我正在Blazor Webassembly中尝试预呈现。我首先在Visual Studio中创建了一个托管的Blazor-wasm应用程序，然后将以下_host.cshtml文件添加到服务器项目中：
@page
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@using Amjad.Client.Pages
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Junk</title>
<base href="~/" />
<environment include="Development">
<link rel="stylesheet" href="css/bootstrap/bootstrap.min.css" />
<link rel="stylesheet" href="Amjad.Client.css.app.css" />
</environment>
<environment exclude="Development">
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css"
asp-fallback-href="css/bootstrap/bootstrap.min.css"
asp-fallback-test-class="sr-only" asp-fallback-test-property="position" asp-fallback-test-value="absolute"
crossorigin="anonymous"
integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T"/>
</environment>
<link href="css/site.css" rel="stylesheet" />
<link href="Amjad.Client.css/app.css" rel="stylesheet" />
</head>
<body>
<component type="typeof(App)" render-mode="WebAssemblyPrerendered" />
<script src="_framework/blazor.server.js"></script>
</body>
</html>
当我运行应用程序时，我得到以下运行时错误：
ArgumentException: A value for the 'render-mode' attribute must be supplied to the 'component' tag helper. (Parameter 'RenderMode')
Microsoft.AspNetCore.Mvc.TagHelpers.ComponentTagHelper.ProcessAsync(TagHelperContext context, TagHelperOutput output)
Stack Query Cookies Headers Routing
ArgumentException: A value for the 'render-mode' attribute must be supplied to the 'component' tag helper. (Parameter 'RenderMode')
Microsoft.AspNetCore.Mvc.TagHelpers.ComponentTagHelper.ProcessAsync(TagHelperContext context, TagHelperOutput output)
Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner.<RunAsync>g__Awaited|0_0(Task task, TagHelperExecutionContext executionContext, int i, int count)
Junk.Pages.Pages__Host.<ExecuteAsync>b__24_1() in _Host.cshtml
+
</body>
为什么在我已经给出渲染模式值的情况下要求渲染模式值？
找到了解决方案。我在服务器项目的Startup.cs中有这样的代码：
app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapControllers();
endpoints.MapFallbackToFile("/_Host");
});
这需要更改为：
app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapControllers();
endpoints.MapFallbackToPage("/_Host");
});
我不明白为什么这会导致我原来帖子中显示的错误。