I have a web app build with .net core 3.1 Razor Pages. I need to add functionality to generate a PDF from a view. Generally the library is working because i can generate a static PDF, but the problem occurs when I want to use model to seed the template.
The PageModel looks like this:
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);
}
}
}
The view looks like this:
@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>
When I am trying to get the pdf the exception occurs. I noticed that the @Model is always null. If I change the return new ViewAsPdf("DetailsPdf", this); to return Page(); the @Model is not null but after that is only regular view not the pdf file.
Any ideas how to solve this problem?
If I change the return new ViewAsPdf("DetailsPdf", this); to return Page(); the @Model is not null but after that is only regular view not the pdf file.
That's because ViewAsPdf is not designed for Razor Page. And Rotativa doesn't expose a built-in API for RazorPage. For more details, see source code of Rotativa.AspNetCore.
As a walkaround, you could create a custom RazorPageAsPdf class to achieve the same goal as below:
public class DetailsPdfModel : PageModel
{
...
public IActionResult OnGet(int cableId)
public RazorPageAsPdf OnGet(int cableId)
{
Cable = cablesData.GetById(cableId);
if (Cable == null)
{
return RedirectToPage("NotFound");
}
else
{
return new ViewAsPdf("DetailsPdf", this);
return new RazorPageAsPdf(this); // we don't need page path because it can be determined by current route
}
}
}
Here's my implementation of RazorPageAsPdf for your reference:
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;
}