Display/Edit a Currency in ASP.NET MVC Core, why so complicated?

Question

In an ASP.NET Core 2.0 application, I have a Foo class with a lot of classical string or numeric members and also a int? Budget fi

Answer 1

My biggest finding was to ensure you are not just rendering the field via your own tag within the .cshtml; rather, ensure you are using the @Html.EditorFor() syntax to render the field:

                <div class="col-md-10">
                    @Html.EditorFor(model => Model.AmountPaid)
                    <span asp-validation-for="AmountPaid" class="text-danger" />
                </div>

Once I used this, the validation worked correctly. You can also decorate your field, such as:

    [DataType(DataType.Currency)]
    [Column(TypeName = "decimal(18, 2)")]
    public decimal AmountPaid { get; set; }

https://docs.microsoft.com/en-us/aspnet/core/tutorials/razor-pages/validation?view=aspnetcore-2.2

Answer 2

I noticed that InputTagHelper has a Format property, which means one can write :

<input asp-for="Budget" asp-format="{0:C}" class="form-control" />

Finding that though was not easy. It wasn't mentioned in the Input Tag Helper section of the intro. In the end I found it through ASP.NET Core MVC Input Tag Helper Deep Dive

Now I understand why people say ASP.NET Core's documentation is lacking - the intro goes to great lenghts to explain the various tag helpers in a single article, explains their relation to HTML Helpers, but ommits significant properties like Format. Without direct link to the class's documentation, it takes a bit of digging to find it.

There are quite a few similar questions in SO with answers that say "you can't format" or propose custom solutions.

UPDATE

An issue was opened on July 2017 about POSTing currency values that included a currency symbol. The thread is insteresting as it explains that asp-format only affects display, so the recommended solution is to put the symbol outside the input, possibly using Bootstrap input groups :

The recommended solution here is to place the currency indicator outside of the editable field (e.g. before or after)

Perhaps something like this:

<div class="input-group">
    <input asp-for="Budget" asp-format="{0:#,###.00}" class="form-control" />
    <span class="input-group-addon">€</span>
</div>