如何在 csharp cshtml ASP.NET 中的 select 选项下拉列表中打印 selected 字符串？

Question

我是 ASP.NET 的新人。我尝试在 select 选项下拉菜单中打印 selected 字符串，但出现编译错误。

Compilation Error Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0201: Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement

这是我的 cshtml 代码。

@{ string FromAMPM = "AM";  }

<select id="FromAMPM" name="FromAMPM" class="form-control js-select">
<option value=""></option>
<option value="AM" @if (FromAMPM == "AM") { "selected"; } else { ""; }>AM</option>
<option value="PM" @if (FromAMPM == "PM") { "selected"; } else { ""; }>PM</option>
</select>

怎么了？谢谢

Answer 1

最好的方法是分开逻辑和 html

 @{
    var FromAMPM = "PM";
    
    var items = new List<SelectListItem>
    {  
        new SelectListItem { Value= "",   Text="Select" },
        new SelectListItem { Value= "AM",  Text="AM" },
        new SelectListItem { Value="PM",   Text="PM"}
    };
}

您不需要 select 代码，它会自动 select asp-for 值

<select id="fromAMPM" asp-for="@FromAMPM" class="form-control js-select" asp-items="@items"></select>

Answer 2

您可以在您的情况下使用 ternary conditional operator：

@{ string FromAMPM = "AM";  }

<select id="FromAMPM" name="FromAMPM" class="form-control js-select">
  <option value=""></option>
  <option value="AM" @(FromAMPM == "AM" ? "selected='selected'" : "")>AM<</option>
  <option value="PM" @(FromAMPM == "PM" ? "selected='selected'" : "")>PM<</option>
</select>

如何在 csharp cshtml ASP.NET 中的 select 选项下拉列表中打印 selected 字符串？

How to print selected string in select option drop down in csharp cshtml ASP.NET?

javascript

c#

html

asp.net

razor