Class DuckDbCommand

ADO.NET-compatible command object to execute a query/statement against a DuckDB database.

Inheritance

object

DuckDbCommand

Implements

IDbCommand

IDisposable

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: Mallard.Ado

Assembly: Mallard.dll

Syntax

public sealed class DuckDbCommand : IDbCommand, IDisposable

Remarks

An instance of this class should only be used from one thread at a time. While multi-thread access will not cause memory/.NET runtime corruption, the object may misbehave or throw exceptions due to inconsistent internal state.

Properties

CommandText

The SQL query or statement(s) to execute.

Declaration

public string CommandText { get; set; }

Property Value

Type	Description
string	The query or statement(s) in DuckDB's SQL dialect. Multiple statements may be separated/terminated by semicolons; the results returned are always from the last statement.

Remarks

The default value is the empty string. This property must be changed to get a valid command. Setting this property will invalidate any preparation for the previously-set statement(s).

Connection

The connection that this command works on.

Declaration

public DuckDbConnection Connection { get; }

Property Value

Type	Description
DuckDbConnection

Parameters

The parameters that should be applied to a parameterized SQL query or statement.

Declaration

public DuckDbParameterCollection Parameters { get; }

Property Value

Type	Description
DuckDbParameterCollection

UpdatedRowSource

Gets or sets how command results are applied to the DataRow when used by the Update(DataSet) method of a DbDataAdapter.

Declaration

public UpdateRowSource UpdatedRowSource { get; set; }

Property Value

Type	Description
UpdateRowSource	One of the UpdateRowSource values. The default is Both unless the command is automatically generated. Then the default is None.

Exceptions

Type	Condition
ArgumentException	The value entered was not one of the UpdateRowSource values.

Methods

Cancel()

Attempt to cancel the executing query or statement (invoked by a different thread).

Declaration

public void Cancel()

Remarks

This method is supposed to implement Cancel(), although its semantics are subtly different from the specification. Cancel() is supposed to cancel the specific command represented by its receiver. However, DuckDB's native API does not allow cancelling specific commands, but only the currently executing command on the database connection as a whole; see Interrupt(). This method can only be implemented in the same way. That is, this method might cancel the wrong command, that is not the method's receiver argument.

Since the same DuckDB connection cannot run multiple queries at the same time from different threads (execution is always serialized), the divergence of what this method does from the specification means little in practice: there should be only one "active" command per connection anyway.

Exceptions

Type	Condition
ObjectDisposedException	The connection has already been disposed (closed).

CreateParameter()

Creates a new instance of an IDbDataParameter object.

Declaration

public IDbDataParameter CreateParameter()

Returns

Type	Description
IDbDataParameter	An IDbDataParameter object.

Dispose()

Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

Declaration

public void Dispose()

ExecuteNonQuery()

Executes an SQL statement against the Connection object of a .NET data provider, and returns the number of rows affected.

Declaration

public int ExecuteNonQuery()

Returns

Type	Description
int	The number of rows affected.

Exceptions

Type	Condition
InvalidOperationException	The connection does not exist. -or- The connection is not open.

ExecuteReader()

Executes the CommandText against the Connection and builds an IDataReader.

Declaration

public DuckDbDataReader ExecuteReader()

Returns

Type	Description
DuckDbDataReader	An IDataReader object.

ExecuteReader(CommandBehavior)

Executes the CommandText against the Connection, and builds an IDataReader using one of the CommandBehavior values.

Declaration

public IDataReader ExecuteReader(CommandBehavior behavior)

Parameters

Type	Name	Description
CommandBehavior	behavior	One of the CommandBehavior values.

Returns

Type	Description
IDataReader	An IDataReader object.

ExecuteScalar()

Executes the query, and returns the first column of the first row in the resultset returned by the query. Extra columns or rows are ignored.

Declaration

public object? ExecuteScalar()

Returns

Type	Description
object	The first column of the first row in the resultset.

Prepare()

Prepare the SQL statement for execution.

Declaration

public void Prepare()

Remarks

In DuckDB, in a sense, all statements must be prepared whether they use parameters or not. The statement set in CommandText will be implicitly prepared even without this calling this method.

Thus calling this method does not save any computational work. However, it may still be useful to call it to check for errors in the SQL statement before proceeding to set values for the parameters.

Exceptions

Type	Condition
ObjectDisposedException	The connection has already been disposed (closed).
DuckDbException	There is an error in preparing the statement, e.g. from a syntax error.

Implements

IDbCommand

IDisposable