Working with Razor Pages in ASP .NET Core

Use the page as a view model, to bind property use the [BindProperty] attribute.

In Razor HTML use the asp-for to do the binding

<input type='password' class="form-control" id='passcode' placeholder='passcode' asp-for="Password"  />

Add action handlers such as OnGet or OnPost and make them return IActionResult.

public IActionResult OnPost()
{
    return RedirectToPage("Content");
}

Here is an example of a conditional display

@if (!string.IsNullOrEmpty(Model.Error))
{
    <div class="alert alert-danger mt-3">@Model.Error</div>
}

Example of injecting service defind in DI

@inject Microsoft.Extensions.Configuration.IConfiguration configuration

Loading partial views:

<partial name="~/Pages/SubViews/LogoImage.cshtml" model="configuration" />

When there are multiple forms - use asp-page-handler

<form action="post" asp-page-handler="edit">
 <button>Edit</button>
<form>

then, add appropriate page handler:

public IActionResult OnPostEdit() {
}

The same works for Get requests, however, it won't work unless the HTTP request includes the "?handler=[handler_name]" query parameter. Make sure to add a hidden input field like the one below if you want the OnGetLogin handler to be invoked

<form method="get">
  <input type="hidden" name="handler" value="login" />
  <button type="submit" class="btn btn-primary">Login</button>
</form>

Query parameters

<a asp-route-a="a" asp-route-b="b">Click Here</a>

This translates to ?a=a&b=b

Bindable properties in the page model:

[BindProperty]
public string Field1 { get; set; }
[BindProperty]
public string Field2 { get; set; }

To get the values back use:

<input type="text" asp-for="MyProp" value="@Model.MyProp"/>

Validation text

<span asp-validation-for="Field1" class="text-danger"></span>

When using a textarea, the asp-for does not work, so replace it with this code:

<textarea class="form-control" readonly name="@Html.NameFor(m => m.MyProp)">@Model.MyProp</textarea>

Using values from a query

[BindProperty(SupportsGet = true)]
[FromQuery(Name = "Id")]
public sint? Id { get; set; }

Return a file

private IActionResult Deliver(MemoryStream memoryStream, string mimetype)
{
    memoryStream.Seek(0, SeekOrigin.Begin);

    return new FileStreamResult(memoryStream, mimetype)
    {
        FileDownloadName = "report.pdf"
    };
}

Create an Excel report

XLWorkbook wb = new();
IXLWorksheet ws = wb.AddWorksheet();

ws.Cell(1, 1).SetValue("Field one");
ws.Cell(1, 2).SetValue("Field two");

ws.Cell(1, 1).SetValue("Field one value");
ws.Cell(1, 2).SetValue("Field two value");


ws.Columns().AdjustToContents();

MemoryStream memoryStream = new();

wb.SaveAs(memoryStream);

memoryStream.Seek(0, SeekOrigin.Begin);

return Deliver(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");