ASP.NET 核心 Razor 页面绑定属性和保存数据 model

Question

I have a question about model binding in razor pages .net core 3.1. Lets say I have a model such as this:

    public Boolean bEmailMessages { get; set; }
    public string sUserEmail { get; set; }
    public Boolean bIcal { get; set; }
    public Boolean bEventNotice { get; set; }

    public string EPRLogin { get; set; }
    public string EPRPWD { get; set; }
    public string EPRLaunch { get; set; }

On one of my razor pages I use this model for only the top 4 items as inputs that are bound to those items. In my constructor I am initializing this model with data from the database. On my HTTPPOST I get the model back, but the last 3 items are null (EPRLogin, EPRPWD, and EPRLaunch) because I have another page where the user updates those items.

Is there a way to preserve the data in that model and only have the binding update the data from the page? The reason I ask, is because I have a function that I get the model from and I send it to save it to the database.

The only way I can think of doing this would be to get my model within the save method, change only the items I got back from the page model and then send my modified model to be saved.

I hope I explained this well enough...

Answer 1

As you said, I think the best way is to update only the first four items. Below is a work demo.

You can add an Id into your model.

Then in your pagemodel(Assuming Id=1 is the initial value):

public IActionResult OnGet()
    {
        Simple = _context.Simples.Find(1);
        return Page();
    }

    public IActionResult OnPost(Simple simple)
    {
        _context.Simples.Attach(simple);
        _context.Entry(simple).Property(x => x.bEmailMessages).IsModified = true;
        _context.Entry(simple).Property(x => x.bEventNotice).IsModified = true;
        _context.Entry(simple).Property(x => x.bIcal).IsModified = true;
        _context.Entry(simple).Property(x => x.sUserEmail).IsModified = true;
        _context.SaveChanges();
        if (!ModelState.IsValid)
        {
            return Page();
        }
        return RedirectToPage("./Index");
    }
}

And your page:

<form method="post">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <input type="hidden" asp-for="Simple.Id" />
            <div class="form-group">
                <label asp-for="Simple.bEmailMessages" class="control-label"></label>
                <input asp-for="Simple.bEmailMessages" />
                <span asp-validation-for="Simple.bEmailMessages" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Simple.bEventNotice" class="control-label"></label>
                <input asp-for="Simple.bEventNotice" />
                <span asp-validation-for="Simple.bEventNotice" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Simple.bIcal" class="control-label"></label>
                <input asp-for="Simple.bIcal" />
                <span asp-validation-for="Simple.bIcal" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Simple.sUserEmail" class="control-label"></label>
                <input asp-for="Simple.sUserEmail" class="form-control" />
                <span asp-validation-for="Simple.sUserEmail" class="text-danger"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Save" class="btn btn-default" />
            </div>
        </form>

Result: