IViewLocationExpander API

• ExpandViewLocations Razor视图路径，视图引擎会搜索该路径.
• PopulateValues 每次调用都会填充路由

项目目录如下所示

创建区域扩展器，其实我并不需要多区域，我目前只需要达到一个区域中有多个文件夹进行存放我的视图.

所以我通过实现IViewLocationExpander进行扩展添加我自定义视图路径规则即可正如下代码片段

 public class MyViewLocationExpander : IViewLocationExpander
    {
        public IEnumerable<string> ExpandViewLocations(ViewLocationExpanderContext context, IEnumerable<string> viewLocations)
        {
            if (context.ControllerName != null && context.ControllerName.StartsWith("App"))
            {
                viewLocations = viewLocations.Concat(
                    new[] { $"/Areas/sysManage/Views/App/{context.ControllerName}/{context.ViewName}{RazorViewEngine.ViewExtension}"
                           });
                return viewLocations;
            }
            if (context.AreaName != "sysManage") return viewLocations;
            viewLocations = viewLocations.Concat(
                new[] { $"/Areas/sysManage/Views/System/{context.ControllerName}/{context.ViewName}{RazorViewEngine.ViewExtension}"
                });
            return viewLocations;
        }
        public void PopulateValues(ViewLocationExpanderContext context)
        {
        }
    }

在Startup.ConfigureServices 注册

  public void ConfigureServices(IServiceCollection services)  
        {  
            services.Configure<RazorViewEngineOptions>(o => {  
                o.ViewLocationExpanders.Add(new MyViewLocationExpander());  
            });  
            services.AddMvc();  
        } 

 app.UseEndpoints(endpoints =>
            {
                endpoints.MapRazorPages();
                endpoints.MapAreaControllerRoute(
                    name: "sysManage", "sysManage",
                    pattern: "{area:exists}/{controller=Home}/{action=Index}/{id?}");
            });

最终路由指向的还是

/SysManage/Controller/Action

---

ASP.NET Core自定义View查找路径，实现主题切换（IViewLocationExpander）

目的：修改视图的查找路径

PopulateValues方法：每次http请求都会执行
ExpandViewLocations方法：根据context.Values的值缓存执行。相同值，此方法只会执行一次
viewLocations参数：默认查找路径

方案1：

案例中使用Query参数中获取theme，项目中可以改成从配置文件中获取（在中间件中修改，通过HttpContext.Items传递参数）

public class ThemeViewLocationExpander : IViewLocationExpander
    {
        public void PopulateValues(ViewLocationExpanderContext context)
        {
            string theme = context.ActionContext.HttpContext.Request.Query["theme"].ToString();
            context.Values["theme"] = theme;
        }
        //有缓存，context.Values["theme"]相同值只会执行一次此方法
        public IEnumerable<string> ExpandViewLocations(ViewLocationExpanderContext context, IEnumerable<string> viewLocations)
        {
            string theme = context.Values["theme"];
            if (string.IsNullOrWhiteSpace(theme))
            {
                theme = "default";
            }
            string[] newLocation = { $"Views/{theme}/{{1}}/{{0}}.cshtml" };//2代表Area、1代表Controller、0代表Action
            return viewLocations.Union(newLocation);
        }

    }

ConfigureServices方法中添加：

//配置模版视图路径
            services.Configure<RazorViewEngineOptions>(options =>
            {
                options.ViewLocationExpanders.Add(new ThemeViewLocationExpander());
            });

方案2

services.Configure<RazorViewEngineOptions>(options =>
{
    第二种定位自定义页面文件的位置
    //options.AreaViewLocationFormats.Clear();
    //options.AreaViewLocationFormats.Add("/Areas/{2}/Views/{1}/{0}.cshtml");
    //options.AreaViewLocationFormats.Add("/Areas/{2}/Views/Shared/{0}.cshtml");
    //options.AreaViewLocationFormats.Add("/Views/Shared/{0}.cshtml");
});