带进度的SQLServerFileStream如何存取

 -- =========================================================-- 启用 filestream_access_level-- =========================================================EXEC sp_configure 'filestream_access_level', 2; -- 0=禁用 1=针对 T-SQL 访问启用 FILESTREAM 2=针对 T-SQL 和 WIN32 流访问启用 FILESTREAMRECONFIGURE;
GO-- =========================================================-- 创建测试数据库-- =========================================================EXEC master..xp_create_subdir 'f:\temp\db\_test';CREATE DATABASE _testON
 PRIMARY(
 NAME = _test, FILENAME = 'f:\temp\db\_test\_test.mdf'),
 FILEGROUP FG_stream CONTAINS FILESTREAM(
 NAME = _test_file_stream, FILENAME = 'f:\temp\db\_test\stream')
 LOG ON(
 NAME = _test_log, FILENAME = 'f:\temp\db\_test\_test.ldf')
;GO-- =========================================================-- FileStream-- =========================================================-- =================================================-- 创建 包含 FileStream 数据的表-- -------------------------------------------------CREATE TABLE _test.dbo.tb_fs(
 id uniqueidentifier ROWGUIDCOL -- 必需 DEFAULT NEWSEQUENTIALID ( ) PRIMARY KEY,
 name nvarchar(260),
 content varbinary(max) FILESTREAM
);GO

下面的 VB 脚本实现带进度显示的文件存(Write方法）取（Read方法）

Imports System.IO
Imports System
Imports System.Collections.Generic
Imports System.Text
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Module Module1
 Public Sub Main(ByVal args As String())
 Dim sqlConnection As New SqlConnection("Integrated Security=true;server=localhost")
 Try
 sqlConnection.Open()
 Console.WriteLine("将文件保存到 FileStream")
 Write(sqlConnection, "test", "f:\temp\re.csv")
 Console.WriteLine("从 FileStream 读取数据保存到文件")
 Read(sqlConnection, "test", "f:\temp\re_1.csv")
 Catch ex As System.Exception
 Console.WriteLine(ex.ToString())
 Finally
 sqlConnection.Close() End Try
 Console.WriteLine("处理结束，按 Enter 退出")
 Console.ReadLine() End Sub ''' <summary>
 ''' 将文件保存到数据库 ''' </summary>
 ''' <param name="conn">数据库连接</param> ''' <param name="name">名称</param>
 ''' <param name="file">文件名</param>
 Sub Write(ByVal conn As SqlConnection, ByVal name As String, ByVal file As String)
 Dim bufferSize As Int32 = 1024
 Using sqlCmd As New SqlCommand
 sqlCmd.Connection = conn '事务
 Dim transaction As SqlTransaction = conn.BeginTransaction("mainTranaction")
 sqlCmd.Transaction = transaction
 '1. 读取 FILESTREAM 文件路径 ( 注意函数大小写 )
 sqlCmd.CommandText = "
UPDATE _test.dbo.tb_fs SET content = 0x WHERE name = @name;
IF @@ROWCOUNT = 0 INSERT _test.dbo.tb_fs(name, content) VALUES( @name, 0x );
SELECT content.PathName() FROM _test.dbo.tb_fs WHERE name = @name;"
 sqlCmd.Parameters.Add(New SqlParameter("name", name))
 Dim filePath As String = Nothing
 Dim pathObj As Object = sqlCmd.ExecuteScalar() If Not pathObj.Equals(DBNull.Value) Then
 filePath = DirectCast(pathObj, String) Else
 Throw New System.Exception("content.PathName() failed to read the path name for the content column.") End If
 '2. 读取当前事务上下文
 sqlCmd.CommandText = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()"
 Dim obj As Object = sqlCmd.ExecuteScalar()
 Dim txContext As Byte() = Nothing
 Dim contextLength As UInteger
 If Not obj.Equals(DBNull.Value) Then
 txContext = DirectCast(obj, Byte())
 contextLength = txContext.Length()
 Else
 Dim message As String = "GET_FILESTREAM_TRANSACTION_CONTEXT() failed"
 Throw New System.Exception(message)
 End If
 '3. 获取 Win32 句柄，并使用该句柄在 FILESTREAM BLOB 中读取和写入数据 Using sqlFileStream As New SqlFileStream(filePath, txContext, FileAccess.Write)
 Dim buffer As Byte() = New Byte(bufferSize - 1) {}
 Dim numBytes As Integer = 0
 Using fsRead As New FileStream(file, FileMode.Open)
 While True
 numBytes = fsRead.Read(buffer, 0, bufferSize) If numBytes = 0 Then Exit While
 sqlFileStream.Write(buffer, 0, numBytes)
 Console.WriteLine(String.Format("{0} -> {1} -> {2}", fsRead.Position, sqlFileStream.Position, numBytes)) End While
 fsRead.Close() End Using
 sqlFileStream.Close() End Using
 sqlCmd.Transaction.Commit() End Using
 End Sub ''' <summary>
 ''' 从数据库读取数据保存到文件 ''' </summary>
 ''' <param name="conn">数据库连接</param> ''' <param name="name">名称</param>
 ''' <param name="file">文件名</param>
 Sub Read(ByVal conn As SqlConnection, ByVal name As String, ByVal file As String)
 Dim bufferSize As Int32 = 1024
 Using sqlCmd As New SqlCommand
 sqlCmd.Connection = conn '1. 读取 FILESTREAM 文件路径 ( 注意函数大小写 )
 sqlCmd.CommandText = "SELECT content.PathName() FROM _test.dbo.tb_fs WHERE name = @name;"
 sqlCmd.Parameters.Add(New SqlParameter("name", name))
 Dim filePath As String = Nothing
 Dim pathObj As Object = sqlCmd.ExecuteScalar()
 If Not pathObj.Equals(DBNull.Value) Then
 filePath = DirectCast(pathObj, String)
 Else
 Throw New System.Exception("content.PathName() failed to read the path name for the content column.")
 End If
 '2. 读取当前事务上下文
 Dim transaction As SqlTransaction = conn.BeginTransaction("mainTranaction")
 sqlCmd.Transaction = transaction
 sqlCmd.CommandText = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()"
 Dim obj As Object = sqlCmd.ExecuteScalar()
 Dim txContext As Byte() = Nothing
 Dim contextLength As UInteger If Not obj.Equals(DBNull.Value) Then
 txContext = DirectCast(obj, Byte())
 contextLength = txContext.Length() Else
 Dim message As String = "GET_FILESTREAM_TRANSACTION_CONTEXT() failed"
 Throw New System.Exception(message) End If
 '3. 获取 Win32 句柄，并使用该句柄在 FILESTREAM BLOB 中读取和写入数据
 Using sqlFileStream As New SqlFileStream(filePath, txContext, FileAccess.Read)
 Dim buffer As Byte() = New Byte(bufferSize - 1) {}
 Dim numBytes As Integer = 0
 Using fsRead As New FileStream(file, FileMode.Create)
 While True
 numBytes = sqlFileStream.Read(buffer, 0, bufferSize)
 If numBytes = 0 Then Exit While
 fsRead.Write(buffer, 0, numBytes)
 Console.WriteLine(String.Format("{0} -> {1} -> {2}", sqlFileStream.Position, sqlFileStream.Position, numBytes))
 End While
 fsRead.Close()
 End Using
 sqlFileStream.Close()
 End Using
 sqlCmd.Transaction.Commit()
 End Using
 End Sub
End Module

本文讲解了带进度的SQL Server FileStream如何存取 ，更多相关内容请关注Gxl网。

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