GET_FILESTREAM_TRANSACTION_CONTEXT (Transact-SQL)

Se aplica a:SQL Server

Devuelve un token que representa el contexto de transacción actual de una sesión. Las aplicaciones usan este token para enlazar las operaciones de transmisión por secuencias del sistema de archivos FILESTREAM a la transacción. Para obtener una lista de artículos de FILESTREAM, vea Datos de objetos grandes binarios (Blob) (SQL Server).

Convenciones de sintaxis de Transact-SQL

Sintaxis

GET_FILESTREAM_TRANSACTION_CONTEXT()

Tipos de retorno

varbinary(max)

Valor devuelto

NULL se devuelve si la transacción no se ha iniciado o se ha cancelado o confirmado.

Observaciones

La transacción debe ser explícita. Use BEGIN TRANSACTION seguido de COMMIT TRANSACTION o ROLLBACK TRANSACTION.

Cuando se llama a GET_FILESTREAM_TRANSACTION_CONTEXT, al autor de la llamada se le concede acceso al sistema de archivos a la transacción mientras dure la transacción. Para permitir que otro usuario acceda a la transacción a través del sistema de archivos, use EXECUTE AS para ejecutarse GET_FILESTREAM_TRANSACTION_CONTEXT como otro usuario.

Ejemplos

En el ejemplo siguiente se usa GET_FILESTREAM_TRANSACTION_CONTEXT en una transacción Transact-SQL para obtener el contexto de transacción.

C#

using System;
using System.Data.SqlClient;
using System.Data;

namespace ConsoleApplication
{
    /// <summary>
    /// This class is a wrapper that contains methods for:
    ///
    ///     GetTransactionContext() - Returns the current transaction context.
    ///     BeginTransaction() - Begins a transaction.
    ///     CommitTransaction() - Commits the current transaction.
    ///
    /// </summary>

    class SqlAccessWrapper
    {
        /// <summary>
        /// Returns a byte array that contains the current transaction
        /// context.
        /// </summary>
        /// <param name="sqlConnection">
        /// SqlConnection object that represents the instance of SQL Server
        /// from which to obtain the transaction context.
        /// </param>
        /// <returns>
        /// If there is a current transaction context, the return
        /// value is an Object that represents the context.
        /// If there is not a current transaction context, the
        /// value returned is DBNull.Value.
        /// </returns>

        public Object GetTransactionContext(SqlConnection sqlConnection)
        {
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()";
            cmd.CommandType = CommandType.Text;
            cmd.Connection = sqlConnection;

            return cmd.ExecuteScalar();

        }

        /// <summary>
        /// Begins the transaction.
        /// </summary>
        /// <param name="sqlConnection">
        /// SqlConnection object that represents the server
        /// on which to run the BEGIN TRANSACTION statement.
        /// </param>

        public void BeginTransaction(SqlConnection sqlConnection)
        {
            SqlCommand cmd = new SqlCommand();

            cmd.CommandText = "BEGIN TRANSACTION";
            cmd.CommandType = CommandType.Text;
            cmd.Connection = sqlConnection;

            cmd.ExecuteNonQuery();
        }

        /// <summary>
        /// Commits the transaction.
        /// </summary>
        /// <param name="sqlConnection">
        /// SqlConnection object that represents the instance of SQL Server
        /// on which to run the COMMIT statement.
        /// </param>

        public void CommitTransaction(SqlConnection sqlConnection)
        {
            SqlCommand cmd = new SqlCommand();

            cmd.CommandText = "COMMIT TRANSACTION";
            cmd.CommandType = CommandType.Text;
            cmd.Connection = sqlConnection;

            cmd.ExecuteNonQuery();
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            //Open a connection to the local instance of SQL Server.

            SqlConnection sqlConnection = new SqlConnection("Integrated Security=true;server=(local)");
            sqlConnection.Open();

            SqlAccessWrapper sql = new SqlAccessWrapper();

            //Create a transaction so that sql.GetTransactionContext() will succeed.
            sql.BeginTransaction(sqlConnection);

            //The transaction context will be stored in this array.
            Byte[] transactionToken;

            Object txObj = sql.GetTransactionContext(sqlConnection);
            if (DBNull.Value != txObj)
            {
                transactionToken = (byte[])txObj;
                Console.WriteLine("Transaction context obtained.\n");
            }

            sql.CommitTransaction(sqlConnection);
        }
    }
}

Visual Basic .NET

Imports System
Imports System.Data.SqlClient
Imports System.Data

Namespace ConsoleApplication
    ''' <summary>
    ''' This class is a wrapper that contains methods for:
    '''
    ''' GetTransactionContext() - Returns the current transaction context.
    ''' BeginTransaction() - Begins a transaction.
    ''' CommitTransaction() - Commits the current transaction.
    '''
    ''' </summary>

    Class SqlAccessWrapper
        ''' <summary>
        ''' Returns a byte array that contains the current transaction
        ''' context.
        ''' </summary>
        ''' <param name="sqlConnection">
        ''' SqlConnection object that represents the instance of SQL Server
        ''' from which to obtain the transaction context.
        ''' </param>
        ''' <returns>
        ''' If there is a current transaction context, the return
        ''' value is an Object that represents the context.
        ''' If there is not a current transaction context, the
        ''' value returned is DBNull.Value.
        ''' </returns>

        Public Function GetTransactionContext(ByVal sqlConnection As SqlConnection) As Object
            Dim cmd As New SqlCommand()
            cmd.CommandText = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()"
            cmd.CommandType = CommandType.Text
            cmd.Connection = sqlConnection

            Return cmd.ExecuteScalar()

        End Function

        ''' <summary>
        ''' Begins the transaction.
        ''' </summary>
        ''' <param name="sqlConnection">
        ''' SqlConnection object that represents the server
        ''' on which to run the BEGIN TRANSACTION statement.
        ''' </param>

        Public Sub BeginTransaction(ByVal sqlConnection As SqlConnection)
            Dim cmd As New SqlCommand()

            cmd.CommandText = "BEGIN TRANSACTION"
            cmd.CommandType = CommandType.Text
            cmd.Connection = sqlConnection

            cmd.ExecuteNonQuery()
        End Sub

        ''' <summary>
        ''' Commits the transaction.
        ''' </summary>
        ''' <param name="sqlConnection">
        ''' SqlConnection object that represents the instance of SQL Server
        ''' on which to run the COMMIT statement.
        ''' </param>

        Public Sub CommitTransaction(ByVal sqlConnection As SqlConnection)
            Dim cmd As New SqlCommand()

            cmd.CommandText = "COMMIT TRANSACTION"
            cmd.CommandType = CommandType.Text
            cmd.Connection = sqlConnection

            cmd.ExecuteNonQuery()
        End Sub
    End Class

    Class Program
        Shared Sub Main()
            '''Open a connection to the local instance of SQL Server.

            Dim sqlConnection As New SqlConnection("Integrated Security=true;server=(local)")
            sqlConnection.Open()

            Dim sql As New SqlAccessWrapper()

            '''Create a transaction so that sql.GetTransactionContext() will succeed.
            sql.BeginTransaction(sqlConnection)

            '''The transaction context will be stored in this array.
            Dim transactionToken As Byte()

            Dim txObj As Object = sql.GetTransactionContext(sqlConnection)

            '''If the returned object is not NULL, there is a valid transaction
            '''token, and it must be converted into a format that is usable within
            '''the application.

            If Not txObj.Equals(DBNull.Value) Then
                transactionToken = DirectCast(txObj, Byte())
                Console.WriteLine("Transaction context obtained." & Chr(10) & "")
            End If

            sql.CommitTransaction(sqlConnection)
        End Sub
    End Class
End Namespace

Contenido relacionado

• PathName (Transact-SQL)
• Datos de objeto binario grande (Blob) (SQL Server)