GET_FILESTREAM_TRANSACTION_CONTEXT (Transact-SQL)
Gibt ein Token zurück, das den aktuellen Transaktionskontext einer Sitzung darstellt. Eine Anwendung verwendet dieses Token, um FILESTREAM-Dateisystem-Streamingvorgänge an die Transaktion zu binden. Eine Liste der FILESTREAM-Themen finden Sie unter Binary Large Object (BLOB)-Daten (SQL Server).
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Transact-SQL-Syntaxkonventionen
Syntax
GET_FILESTREAM_TRANSACTION_CONTEXT ()
Rückgabetyp
varbinary(max)
Rückgabewert
NULL wird zurückgegeben, wenn die Transaktion nicht gestartet wurde, wenn sie abgebrochen wurde oder wenn ein Commit durchgeführt wurde.
Hinweise
Die Transaktion muss explizit sein. Verwenden Sie BEGIN TRANSACTION gefolgt von COMMIT TRANSACTION oder ROLLBACK TRANSACTION.
Wenn Sie GET_FILESTREAM_TRANSACTION_CONTEXT aufrufen, wird dem Aufrufer für die Dauer der Transaktion Zugriff auf das Dateisystem für die Transaktion gewährt. Um einem anderen Benutzer den Zugriff auf die Transaktion über das Dateisystem zu ermöglichen, verwenden Sie EXECUTE AS, um GET_FILESTREAM_TRANSACTION_CONTEXT als dieser andere Benzutzer auszuführen.
Beispiele
Im folgenden Beispiel wird GET_FILESTREAM_TRANSACTION_CONTEXT in einer Transact-SQL-Transaktion verwendet, um den Transaktionskontext zu erhalten.
using System;
using System.Data.SqlClient;
using System.Data;
namespace ConsoleApplication
{
/// <summary>
/// This class is a wrapper that contains methods for:
///
/// GetTransactionContect() - Returns the current transaction context.
/// BeginTransaction() - Begins a transaction.
/// CommmitTransaction() - 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:
'''
''' GetTransactionContect() - Returns the current transaction context.
''' BeginTransaction() - Begins a transaction.
''' CommmitTransaction() - 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