SqlCommand.ExecuteScalarAsync(CancellationToken) Method

Definition

Namespace:

Microsoft.Data.SqlClient

Assembly:

Microsoft.Data.SqlClient.dll

Package:

Microsoft.Data.SqlClient v5.2.0

An asynchronous version of ExecuteScalar() , which executes the query asynchronously and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.

The cancellation token can be used to request that the operation be abandoned before the command timeout elapses. Exceptions will be reported via the returned Task object.

public:
 override System::Threading::Tasks::Task<System::Object ^> ^ ExecuteScalarAsync(System::Threading::CancellationToken cancellationToken);

public override System.Threading.Tasks.Task<object> ExecuteScalarAsync (System.Threading.CancellationToken cancellationToken);

override this.ExecuteScalarAsync : System.Threading.CancellationToken -> System.Threading.Tasks.Task<obj>

Public Overrides Function ExecuteScalarAsync (cancellationToken As CancellationToken) As Task(Of Object)

Parameters

cancellationToken

CancellationToken

The cancellation instruction.

Returns

Task<Object>

A task representing the asynchronous operation.

Exceptions

ArgumentException

An invalid CommandBehavior value.

InvalidCastException

A SqlDbType other than Binary or VarBinary was used when Value was set to Stream . For more information about streaming, see SqlClient Streaming Support.

-or-

A SqlDbType other than Char, NChar, NVarChar, VarChar, or Xml was used when Value was set to TextReader .

-or-

A SqlDbType other than Xml was used when Value was set to XmlReader .

InvalidOperationException

Calling ExecuteScalarAsync(CancellationToken) more than once for the same instance before task completion.

-or-

The SqlConnection closed or dropped during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

SqlException

SQL Server returned an error while executing the command text.

-or-

A timeout occurred during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

IOException

An error occurred in a Stream , XmlReader or TextReader object during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

ObjectDisposedException

The Stream , XmlReader or TextReader object was closed during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

Remarks

For more information about asynchronous programming in the .NET Framework Data Provider for SQL Server, see Asynchronous Programming.

Note

For long running queries on the server, consider using ExecuteScalar due to a known issue with canceling queries via a cancellation token. Also, consider canceling execution using the Cancel method.