Vb.net 是否可以使用AJAX回发刷新CSS工作表？

我一直在学习如何使用ASP.NET3.5创建动态图像和动态样式表。我的理由是我有一个网页，我想改变标题背景图像（设置css）自动。检查下面的测试脚本：

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再说一次，没什么特别的。只需交换我临时硬编码到程序中的两个值，并更新标签文本

这是我的动态样式表：

<%@ Page Language="VB" %>

<%  
    Response.ContentType = "text/css"
    Dim qString As String = Request.QueryString("t")
    Dim bText As String = Request.QueryString("v")
    If String.IsNullOrEmpty(qString) Then qString = "blank"
    If String.IsNullOrEmpty(bText) Then bText = "Placeholder"
    Dim theColor, H1size, bannerImg As String
    Select Case qString
        Case "c"
            theColor = "green"
            H1size = 30
        Case "m"
            theColor = "blue"
            H1size = 26
        Case Else
            theColor = "red"
    End Select
    bannerImg = String.Format("image.aspx?t={0}&p={1}", Server.UrlEncode(bText), qString)

    %>

body { background-color: <%=theColor%>; }
.testheader { background: url(<%=bannerImg%>); background-repeat:no-repeat; height:120px; }
.testclass { font-size: <%=H1size%>px; border:1px solid yellow; margin-bottom:2em; }

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有了这些信息，我想知道AsyncPostBack是否可以刷新CSS，这样当我点击按钮2时图像就会改变。我愿意接受建议和/或“这是做这件事的愚蠢/艰难的方式，试试这个…”类型的反馈

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谢谢大家

既然你说你愿意接受建议。。。为什么要用AsyncPostBack和CSS来实现这一点？为什么不在单击按钮2时使用javascript onclick事件动态更改图像

编辑（回应以下帖子）：

不会有回发（如果这就是你所说的闪烁的意思）：你仍然可以对你正在做的任何事情使用AsyncPostBack，然后在onclick上启动一个额外的javascript函数

document.getElementById('headerimg').src='2.jpg';

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这将在不刷新任何页面的情况下将图像更改为新的源文件。

因此我发现：因为我在Default.aspx页面上设置了变量，所以每次单击按钮时，它都会将变量重置为默认值，使其看起来好像不起作用。我把变量移到了一个外部类中，一切都很顺利。谢谢

<%@ Page Language="VB" %>

<%  
    Response.ContentType = "text/css"
    Dim qString As String = Request.QueryString("t")
    Dim bText As String = Request.QueryString("v")
    If String.IsNullOrEmpty(qString) Then qString = "blank"
    If String.IsNullOrEmpty(bText) Then bText = "Placeholder"
    Dim theColor, H1size, bannerImg As String
    Select Case qString
        Case "c"
            theColor = "green"
            H1size = 30
        Case "m"
            theColor = "blue"
            H1size = 26
        Case Else
            theColor = "red"
    End Select
    bannerImg = String.Format("image.aspx?t={0}&p={1}", Server.UrlEncode(bText), qString)

    %>

body { background-color: <%=theColor%>; }
.testheader { background: url(<%=bannerImg%>); background-repeat:no-repeat; height:120px; }
.testclass { font-size: <%=H1size%>px; border:1px solid yellow; margin-bottom:2em; }

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    Response.ContentType = "image/jpeg"
    Response.Clear()
    Response.BufferOutput = True


    Try
        Dim oText As String = Server.HtmlDecode(Request.QueryString("t"))
        If String.IsNullOrEmpty(oText) Then oText = "Placeholder"

        Dim oPType As String = Server.HtmlDecode(Request.QueryString("p"))
        If String.IsNullOrEmpty(oPType) Then oPType = "none"

        Dim imgPath As String = ""

        Select Case oPType
            Case "c"
                imgPath = "img/banner_green.jpg"
            Case "m"
                imgPath = "img/banner_blue.jpg"
            Case Else
                Throw New Exception("no ptype")
        End Select

        Dim oBitmap As Bitmap = New Bitmap(Server.MapPath(imgPath))

        Dim oGraphic As Graphics = Graphics.FromImage(oBitmap)
        Dim frontColorBrush As New SolidBrush(Color.White)

        Dim oFont As New Font(FONT_NAME, 30)

        Dim oInfo() As ImageCodecInfo = ImageCodecInfo.GetImageEncoders
        Dim oEncoderParams As New EncoderParameters(1) 'jpeg
        Dim xOffset As Single = Math.Round((oBitmap.Height - oFont.Height) / 2, MidpointRounding.ToEven)

        Dim oPoint As New PointF(275.0F, xOffset + 10)

        oEncoderParams.Param(0) = New EncoderParameter(Encoder.Quality, 100L)

        oGraphic.TextRenderingHint = Drawing.Text.TextRenderingHint.AntiAlias
        oGraphic.DrawString(oText, oFont, frontColorBrush, oPoint)

        oBitmap.Save(Response.OutputStream, oInfo(1), oEncoderParams)

        Response.Output.Write(oBitmap)

        oBitmap.Dispose()
        oGraphic.Dispose()

        Response.Flush()
    Catch ex As Exception

    End Try
End Sub

document.getElementById('headerimg').src='2.jpg';