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 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 2

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 3

I wrote an extension method several days ago. By using it you could just do:

int? stockvalue = reader.GetValue<int?>("StockValue");

Here's the extension method (modify to fit your needs):

public static class ReaderHelper
{
    public static bool IsNullableType(Type valueType)
    {
        return (valueType.IsGenericType &&
            valueType.GetGenericTypeDefinition().Equals(typeof(Nullable<>)));
    }

    public static T GetValue<T>(this IDataReader reader, string columnName)
    {
        object value = reader[columnName];
        Type valueType = typeof(T);
        if (value != DBNull.Value)
        {
            if (!IsNullableType(valueType))
            {
                return (T)Convert.ChangeType(value, valueType);
            }
            else
            {
                NullableConverter nc = new NullableConverter(valueType);
                return (T)Convert.ChangeType(value, nc.UnderlyingType);
            }
        }
        return default(T);
    }
}