Question

我正在尝试为流文件实现ihttphandeler。文件可能是微小的缩略图或巨大的电影二进制文件r存储在sql server中我在网上看了很多代码，但有些东西没有意义是不是流媒体应该逐个读取数据并将其移动到线上？大多数代码似乎首先从mssql到内存读取整个字段，然后使用流式输出写入
实际上从磁盘直接流到http的字节（或缓冲的块？）是不是更有效率继承了我的代码到目前为止，但无法找出sqlreader模式与流对象和书写系统的正确组合

Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
     context.Response.BufferOutput = False
    Dim FileField=safeparam(context.Request.QueryString("FileField"))
     Dim FileTable=safeparam(context.Request.QueryString("FileTable"))
     Dim KeyField=safeparam(context.Request.QueryString("KeyField"))
     Dim FileKey=safeparam(context.Request.QueryString("FileKey"))                 
    Using connection As New SqlConnection(ConfigurationManager.ConnectionStrings("Main").ConnectionString)
        Using command As New SqlCommand("SELECT " & FileField & "Bytes," & FileField & "Type FROM " & FileTable & " WHERE " & KeyField & "=" & FileKey, connection)
            command.CommandType = Data.CommandType.Text

结束使用结束使用结束子

请注意，此sql命令还会在查询的第二个字段中返回文件扩展名（pdf，jpg，doc ...）

非常感谢你

编辑：

我设法找到了更多代码，现在页面间歇性地出现了。有时它带来pdf文件，有时它不会我无法理解这里的模式我认为主要问题是当请求来自不同的页面并且我点击“在新标签中显示”然后它从未起作用。当我做“在新窗口中显示”时，它主要起作用但并非总是如此顺便说一句。代码总是运行。从不打破或错误或类似的东西。每次请求时，它都像一个好孩子一样从头到尾运行有时IE很长一段时间后，给我一条消息（来自新标签）“Adobe / Acrobat阅读器有问题。请退出Adobe Acrobat / Reader再试一次。”
问题是什么？
继承我当前的代码

Shared Sub ProccessMedia(ByVal context As HttpContext)
    If CurPerson Is Nothing OrElse Not CurPerson.PersonExts.FirstOrDefault.LetAllFiles Then Exit Sub
    context.Response.BufferOutput = False
    Dim FileField = SafeParam(context.Request.QueryString("FileField"))
    Dim FileTable = SafeParam(context.Request.QueryString("FileTable"))
    Dim KeyField = SafeParam(context.Request.QueryString("KeyField"))
    Dim FileKey = SafeParam(context.Request.QueryString("FileKey"))
    Dim oSqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("Main").ConnectionString)
    Dim oSqlCommand = New SqlCommand("SELECT " & FileField & "Type," & FileField & "Bytes FROM " & FileTable & " WHERE " & KeyField & "=" & FileKey, oSqlConnection)
    oSqlConnection.Open()
    Dim oSqlDataReader = oSqlCommand.ExecuteReader(CommandBehavior.SequentialAccess)
    If oSqlDataReader.Read() Then
        context.Response.ContentType = GetMIMEType(oSqlDataReader.GetString(0))
        Dim bufferSize = 8040
        Dim chunk = New Byte(bufferSize - 1) {}
        Dim retCount As Long
        Dim startIndex As Long = 0
        retCount = oSqlDataReader.GetBytes(1, startIndex, chunk, 0, bufferSize)
        While retCount = bufferSize
            context.Response.BinaryWrite(chunk)
            startIndex += bufferSize
            retCount = oSqlDataReader.GetBytes(1, startIndex, chunk, 0, bufferSize)
        End While
        oSqlDataReader.Close()
        oSqlConnection.Close()
        Dim actualChunk = New Byte(retCount - 2) {}
        Buffer.BlockCopy(chunk, 0, actualChunk, 0, CInt(retCount) - 1)
        context.Response.BinaryWrite(actualChunk)
    End If
End Sub

非常感谢

Answer 1

间歇性已经停止。不知道为什么。

但现在工作正常

.net IHTTPHandler流式SQL二进制数据

1 个答案: