Question

这是我的问题。我有一个用户控件，它将使用gridview中的链接按钮下载二进制文件（图像，pdf等）。

<asp:GridView Visible="true" ID="GridView1" runat="server" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
RowStyle-BackColor="#A1DCF2" AlternatingRowStyle-BackColor="White" AlternatingRowStyle-ForeColor="#000"
AutoGenerateColumns="false">
<Columns>
            <asp:BoundField DataField="ID" HeaderText="ID"/>
    <asp:BoundField DataField="FileName" HeaderText="File Name"/>
    <asp:TemplateField HeaderText="Action" ItemStyle-HorizontalAlign = "Center">
        <ItemTemplate>
         <asp:LinkButton ID="lnkDownload" runat="server" Text="Download" OnClick="DownloadFile" CommandArgument='<%# Eval("Id") %>'></asp:LinkButton>
         <asp:LinkButton ID="lnkDelete" runat="server" Text="Delete" OnClick="DeleteFile"  CommandArgument='<%# Eval("Id") %>'></asp:LinkButton>
        </ItemTemplate>
    </asp:TemplateField>
</Columns>
</asp:GridView>

代码背后：

Protected Sub DownloadFile(sender As Object, e As EventArgs)
    Dim id As Integer = Integer.Parse(TryCast(sender, LinkButton).CommandArgument)
    Dim bytes As Byte()
    Dim fileName As String, contentType As String

    Using con As New SqlConnection(DataSource.ConnectionString)
        Using cmd As New SqlCommand()
            cmd.CommandText = "select FileName, PatImage, FileType from DB where Id=@Id"
            cmd.Parameters.AddWithValue("@Id", id)
            cmd.Connection = con
            con.Open()
            Using sdr As SqlDataReader = cmd.ExecuteReader()
                sdr.Read()
                bytes = DirectCast(sdr("PatImage"), Byte())
                contentType = sdr("FileType").ToString()
                fileName = sdr("FileName").ToString()
            End Using
            con.Close()
        End Using
    End Using
    Response.Clear()
    Response.Buffer = True
    Response.Charset = ""
    Response.Cache.SetCacheability(HttpCacheability.NoCache)
    Response.ContentType = contentType
    Response.AppendHeader("Content-Disposition", "attachment; filename=" + fileName)
    Response.BinaryWrite(bytes)
    Response.Flush()
    Response.End()
End Sub

但如果我的父aspx页面中有UpdatePanel，则无效。所以我用Google搜索，我找到了答案;那就是在RowDataBound中放置代码：

Private Sub GridView1_RowDataBound(sender As Object, e As GridViewRowEventArgs) Handles GridView1.RowDataBound
    Dim lb As LinkButton = TryCast(e.Row.FindControl("lnkDownload"), LinkButton )
    ScriptManager.GetCurrent(Me.Page).RegisterAsyncPostBackControl(lb)
End Sub

发生了新的错误。那就是我在我的GridView中使用我的RowDataBound中的代码找不到我的linkButton。

所以我再次搜索，我发现我应该在我的aspx页面ClientIDMode="AutoID"中添加一个属性。但这仅适用于框架4.x.我不能这样做因为我目前正在使用3.5。在我目前的情况下是否有任何补救措施？

Answer 1

已经找到答案，我刚刚更改了我的RowDataBound内容，请参阅代码：

Private Sub GridView1_RowDataBound(sender As Object, e As GridViewRowEventArgs) Handles GridView1.RowDataBound
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim LButton = CType(e.Row.FindControl("lnkDownload"), System.Web.UI.WebControls.LinkButton)
        Dim scriptManager__1 = ToolkitScriptManager.GetCurrent(Me.Page)
        If scriptManager__1 IsNot Nothing Then
            scriptManager__1.RegisterPostBackControl(LButton)
        End If
    End If
End Sub

如何使用Gridview的linkbutton从数据库下载image / pdf文件？

1 个答案: