DbDataReader.IsDBNullAsync Method (Int32)
An asynchronous version of IsDBNull, which gets a value that indicates whether the column contains non-existent or missing values.
Assembly: System.Data (in System.Data.dll)
The connection drops or is closed during the data retrieval.
The DbDataReader is closed during the data retrieval.
There is no data ready to be read (for example, the first Read hasn't been called, or returned false).
Trying to read a previously read column in sequential mode.
There was an asynchronous operation in progress. This applies to all Get* methods when running in sequential mode, as they could be called while reading a stream.
Trying to read a column that does not exist.