对于“动态”属性，C# .NET 4 中 PHP 的 isset 等效项是什么？物体？
我目前正在使用 MVC 3，其中使用 ViewBag。我想测试 ViewBag 的属性之一是否已分配。我知道在 PHP 中你可以做 isset(variable)，但是 .NET 4 中有类似的东西吗？
场景是我正在制作一个嵌套布局，它通过 ViewBag 获取部分标题和部分副标题。它们由分隔符分隔，并且副标题是可选的。如果未设置子标题，我不想显示分隔符。
这就是我想象的 isset 将被 .NET 4 等效项取代的情况。
@section header
{
<h2>@ViewBag.SectionTitle</h2>
@if(isset(ViewBag.SectionSubTitle))
{
<div id="section-title-seperator"> - </div><h3>@ViewBag.SectionSubTitle</h3>
}
}
除了直接回答我的问题之外，我还愿意接受替代解决方案（以防我滥用 ViewBag）。
提前致谢。
I am working with MVC 3 at the moment where I use the ViewBag. I would like to test if one of the properties of the ViewBag has been assigned. I know in PHP you could do isset(variable), but is there something similar in .NET 4?
The scenario is that I am making a nested layout which takes a section title and a section subtitle through the ViewBag. They are seperated by a seperator and the sub title is optional. I don't want to display the seperator if the sub title is not set.
This is how I imagine it where isset would be replaced by the .NET 4 equivelant.
@section header
{
<h2>@ViewBag.SectionTitle</h2>
@if(isset(ViewBag.SectionSubTitle))
{
<div id="section-title-seperator"> - </div><h3>@ViewBag.SectionSubTitle</h3>
}
}
Next to the direct answer to my question, I'm also open to alternate solutions (in case I'm abusing the ViewBag).
Thanks in advance.
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您可以像这样检查它是否为
null：@if(ViewBag.SectionSubTitle != null)。PHP 中的 isset() 实际上只是检查是否存在值。从手册：
您还可以使用
ViewDataDictionary.ContainsKey在您的ViewData属性上。因为ViewData["SectionSubTitle"]等同于ViewBag.SectionSubTitle所以在这种情况下你可以这样做：@if(ViewData.ContainsKey("SectionSubTitle"))You can check if it is
nulllike this:@if(ViewBag.SectionSubTitle != null).isset()in PHP actually just checks if there is a value present. From the manual:You can also use
ViewDataDictionary.ContainsKeyon yourViewDataproperty. BecauseViewData["SectionSubTitle"]is equavilient toViewBag.SectionSubTitleso in this case you could do:@if(ViewData.ContainsKey("SectionSubTitle"))