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Layout has this:
<!DOCTYPE html>
<html>
<head>
<environment names="Development">@RenderSection("devCss", required: false)</environment>
<environment names="Staging,Production">@RenderSection("staproCss", required: false)</environment>
</head>
<body>
@RenderBody()
<environment names="Development">@RenderSection("devJs", required: false)</environment>
<environment names="Staging,Production">@RenderSection("staproJs", required: false)</environment>
</body>
</html>
View has this:
@section devCss { <link rel="stylesheet" href="foo.css" asp-append-version="true" /> }
@section staproCss { <link rel="stylesheet" href="foo.min.css" asp-append-version="true" /> }
@section devJs {}
@section staproJs {}
<h1>hello</h1>
When RenderSection() is outside the <environment> tag, everything works.
When inside, as in above example, it fails with the unhelpful error of InvalidOperationException: The following sections have been defined but have not been rendered by the page at '_Layout.cshtml': 'staproCss, staproJs'. To ignore an unrendered section call IgnoreSection("sectionName").
That obviously makes no sense, as all sections were defined. And it complained about some, and not the others.
Does the <environment> tag-helper allow RenderSection() within it?
945
Just Add @RenderSection("Scripts", required: false) in end of </body> tag.
53
This answer is thanks to a comment by @user2818985.
The environment which is not defined, will not emit the content within. Which means it won't emit the RenderSection() call. Which means the view will define a section foo { ... } which doesn't exist. Which fails, and thus the exception.
To accomplish my original goal, I updated the layout:
@inject Microsoft.AspNetCore.Hosting.IHostingEnvironment _env
<!DOCTYPE html>
<html>
<head>
<environment names="Development">
@RenderSection("devCss", required: false)
</environment>
<environment names="Staging,Production">
@RenderSection("staproCss", required: false)
</environment>
@if (_env.EnvironmentName == "Development" && IsSectionDefined("staproCss"))
{
IgnoreSection("staproCss");
}
@if (_env.EnvironmentName == "Staging,Production" && IsSectionDefined("devCss"))
{
IgnoreSection("devCss");
}
</head>
<body>
@RenderBody()
<environment names="Development">
@RenderSection("devJs", required: false)
</environment>
<environment names="Staging,Production">
@RenderSection("staproJs", required: false)
</environment>
@if (_env.EnvironmentName == "Development" && IsSectionDefined("staproJs"))
{
IgnoreSection("staproJs");
}
@if (_env.EnvironmentName == "Staging,Production" && IsSectionDefined("devJs"))
{
IgnoreSection("devJs");
}
</body>
</html>
So the sections are always defined, and so the child views never throw.
44
No, the environment tag is used to render different HTML based upon the environment defined by the ASPNET_ENV environment variable. For example, a different set of CSS definitions can be used for a development environment as compared to a production environment.
This link may also be helpful: A Complete Guide to the MVC 6 Tag Helpers
You can use the environment variable value in your website logic as shown here.
See this link for more information: Working with Multiple Environments
26
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