Viewdata 的 Javascript 错误
我有一个链接到一个控制器，该控制器呈现包含此 javascript 的页面。
$(document).ready(function () {
var creditCards = '<%:(ViewData["CreditCards"])%>';
alert(creditCards);
if (creditCards != null) {
var CreditCardViewData = '<%:((SelectList)ViewData["CreditCards"]).Count() %>';
....
我正在测试的情况是 viewData creditCards 为空。我调试它，它到达 varcreditCards = '<%:(ViewData["CreditCards"])%>'; 行，当我单击单步进入时，它会一直跳到 <代码>var CreditCardViewData = '<%:((SelectList)ViewData["CreditCards"]).Count() %>';. （注意：当ViewData CreditCards不为空时，该页面可以正常工作）
跳转后，立即给出错误：“argumentnullException：值不能为空。 参数名称：源。”
我如何防止出现此错误。谢谢
I have a link that goes to a controller that renders a page that includes this javascript.
$(document).ready(function () {
var creditCards = '<%:(ViewData["CreditCards"])%>';
alert(creditCards);
if (creditCards != null) {
var CreditCardViewData = '<%:((SelectList)ViewData["CreditCards"]).Count() %>';
....
The situation I am testing is when the viewData creditCards is null. I debug it and it gets to the var creditCards = '<%:(ViewData["CreditCards"])%>';line and when i click step into it jumps all the way to var CreditCardViewData = '<%:((SelectList)ViewData["CreditCards"]).Count() %>';. (Note: this page works fine when the ViewData CreditCards is not null)
After it jumps, it instantly gives the error: "argumentnullexception: Value cannot be null.
Parameter name: source."
How do i prevent this error from showing up. Thanks
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尝试将代码更改为以下内容，以确保仅在 ViewData["CreditCards"] 不为 null 时调用 Count()。
Count() 方法检查参数是否为 null，如果检测到无效 (null) 参数，则抛出 ArgumentNullException。
Try changing your code to the following to ensure that the Count() is only called if ViewData["CreditCards"] is not null.
The Count() method checks arguments for null and then throws the ArgumentNullException if it detects an invalid (null) argument.