带进度的SQL Server FileStream如何存取

SQL Server FileStream 功能的详细参考联机帮助设计和实现 FILESTREAM 存储
这里只是把使用 Win32 管理 FILESTREAM 数据的代码调整了一下，实现带进度的存取，这对于存取较大的文件比较有意义
   要使用FileStream，首先要在 SQL Server配置管理器中打开FileStream选项：SQL Server配置管理器–SQL Server服务–右边的服务列表中找到SQL Server服务–属性–FILESTREAM–允许远程客户端访问FILESTREAM数据根据需要选择，其他两荐都选上。配置完成后，需要重新启动SQL Server服务使设置生效。
   然后使用下面的脚本创建测试数据库和测试表

 -- =========================================================-- 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    &#39;&#39;&#39; <summary>
    &#39;&#39;&#39; 将文件保存到数据库    &#39;&#39;&#39; </summary>
    &#39;&#39;&#39; <param name="conn">数据库连接</param>    &#39;&#39;&#39; <param name="name">名称</param>
    &#39;&#39;&#39; <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            &#39;事务
            Dim transaction As SqlTransaction = conn.BeginTransaction("mainTranaction")
            sqlCmd.Transaction = transaction
            &#39;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
            &#39;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
            &#39;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    &#39;&#39;&#39; <summary>
    &#39;&#39;&#39; 从数据库读取数据保存到文件    &#39;&#39;&#39; </summary>
    &#39;&#39;&#39; <param name="conn">数据库连接</param>    &#39;&#39;&#39; <param name="name">名称</param>
    &#39;&#39;&#39; <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            &#39;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
            &#39;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
            &#39;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

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