我如何确定在.NET中的文件的内容类型？ [英] How do I determine a file's content type in .NET?

问题描述

我的WPF应用程序从用户获取一个文件Microsoft.Win32.OpenFileDialog（）...

My WPF application gets a file from the user with Microsoft.Win32.OpenFileDialog()...

Private Sub ButtonUpload_Click(...)
    Dim FileOpenStream As Stream = Nothing
    Dim FileBox As New Microsoft.Win32.OpenFileDialog()
    FileBox.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
    FileBox.Filter = "Pictures (*.jpg;*.jpeg;*.gif;*.png)|*.jpg;*.jpeg;*.gif;*.png|" & _
                     "Documents (*.pdf;*.doc;*.docx;)|*.pdf;*.doc;*.docx;|" & _
                     "All Files (*.*)|*.*"
    FileBox.FilterIndex = 1
    FileBox.Multiselect = False
    Dim FileSelected As Nullable(Of Boolean) = FileBox.ShowDialog(Me)
    If FileSelected IsNot Nothing AndAlso FileSelected.Value = True Then
        Try
            FileOpenStream = FileBox.OpenFile()
            If (FileOpenStream IsNot Nothing) Then
                Dim ByteArray As Byte()
                Using br As New BinaryReader(FileOpenStream)
                    ByteArray = br.ReadBytes(FileOpenStream.Length)
                End Using
                Dim z As New ZackFile
                z.Id = Guid.NewGuid
                z.FileData = ByteArray
                z.FileSize = CInt(ByteArray.Length)
                z.FileName = FileBox.FileName.Split("\").Last
                z.DateAdded = Now
                db.AddToZackFile(z)
                db.SaveChanges()
            End If
        Catch Ex As Exception
            MessageBox.Show("Cannot read file from disk. " & Ex.Message, "Fail", MessageBoxButton.OK, MessageBoxImage.Error)
        Finally
            If (FileOpenStream IsNot Nothing) Then
                FileOpenStream.Close()
            End If
        End Try
    End If
End Sub

和我的ASP.NET MVC应用程序在一个网站FileStreamResult（）

And my ASP.NET MVC application serves it up for download at a web site with FileStreamResult()...

Public Class ZackFileController
    Inherits System.Web.Mvc.Controller

    Function Display(ByVal id As Guid) As FileStreamResult
        Dim db As New EfrDotOrgEntities
        Dim Model As ZackFile = (From z As ZackFile In db.ZackFile _
                                Where z.Id = id _
                                Select z).First
        Dim ByteArray As Byte() = Model.ImageData
        Dim FileStream As System.IO.MemoryStream = New System.IO.MemoryStream(ByteArray)
        Dim ContentType As String = ?????
        Dim f As New FileStreamResult(FileStream, ContentType)
        f.FileDownloadName = Model.FileName
        Return f
    End Function

End Class

但FileStreamResult（）需要一个内容类型的字符串。我怎么知道我的文件的正确内容类型？

But FileStreamResult() needs a content type string. How do I know the correct content type of my file?

推荐答案

我已经取代了FileExtension列在我的数据库表contentType都列。

I've replaced the FileExtension column in my database table with a ContentType column.

我来填充它，当我上传的文件。

I populate it when I upload a file.

Private Sub ButtonUpload_Click(...)
    ...
    Dim FileExtension As String = "." + FileBox.FileName.Split(".").Last.ToLower
    z.ContentType = ContentType(FileExtension)
    ...
End Sub

我决定使用此功能的内容类型：

I determine the content type with this function:

Function ContentType(ByVal FileExtension As String) As String
    Dim d As New Dictionary(Of String, String)
    'Images'
    d.Add(".bmp", "image/bmp")
    d.Add(".gif", "image/gif")
    d.Add(".jpeg", "image/jpeg")
    d.Add(".jpg", "image/jpeg")
    d.Add(".png", "image/png")
    d.Add(".tif", "image/tiff")
    d.Add(".tiff", "image/tiff")
    'Documents'
    d.Add(".doc", "application/msword")
    d.Add(".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document")
    d.Add(".pdf", "application/pdf")
    'Slideshows'
    d.Add(".ppt", "application/vnd.ms-powerpoint")
    d.Add(".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation")
    'Data'
    d.Add(".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
    d.Add(".xls", "application/vnd.ms-excel")
    d.Add(".csv", "text/csv")
    d.Add(".xml", "text/xml")
    d.Add(".txt", "text/plain")
    'Compressed Folders'
    d.Add(".zip", "application/zip")
    'Audio'
    d.Add(".ogg", "application/ogg")
    d.Add(".mp3", "audio/mpeg")
    d.Add(".wma", "audio/x-ms-wma")
    d.Add(".wav", "audio/x-wav")
    'Video'
    d.Add(".wmv", "audio/x-ms-wmv")
    d.Add(".swf", "application/x-shockwave-flash")
    d.Add(".avi", "video/avi")
    d.Add(".mp4", "video/mp4")
    d.Add(".mpeg", "video/mpeg")
    d.Add(".mpg", "video/mpeg")
    d.Add(".qt", "video/quicktime")
    Return d(FileExtension)
End Function

这工作，但它看起来不太优雅。

This works, but it seems inelegant.

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