I have CustomerID declared as
int? CustomerID=null;
I am checking null values while reading DataReader
Id = reader["CustomerId"] is DBNull ? null :Convert.ToInt32(reader["CustomerID"]);
It is throwing
Type of conditional expression cannot be determined because there
is no implicit conversion between '<null>' and 'int'
What is the problem with the Conversion?
I think you need to do it this way:
if(! reader.IsDBNull(reader.GetOrdinal("CustomerId"))
{
Id = Convert.ToInt32(reader["CustomerID"]);
}
else
{
Id = NULL;
}
You need to use the .IsDBNull method on the reader to determine ahead of time if a column is NULL - if it is, don't even read the value from the reader.
Change your conditon to
reader["CustomerId"] == DBNull.Value
A ?: conditional expression cannot evaluate to two different types on the true and false condition. I think a cast (int?)null should work.
The problem (assuming that Id is declared properly) is that the conditional statement infers the result type from the true result. In your case, that type is null. It then will try to cast the second type to the same as the first...and there is no cast from int to null.
The solution is to cast the true expression to the desired type:
Id = reader["CustomerId"] == DBNull.Value ?
(int?) null :
Convert.ToInt32(reader["CustomerID"]);
Try this
Id = reader["CustomerId"] is DBNull ? (int?)null : Convert.ToInt32(reader["CustomerID"]);
the types of both parts of the ?: need to be explicit
What's happening is your code is incorrectly evaluating and trying to do the Convert function.
Its readding reader["CustomerId"] is DBNull which it isn't its really a DBNull.Value so then it attempts to do Convert.ToInt32("<null>") and crashes. You need to fix your if statement, and add a (int ?) cast.
It should be:
Id = reader["CustomerId"] is DBNull.Value ? (int?) null :Convert.ToInt32(reader["CustomerID"]);
