最初我可以在选择图像后预览图像。添加母版页后，JavaScript 不再工作。
这是我的母版页
<%@ Master Language="C#" AutoEventWireup="true" CodeBehind="Site1.master.cs" Inherits="Testing.Site1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script type="text/javascript" src="http://code.jquery.com/jquery-1.8.2.js"></script>
<asp:ContentPlaceHolder ID="head" runat="server">
</asp:ContentPlaceHolder>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
</asp:ContentPlaceHolder>
</div>
</form>
</body>
</html>
这是我的内容页面
<%@ Page Language="C#" MasterPageFile="~/Site1.Master" AutoEventWireup="true" CodeBehind="Testing1.aspx.cs" Inherits="Testing.Testing1" %>
<asp:Content ID="Content2" ContentPlaceHolderID="head" runat="server">
<script type="text/javascript">
function imagepreview(input)
{
if (input.files && input.files[0]) {
var fildr = new FileReader();
fildr.onload = function (e) {
$('#Image1').attr('src', e.target.result);
};
fildr.readAsDataURL(input.files[0]);
}
}
</script>
</asp:Content>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
<asp:FileUpload ID="FileUpload1" runat="server" />
<br />
<asp:Image ID="Image1" runat="server" height="100" Width="100" />
<br />
<br />
<asp:Button ID="btnUpload" runat="server" Text="Upload" OnClick="btnUpload_Click" />
<br />
<br />
<asp:TextBox ID="tbRetrieve" runat="server"></asp:TextBox>
<br />
<asp:Button ID="btnRetrieve" runat="server" Text="Retrieve" OnClick="btnRetrieve_Click" />
<br />
<asp:Image ID="Image2" runat="server" />
<br />
<asp:Label ID="lblMessage" runat="server"></asp:Label>
<br />
<br />
</asp:Content>
这是我的代码
protected void Page_Load(object sender, EventArgs e)
{
FileUpload1.Attributes["onchange"] = "imagepreview(this)";
if (!IsPostBack)
{
lblMessage.Visible = false;
}
}
那么问题出在哪里？
最佳答案
添加母版页时，查找控件 ID 的代码将发生更改，您必须像这样替换代码。
<script type="text/javascript">
function imagepreview(input)
{
if (input.files && input.files[0]) {
var fildr = new FileReader();
fildr.onload = function (e) {
$('#<%=Image1.ClientID%>').attr('src', e.target.result);
};
fildr.readAsDataURL(input.files[0]);
}
}
关于添加母版页后 JavaScript 不工作，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42291122/