GET_FILESTREAM_TRANSACTION_CONTEXT (Transact-SQL)
セッションの現在のトランザクション コンテキストを表すトークンを返します。アプリケーションでは、このトークンを使用して、FILESTREAM のファイル システム ストリーミング操作をトランザクションにバインドします。FILESTREAM に関するトピックの一覧については、「FILESTREAM ストレージの設計と実装」を参照してください。
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構文
GET_FILESTREAM_TRANSACTION_CONTEXT ()
戻り値の型
varbinary(max)
戻り値
トランザクションが開始されていないか、キャンセルまたはコミットされている場合、NULL が返されます。
説明
トランザクションは明示的にする必要があります。BEGIN TRANSACTION に続けて、COMMIT TRANSACTION または ROLLBACK TRANSACTION を使用します。
GET_FILESTREAM_TRANSACTION_CONTEXT を呼び出すと、トランザクションへのファイル システム アクセス権が呼び出し元に与えられます。このアクセス権は、トランザクションが完了するまで有効です。トランザクションに対するファイル システム経由のアクセスを別のユーザーに許可するには、EXECUTE AS を使用して、別のユーザーとして GET_FILESTREAM_TRANSACTION_CONTEXT を実行します。
例
次の例では、GET_FILESTREAM_TRANSACTION_CONTEXT を Transact-SQL トランザクションで使用して、トランザクション コンテキストを取得します。
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