IsDBNullAsync(Int32,CancellationToken) Method
In This Topic
An asynchronous version of System.Data.Common.DbDataReader.IsDBNull(System.Int32), which gets a value that indicates whether the column contains non-existent or missing values. Optionally, sends a notification that operations should be cancelled.
Syntax
'Declaration
Public Overloads Function IsDBNullAsync( _
ByVal As System.Integer, _
ByVal As System.Threading.CancellationToken _
) As System.Threading.Tasks.Task(Of Boolean)
'Usage
Dim instance As VistaDBDataReader
Dim ordinal As System.Integer
Dim cancellationToken As System.Threading.CancellationToken
Dim value As System.Threading.Tasks.Task(Of Boolean)
value = instance.IsDBNullAsync(ordinal, cancellationToken)
public System.Threading.Tasks.Task<bool> IsDBNullAsync(
System.int ,
System.Threading.CancellationToken
)
Parameters
- ordinal
- The zero-based column to be retrieved.
- cancellationToken
- The cancellation instruction, which propagates a notification that operations should be canceled. This does not guarantee the cancellation. A setting of CancellationToken.None makes this method equivalent to System.Data.Common.DbDataReader.IsDBNullAsync(System.Int32). The returned task must be marked as cancelled.
Return Value
true if the specified column value is equivalent to DBNull otherwise false.
Exceptions
| Exception | Description |
|---|
| System.InvalidOperationException | The connection drops or is closed during the data retrieval.
-or-
The System.Data.Common.DbDataReader is closed during the data retrieval.
-or-
There is no data ready to be read (for example, the first System.Data.Common.DbDataReader.Read hasn't been called, or returned false).
-or-
Trying to read a previously read column in sequential mode.
-or-
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. |
| System.IndexOutOfRangeException | Trying to read a column that does not exist. |
Requirements
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
See Also