怎么会报错？晕了。在线等待

[tommerxx]

我参照孟子E章提供的http://xml.sz.luohuedu.net/xml/ShowDetail.asp?id=2A5DD7C6-A45A-48AB-A2E8-342A29F17506编写如下代码：

Dim intImageSize As Int64
Dim strImageType As String
Dim ImageStream As Stream
' 获得图片的大小
intImageSize = photos.PostedFile.ContentLength
' 获得图片类型
strImageType = photos.PostedFile.ContentType
'读取图片
ImageStream = PersonImage.PostedFile.InputStream
Dim ImageContent(intImageSize) As Byte
Dim intStatus As Integer
intStatus = ImageStream.Read(ImageContent, 0, intImageSize)

Dim photoConn As New SqlConnection()
photoConn.ConnectionString = "Data Source=Localhost; Initial Catalog=userinfo; user id=sa; password=sa;"
photoConn.Open()

Dim myCommand As New SqlCommand("photo", photoConn)
myCommand.CommandType = CommandType.StoredProcedure

Dim thephotos As New SqlParameter("@photos", SqlDbType.Image)
thephotos.Value = ImageContent
myCommand.Parameters.Add(thephotos)

Dim thephototype As New SqlParameter("@phototype", SqlDbType.VarChar, 255)
thephototype.Value = strImageType
myCommand.Parameters.Add(thephototype)

Try
myCommand.ExecuteNonQuery()
Response.Redirect("myclassphoto.aspx?classid=" & Request("classid"))
Catch SQLexc As SqlException
Response.Write("添加失败，原因：" & SQLexc.ToString())
End Try

photoConn.Close()

运行时报错：

未将对象引用设置到对象的实例。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。

源错误:


行 284： Dim ImageStream As Stream
行 285： ' 获得图片的大小
行 286： intImageSize = photos.PostedFile.ContentLength （此行红色）
行 287： ' 获得图片类型
行 288： strImageType = photos.PostedFile.ContentType

堆栈跟踪:


[NullReferenceException: 未将对象引用设置到对象的实例。]
myguestbook.myclassdetail.Button2_ServerClick(Object sender, EventArgs e) in D:\myguestbook\myguestbook\myclasswords.aspx.vb:286
System.Web.UI.HtmlControls.HtmlButton.OnServerClick(EventArgs e) +108
System.Web.UI.HtmlControls.HtmlButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +57
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +18
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +138
System.Web.UI.Page.ProcessRequestMain() +1263

这是什么原因？望各位高手予以指点。

[coldice]

你必须的在aspx页面中定义一个ID为photos的上传文件组件

[wolve]

If Not Me.Request.Files.Count > 0 Then
Return
End If


Dim file As HttpPostedFile = Me.Request.Files(0)
If file Is Nothing Or file.ContentLength > FileManager.MAX_FILE_LENGTH Then
Return
End If
Dim buffer(FileManager.MAX_FILE_LENGTH) As Byte
file.InputStream.Read(buffer, 0, buffer.Length)
Dim conn As SqlClient.SqlConnection = ConnectionFactory.GetConnection()
Dim name() As String = file.FileName.Split("\")
conn.Open()
FileManager.SaveFileToDB(conn, buffer, file.ContentType, TextBox1.Text, TextBox2.Text)
conn.Dispose()
file = Nothing
buffer = Nothing

先判断一下有没有上传文件。

[saucer]

<form runat=server enctype="multipart/form-data">
<input type="file" id="photos" runat=server />
...