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 temas sobre FILESTREAM, consulte Datos de objeto binario grande (Blob) (SQL Server).

Convenciones de sintaxis de Transact-SQL

Sintaxis

  
GET_FILESTREAM_TRANSACTION_CONTEXT ()  

Tipo de valor devuelto

varbinary(max)

Valor devuelto

Se devuelve NULL si no se ha iniciado la transacción o si 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, el autor de la llamada obtiene acceso a la transacción a través del sistema de archivos mientras dure la transacción. Para que otro usuario pueda tener acceso a la transacción a través del sistema de archivos, use EXECUTE AS para ejecutar GET_FILESTREAM_TRANSACTION_CONTEXT como el otro usuario.

Ejemplos

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

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);  
        }  
    }  
}  

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  

Consulte también

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