我有一个使用 .net core 3.1 Razor 页面构建的 Web 应用程序。我需要添加从视图生成 PDF 的功能。通常，该库可以工作，因为我可以生成静态PDF，但是当我想使用模型为模板设定种子时，就会出现问题。
PageModel如下所示：
public class DetailsPdfModel : PageModel
{
private readonly ICablesData cablesData;
private readonly IConfiguration configuration;
public DetailsPdfModel(ICablesData cablesData, IConfiguration configuration)
{
this.cablesData = cablesData;
this.configuration = configuration;
}
public Cable Cable { get; set; }
public IActionResult OnGet(int cableId)
{
Cable = cablesData.GetById(cableId);
if (Cable == null)
{
return RedirectToPage("NotFound");
}
else
{
return new ViewAsPdf("DetailsPdf", this);
}
}
}
视图如下所示：
@page
@model DetailsPdfModel
@{
Layout = null;
}
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>DetailsPdf</title>
</head>
<body>
<p>@Model.Cable.Name</p>
</body>
</html>
当我尝试获取pdf时，会发生异常。我注意到@Model总是null.如果我将return new ViewAsPdf("DetailsPdf", this);更改为return Page();则@Model不是null而是之后只是常规视图而不是pdf文件。
有什么想法可以解决这个问题吗？
如果我更改返回新的ViewAsPdf("DetailsPdf"，this(; 返回Page((; @Model不为空，但之后只是常规视图而不是pdf文件。
这是因为ViewAsPdf不是为Razor Page设计的。而且Rotativa不会公开RazorPage的内置API。有关更多详细信息，请参阅 Rotativa.AspNetCore 的源代码。
作为演练，您可以创建自定义RazorPageAsPdf类来实现与以下相同的目标：
公共类详细信息pdf模型：页面模型 { ... publicIActionResultOnGet(int cableId(public RazorPageAsPdf OnGet(int cableId({ Cable = cablesData.GetById(cableId(; 如果(电缆 == 空( { 返回重定向到页面("未找到"(; } 还 {返回新的ViewAsPdf("DetailsPdf"，this(;返回新的 RazorPageAsPdf(this(;我们不需要页面路径，因为它可以通过当前路由确定 } } }
这是我对RazorPageAsPdf的实现，供您参考：
public class RazorPageAsPdf : AsPdfResultBase
{
private readonly IRazorViewEngine _razorViewEngine;
private readonly ITempDataProvider _tempDataProvider;
private readonly IRazorPageActivator _activator;
private string _razorPageName {get;set;}
public PageModel PageModel {get;set;}
public RazorPageAsPdf(PageModel pageModel)
{
PageModel = pageModel;
var httpContext = pageModel.HttpContext;
this._razorPageName = httpContext.Request.RouteValues["page"].ToString().Trim('/');
if(string.IsNullOrEmpty(_razorPageName)){
throw new ArgumentException("there's no such a 'page' in this context");
}
this._razorViewEngine = httpContext.RequestServices.GetRequiredService<IRazorViewEngine>();
this._tempDataProvider= httpContext.RequestServices.GetRequiredService<ITempDataProvider>();
this._activator = httpContext.RequestServices.GetRequiredService<IRazorPageActivator>();
}
private ViewContext GetViewContext( ActionContext actionContext, IRazorPage page, StringWriter sw)
{
var view = new RazorView( _razorViewEngine, _activator, new List<IRazorPage>(), page, HtmlEncoder.Default, new DiagnosticListener(nameof(RazorPageAsPdf)));
return new ViewContext( actionContext, view, this.PageModel.ViewData, this.PageModel.TempData, sw, new HtmlHelperOptions());
}
private async Task<string> RenderPageAsString(ActionContext actionContext){
using (var sw = new StringWriter())
{
var pageResult = this._razorViewEngine.FindPage(actionContext, this._razorPageName);;
if (pageResult.Page == null)
{
throw new ArgumentNullException($"The page {this._razorPageName} cannot be found.");
}
var viewContext = this.GetViewContext(actionContext, pageResult.Page, sw);
var page = (Page)pageResult.Page;
page.PageContext = this.PageModel.PageContext;
page.ViewContext = viewContext;
_activator.Activate(page, viewContext);
await page.ExecuteAsync();
return sw.ToString();
}
}
protected override async Task<byte[]> CallTheDriver(ActionContext actionContext)
{
var html = await this.RenderPageAsString(actionContext);
// copied from https://github.com/webgio/Rotativa.AspNetCore/blob/c907afa8c7dd6a565d307901741c336c429fc698/Rotativa.AspNetCore/ViewAsPdf.cs#L147-L151
string baseUrl = string.Format("{0}://{1}", actionContext.HttpContext.Request.Scheme, actionContext.HttpContext.Request.Host);
var htmlForWkhtml = Regex.Replace(html.ToString(), "<head>", string.Format("<head><base href="{0}" />", baseUrl), RegexOptions.IgnoreCase);
byte[] fileContent = WkhtmltopdfDriver.ConvertHtml(this.WkhtmlPath, this.GetConvertOptions(), htmlForWkhtml);
return fileContent;
}
protected override string GetUrl(ActionContext context) => string.Empty;
}