Is there any way to convert from DB.Null to decimal in C#?
Like
Object[] returnvalue = new Object[1];
returnvalue[0] = null;
returnvalue[0] = Convert.ToDecimal(returnvalue[returnvalue.Length - 1]);
Though CLR is saying that DBNull.Value cannot be type casted. Still I want to know is there
any work around? Thanks in advance
How do you expect to cast null to anything? It's null, nothing, nada...
That said, your best bet would be to check for DBNull (or null in the above case) and use/return/whatever default(decimal) instead, though null and DBNull both have a significant semantic difference from just a default value; they are the absence of a value, so this is probably not what you want to do.
There is a big difference between DBNull and null; your example only shows null...
But in answer; not really... what value whould you give it?
You could test and use the default, or use Nullable<decimal> (aka decimal?):
With null (not DBNull)
decimal? valOrNull = (decimal?)returnvalue[0];
or to take DBNull into account:
object val = returnvalue[0];
decimal? valOrNull = (val == null || val is DBNull) ? (decimal?)null
: (decimal?)val; // or convert if it is a string etc
object foo = DBNull.Value;
decimal d = 0;
d = (decimal)(foo as decimal? ?? 0); // handles dbnull fine with default 0
MessageBox.Show(d.ToString());
foo = 1234M;
d = (decimal)(foo as decimal? ?? 0); // handles dbnull fine with default 0
MessageBox.Show(d.ToString());
Have you considered using a nullable-decimal for your return value?
Though you'd still have to explicitly handle DB.Null, as that's different to null, you'd be able to differentiate the cases.
The code might look something like this ...
if (value == DB.Null)
return null;
else return decimal.Parse(value.ToString());
You can simply do this:
Object[] returnvalue = new Object[1];
returnvalue[0] = DBNull.Value; //null from database
returnvalue[0] = returnvalue[0] == DBNull.Value
? null
: (Nullable<decimal>) Convert.ToDecimal(returnvalue[returnvalue.Length - 1]);
If DBNull were to be converted to a Decimal, what value would you expect that decimal to have?
I think there is a Decimal.TryParse() function which would fail more gracefully.
Would this help?
returnvalue[returnvalue.Length - 1] is DBNull ? 0 : (decimal?)returnvalue[returnvalue.Length - 1] ?? 0
We use the below method to cast DBNull fields to decimal values in C#. The case where the field might be null can be catered for when giving the value of the field to the variable using a shorthand if.
cmd.Fill<Entity>(result, a => new Entity()
{
EntityProperty = (decimal)(a["FieldName"] == DBNull.Value ? null : a["FieldName"]),
});
It could looks like this:
private decimal GetDecimal(string v)
{
decimal r = 0.00M;
try {
r = decimal.Round(Convert.ToDecimal(v.Replace("%", "").Replace("zł", "").Replace(" ", "")), 2);
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message.ToString());
}
return r;
}
Calling:
decimal val = GetDecimal(dataTable.Rows[i][j].ToString()),
DBNullin your example? That's just a simplenull.