Class AdbExecuteScalarWorker<TResult>

A worker that executes a query on an SQL database and returns a single result value in the ScalarResult property.

The query result (which for value types is boxed in an object) is cast to the TResult type, and if that fails it is first converted (with ChangeType(Object, Type)) and then cast. This handles e.g. the query returning a long but the worker expecting an int.

Also see SQL Database Access.

Inheritance

Object

WorkerParent

WorkerBase

WorkerBase<AdbExecuteScalarWorker<TResult>>

AdbExecuteScalarWorker<TResult>

Implements

IDisposeOnFinished

Inherited Members

WorkerBase<AdbExecuteScalarWorker<TResult>>.AddCompletedCallback(Func<AdbExecuteScalarWorker<TResult>, OutcomeStatus, Task<OutcomeStatus>>)

WorkerBase<AdbExecuteScalarWorker<TResult>>.AddRanCallback(Func<AdbExecuteScalarWorker<TResult>, OutcomeStatus, WorkerParentChildrenState, Task<OutcomeStatus>>)

WorkerBase<AdbExecuteScalarWorker<TResult>>.AddStartingCallback(Func<AdbExecuteScalarWorker<TResult>, Task<ProgressStatus>>)

WorkerBase.AddCompletedCallback(Func<WorkerBase, OutcomeStatus, Task<OutcomeStatus>>)

WorkerBase.AddRanCallback(Func<WorkerBase, OutcomeStatus, WorkerParentChildrenState, Task<OutcomeStatus>>)

WorkerBase.AddStartingCallback(Func<WorkerBase, Task<ProgressStatus>>)

WorkerBase.DefaultIsStartable()

WorkerBase.ErroredPortErrorsWorkerProtected

WorkerBase.ErrorOutputs

WorkerBase.EscalateError

WorkerBase.Inputs

WorkerBase.IsStartable

WorkerBase.Outputs

WorkerBase.Parent

WorkerBase.SucceededSequence<TLastWorker>(WorkerBase, WorkerBase, WorkerBase, WorkerBase, WorkerBase, TLastWorker)

WorkerBase.SucceededSequence<TLastWorker>(WorkerBase, WorkerBase, WorkerBase, WorkerBase, TLastWorker)

WorkerBase.SucceededSequence<TLastWorker>(WorkerBase, WorkerBase, WorkerBase, TLastWorker)

WorkerBase.SucceededSequence<TLastWorker>(WorkerBase, WorkerBase, TLastWorker)

WorkerBase.SucceededSequence<TLastWorker>(WorkerBase, TLastWorker)

WorkerBase.SucceededSequence<TLastWorker>(TLastWorker)

WorkerParent.AddChildCompletedCallback(Action<WorkerBase>)

WorkerParent.AddStartingChildrenCallback(Func<WorkerParent, Task<ProgressStatus>>)

WorkerParent.BytesPerRowBuffer

WorkerParent.Children

WorkerParent.DisposeOnFinished<TDisposable>(TDisposable)

WorkerParent.GetDownstreamFactory<TInput>()

WorkerParent.HasChildren

WorkerParent.IsCanceled

WorkerParent.IsCompleted

WorkerParent.IsCreated

WorkerParent.IsError

WorkerParent.IsFailed

WorkerParent.IsFatal

WorkerParent.IsRunning

WorkerParent.IsSucceeded

WorkerParent.KeepChildrenLevels

WorkerParent.Locator

WorkerParent.LogFactory

WorkerParent.Logger

WorkerParent.MaxRunningChildren

WorkerParent.Name

WorkerParent.RemoveChildren()

WorkerParent.RescheduleChildren()

WorkerParent.RunChildrenAsync(Boolean)

WorkerParent.RunChildrenAsync()

WorkerParent.Status

WorkerParent.Item[String]

WorkerParent.ToString()

WorkerParent.WorkerSystem

WorkerParent.DebugCommands

WorkerParent.AggregateErrorOutputRows

WorkerParent.AggregateOutputRows

WorkerParent.AggregateWorkersCompleted

WorkerParent.InstantCompleted

WorkerParent.InstantCreated

WorkerParent.InstantStarted

WorkerParent.RunningDuration

Namespace: actionETL.Adb

Assembly: actionETL.dll

Syntax

public class AdbExecuteScalarWorker<TResult> : WorkerBase<AdbExecuteScalarWorker<TResult>>, IDisposeOnFinished

Type Parameters

Name	Description
TResult	The type of the result value.

Constructors

AdbExecuteScalarWorker(WorkerParent, String, AdbCommandBuilder)

Initializes a new instance of the AdbExecuteScalarWorker<TResult> worker. It executes a query on an SQL database and returns a single result value in the ScalarResult property.

Declaration

public AdbExecuteScalarWorker(WorkerParent workerParent, string workerName, AdbCommandBuilder commandBuilder)

Parameters

Type	Name	Description
WorkerParent	workerParent	The parent worker or worker system that the new child worker will be added to. Cannot be null.
String	workerName	Name of the worker. Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1. While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1. The name cannot otherwise contain "/", and cannot start with double underscore "__".
AdbCommandBuilder	commandBuilder	A builder for the database command. Can be null, in which case CommandBuilder must be set before the worker starts running.

Exceptions

Type	Condition
ArgumentException	workerName: Workers with the same parent must have unique names. Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException	workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException	Cannot add child worker to parent which has completed. Are you adding it to the correct parent? Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

AdbExecuteScalarWorker(WorkerParent, String, IAdbConnectionBuilder, String)

Initializes a new instance of the AdbExecuteScalarWorker<TResult> worker, with CommandType set to Text. It executes a query on an SQL database and returns a single result value in the ScalarResult property.

Declaration

public AdbExecuteScalarWorker(WorkerParent workerParent, string workerName, IAdbConnectionBuilder connectionBuilder, string queryText)

Parameters

Type	Name	Description
WorkerParent	workerParent	The parent worker or worker system that the new child worker will be added to. Cannot be null.
String	workerName	Name of the worker. Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1. While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1. The name cannot otherwise contain "/", and cannot start with double underscore "__".
IAdbConnectionBuilder	connectionBuilder	The connection builder, must not be null.
String	queryText	The query text, must not be null.

Exceptions

Type	Condition
ArgumentNullException	connectionBuilder or queryText must not be null.
ArgumentException	workerName: Workers with the same parent must have unique names. Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException	workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException	Cannot add child worker to parent which has completed. Are you adding it to the correct parent? Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

AdbExecuteScalarWorker(WorkerParent, String, IAdbConnectionBuilder, String, CommandType)

Initializes a new instance of the AdbExecuteScalarWorker<TResult> worker. It executes a query on an SQL database and returns a single result value in the ScalarResult property.

Declaration

public AdbExecuteScalarWorker(WorkerParent workerParent, string workerName, IAdbConnectionBuilder connectionBuilder, string queryText, CommandType commandType)

Parameters

Type	Name	Description
WorkerParent	workerParent	The parent worker or worker system that the new child worker will be added to. Cannot be null.
String	workerName	Name of the worker. Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1. While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1. The name cannot otherwise contain "/", and cannot start with double underscore "__".
IAdbConnectionBuilder	connectionBuilder	The connection builder, must not be null.
String	queryText	The query text, must not be null.
CommandType	commandType

Exceptions

Type	Condition
ArgumentNullException	connectionBuilder or queryText must not be null. Type of the command.
ArgumentException	workerName: Workers with the same parent must have unique names. Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException	workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException	Cannot add child worker to parent which has completed. Are you adding it to the correct parent? Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

AdbExecuteScalarWorker(WorkerParent, String, Func<Boolean>, AdbCommandBuilder)

Initializes a new instance of the AdbExecuteScalarWorker<TResult> worker. It executes a query on an SQL database and returns a single result value in the ScalarResult property.

Declaration

public AdbExecuteScalarWorker(WorkerParent workerParent, string workerName, Func<bool> isStartableFunc, AdbCommandBuilder commandBuilder)

Parameters

Type	Name	Description
WorkerParent	workerParent	The parent worker or worker system that the new child worker will be added to. Cannot be null.
String	workerName	Name of the worker. Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1. While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1. The name cannot otherwise contain "/", and cannot start with double underscore "__".
Func<Boolean>	isStartableFunc	Function to calculate the worker start constraint; it should return true for startable and false for not startable. Defaults to startable if null.
AdbCommandBuilder	commandBuilder	A builder for the database command. Can be null, in which case CommandBuilder must be set before the worker starts running.

Exceptions

Type	Condition
ArgumentException	workerName: Workers with the same parent must have unique names. Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException	workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException	Cannot add child worker to parent which has completed. Are you adding it to the correct parent? Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

AdbExecuteScalarWorker(WorkerParent, String, Func<Boolean>, IAdbConnectionBuilder, String)

Initializes a new instance of the AdbExecuteScalarWorker<TResult> worker, with CommandType set to Text. It executes a query on an SQL database and returns a single result value in the ScalarResult property.

Declaration

public AdbExecuteScalarWorker(WorkerParent workerParent, string workerName, Func<bool> isStartableFunc, IAdbConnectionBuilder connectionBuilder, string queryText)

Parameters

Type	Name	Description
WorkerParent	workerParent	The parent worker or worker system that the new child worker will be added to. Cannot be null.
String	workerName	Name of the worker. Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1. While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1. The name cannot otherwise contain "/", and cannot start with double underscore "__".
Func<Boolean>	isStartableFunc	Function to calculate the worker start constraint; it should return true for startable and false for not startable. Defaults to startable if null.
IAdbConnectionBuilder	connectionBuilder	The connection builder, must not be null.
String	queryText	The query text, must not be null.

Exceptions

Type	Condition
ArgumentNullException	connectionBuilder or queryText must not be null.
ArgumentException	workerName: Workers with the same parent must have unique names. Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException	workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException	Cannot add child worker to parent which has completed. Are you adding it to the correct parent? Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

AdbExecuteScalarWorker(WorkerParent, String, Func<Boolean>, IAdbConnectionBuilder, String, CommandType)

Initializes a new instance of the AdbExecuteScalarWorker<TResult> worker. It executes a query on an SQL database and returns a single result value in the ScalarResult property.

Declaration

public AdbExecuteScalarWorker(WorkerParent workerParent, string workerName, Func<bool> isStartableFunc, IAdbConnectionBuilder connectionBuilder, string queryText, CommandType commandType)

Parameters

Type	Name	Description
WorkerParent	workerParent	The parent worker or worker system that the new child worker will be added to. Cannot be null.
String	workerName	Name of the worker. Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1. While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1. The name cannot otherwise contain "/", and cannot start with double underscore "__".
Func<Boolean>	isStartableFunc	Function to calculate the worker start constraint; it should return true for startable and false for not startable. Defaults to startable if null.
IAdbConnectionBuilder	connectionBuilder	The connection builder, must not be null.
String	queryText	The query text, must not be null.
CommandType	commandType	Type of the command.

Exceptions

Type	Condition
ArgumentNullException	connectionBuilder or queryText must not be null.
ArgumentException	workerName: Workers with the same parent must have unique names. Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException	workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException	Cannot add child worker to parent which has completed. Are you adding it to the correct parent? Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

Properties

CommandBuilder

Gets or sets the builder for the database command. Can only be set before the worker starts running.

Note: This property is thread-safe.

Declaration

public AdbCommandBuilder CommandBuilder { get; set; }

Property Value

Type	Description
AdbCommandBuilder

Exceptions

Type	Condition
InvalidOperationException	Cannot set the value after the worker has started running.

ScalarResult

Gets the result value of the query, taken from the first column of the first row of the result set. It is only available after the worker has completed successfully.

The query result (which for value types is boxed in an object) is cast to the TResult type, and if that fails it is first converted (with ChangeType(Object, Type)) and then cast. This handles e.g. the query returning a long but the worker expecting an int.

Note that some providers put a size limit on the result value, e.g. for the Microsoft.Data.SqlClient provider the limit is 2033 characters.

Note: This property is thread-safe.

Declaration

public TResult ScalarResult { get; }

Property Value

Type	Description
TResult

Exceptions

Type	Condition
InvalidOperationException	Value only available after the worker has completed successfully. Value not set.

Methods

RunAsync()

This method can be overridden to add custom functionality to the derived worker that runs before and after the row processing. In this case, the base class base.RunAsync() must be called for the worker to function correctly.

Typically, this worker is used without overriding this method.

Declaration

protected override async Task<OutcomeStatus> RunAsync()

Returns

Type	Description
Task<OutcomeStatus>	A Task describing the success or failure of the worker. An asynchronous async implementation would e.g. return OutcomeStatus.Succeeded on success, while a synchronous implementation would return OutcomeStatus.SucceededTask.

Overrides

WorkerParent.RunAsync()

Implements

IDisposeOnFinished