使用客户端 JavaScript 在 X 秒后自动隐藏 ASP.NET 2.0 控制

引言

我需要一种方法来在几秒钟后隐藏一个 ASP.NET Label 控件。我有一个页面，用户可以在文本框中输入一些文本，单击“提交”，然后显示一个标签“已保存！”——我希望该标签在几秒钟后消失，以防用户想要编辑文本并再次保存，从而在几秒钟内再次显示保存的标签。

没什么太复杂的，只是 VB 代码，它遍历页面上的所有控件，查找 ID 的前几个字符与“lblStatus”或“lblSaved”匹配的 Label 控件，然后编写 JavaScript 代码块在几秒钟后隐藏这些控件。

我将这段代码应用于一个名为“commonFunctions”的类中，并在我的母页的 Load 事件中调用它

commonFunctions.hideAllStatusLabelsAfterXSecs(Page)

希望这段代码不难理解，您可以根据自己的需要进行修改。它可以应用于任何类型的控件，而不仅仅是 Label。

Public Shared Function hideAllStatusLabelsAfterXSecs(ByVal mePage As Page)
        ' hide all "lblStatus" and "lblSaved" labels after X seconds


        ' based on this javascript:

        ' <script type='text/javascript'>

        ' if (document.getElementById('control_id') != null)

        ' var x1 = setTimeout("document.getElementById('control_id').

        '                               style.display='none'", 2000);

        ' </script>


        ' ^^ control_id is control.ClientID in ASP.NET 2.0 code


        ' # of seconds until hide

        Dim xsecs As Integer = 2

        ' convert request seconds into js seconds

        Dim realSecs As Integer = xsecs * 1000

        ' define the script string to add to the page

        Dim theScript As New StringBuilder

        ' js header

        theScript.Append("<script type='text/javascript'>" + vbCrLf)
        theScript.Append("// hide all status labels after X seconds" + vbCrLf)

        ' iterate through all page controls

        Dim oControl As Control
        Dim childc As Control
        Dim labelall As Label
        Dim countControls As Integer = 0
        Dim jsCtrlStr As String ' document.getElementByID('ctrl_id')


        For Each oControl In mePage.Form.Controls
            For Each childc In oControl.Controls
                ' is it a label?

                If TypeOf childc Is Label Then
                    labelall = CType(childc, Label)

                    ' is it a label we want to hide after X seconds?

                    If Left(childc.ID.ToString, 9) = "lblStatus" Or _
                        Left(childc.ID.ToString, 8) = "lblSaved" Then

                        ' increment variable so no two vars are the same in js

                        countControls = countControls + 1

                        ' define js control string

                        jsCtrlStr = "document.getElementById('" & _
                                             childc.ClientID & "')"

                        ' is the control currently visible? script error otherwise

                        theScript.Append("if (" & jsCtrlStr & " != null) ")

                        ' rest of js

                        theScript.Append("var x" & countControls.ToString & _
                            " = setTimeout(""" & jsCtrlStr & _
                            ".style.display='none'"", " & _
                            realSecs.ToString & ");" + vbCrLf)
                    End If
                End If
            Next
        Next

        ' js close block

        theScript.Append("</script>")

        'test: show client js block, stop

        'System.Web.HttpContext.Current.Response.Write(theScript.ToString)

        'System.Web.HttpContext.Current.Response.End()


        ' add js block to page

        mePage.ClientScript.RegisterStartupScript(GetType(String), _
                         "HideLabelControls", theScript.ToString)

        Return "0"
    End Function