DataReader: Specified cast is not valid (Int32)

Question

Why does SqlDataReader throw an exception when converting 0 to integer?

?dataReader(3)
0 {Short}
    Short: 0
?dataReader.GetInt16(3)
0
?dataReader.GetInt32(         


        

Answer 1

It isn't a convert - it is a cast. The same as:

short x = 0;
object y = x;
int z = (int)y; // BOOM! InvalidCastException Specified cast is not valid.

In both cases, a short is not an int.

If unsure of the type, you might try:

int i = Convert.ToInt32(dataReader.GetValue(3));