ASP.NET MVC：我什么时候应该创建自定义视图引擎

什么是自定义视图引擎？

csharp
public class MyCustomViewEngine : VirtualPathProviderViewEngine
{
    public MyCustomViewEngine()
    {
        // 设置视图文件的查找位置
        ViewLocationFormats = new[]
        {
            "~/Views/{1}/{0}.txt",
            "~/Views/Shared/{0}.txt"
        };
        // 设置分部视图文件的查找位置
        PartialViewLocationFormats = new[]
        {
            "~/Views/{1}/{0}.txt",
            "~/Views/Shared/{0}.txt"
        };
    }
    protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
    {
        // 自定义分部视图的创建逻辑
        // ...
    }
    protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
    {
        // 自定义视图的创建逻辑
        // ...
    }
    public override bool FileExists(ControllerContext controllerContext, string virtualPath)
    {
        // 自定义文件存在性的判断逻辑
        // ...
    }
}

csharp
public class TxtViewEngine : VirtualPathProviderViewEngine
{
    public TxtViewEngine()
    {
        ViewLocationFormats = new[]
        {
            "~/Views/{1}/{0}.txt",
            "~/Views/Shared/{0}.txt"
        };
        PartialViewLocationFormats = new[]
        {
            "~/Views/{1}/{0}.txt",
            "~/Views/Shared/{0}.txt"
        };
    }
    protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
    {
        // 自定义分部视图的创建逻辑
        if (FileExists(controllerContext, partialPath))
        {
            return new TxtView(partialPath);
        }
        else
        {
            return base.CreatePartialView(controllerContext, partialPath);
        }
    }
    protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
    {
        // 自定义视图的创建逻辑
        if (FileExists(controllerContext, viewPath))
        {
            return new TxtView(viewPath);
        }
        else
        {
            return base.CreateView(controllerContext, viewPath, masterPath);
        }
    }
    public override bool FileExists(ControllerContext controllerContext, string virtualPath)
    {
        // 自定义文件存在性的判断逻辑
        string filePath = controllerContext.HttpContext.Server.MapPath(virtualPath);
        return File.Exists(filePath);
    }
}
public class TxtView : IView
{
    private readonly string _viewPath;
    public TxtView(string viewPath)
    {
        _viewPath = viewPath;
    }
    public void Render(ViewContext viewContext, TextWriter writer)
    {
        string filePath = viewContext.HttpContext.Server.MapPath(_viewPath);
        string content = File.ReadAllText(filePath);
        writer.Write(content);
    }
}