指定的强制转换无效-十进制

Question

I'm trying to declare a decimal number which will take the value of dr["index"] or the value null if dr["index"] is null.

Here is my line of code :

Decimal number = (Decimal)(dr["index"] ?? 0);

I got the following error :

System.Invalid.CastException : 'Specified cast is not valid' 

Would you know how to fix that problem ?

Answer 1

I'd go with in case of DBNull.Value:

Convert.ToDecimal(dr["index"] == DBNull.Value ? 0m : dr["index"])

or in case of null value:

Convert.ToDecimal(dr["index"] ?? 0m)

If dr[index] can only be a numeric value.

Answer 2

I recommend to use Decimal.TryParse instead:

Decimal d = 0;
if(Decimal.TryParse(dr["index"].ToString(), out d)) {
// Do some stuff here...
}
else {
// Connot Parse, do some other stuff...
}