"] is of type int, the value will be returned, and the "??" operator will return the result
• If reader["StockValue"] is NOT of type int (e.g. DBNull), null will be returned, and the "??" operator will return the value 0 (zero).

Answer 4

int? stockValue = reader["StockValue"] == null || reader["StockValue"] == DBNull.Value ? null : (int?)reader["StockValue"];

Answer 5

You could do this conversion directly in your DB-query, thus avoiding the special case alltogether.

But I wouldn't call that 'cleaner', unless you can consistently use that form in your code, since you would lose information by returning '0' instead of NULL from the DB.

Answer 6

While it's convenient to reference reader["StockValue"], it's not very efficient. It's also not strongly-typed, as it returns type object.

Instead, within your code, do something like this:

int stockValueOrdinal = reader.GetOrdinal("StockValue");
int? stockValue = reader.IsDbNull(stockValueOrdinal) ?
    null : 
    reader.GetInt32(stockValueOrdinal);

Of course, it's best to get all of the ordinals at one time, then use them throughout the code.