ASP.NET自定义模型绑定：DateTime

Question

The problem

At this point I have a problem where my Get action is trying to read a DateTime parameter in a diferent format that is sent.

While the DateTime sent has this format: 0:dd/MM/yyyy The Get Actions expects: 0:MM/dd/yyyy

The solution (maybe)

In order to change what the Get action is expecting I'm using a Custom Model Binding.

The GET Action

    public async Task<IActionResult> Details(int? id, [ModelBinder(typeof(PModelBinder))]DateTime date)

The ModelBinder class

Now here are a few things that are missing and I don't know how to complete it properly:

public class PModelBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        string theDate = bindingContext.HttpContext.Request.QueryString["date"]; 
        //What should I write inside the []? 
        //I've tried QueryString["date"] which is the name of the parameter but it says is wrong
        DateTime dt = new DateTime();
        bool success = DateTime.TryParse(date); //Should I apply ParseExact? How should I do it?
        if (success)
        {
            return new //what should I be returning here? dt?
        }

    }
}

I've several questions marked as comments in the code above since I'm just starting to understand Custom Model Binding. Hope anyone can give me some advice.

I'm following this article:

https://weblogs.asp.net/melvynharbour/mvc-modelbinder-and-localization

But it's from 2008!!! , Although it seems valid since it's exactly the problem I'm having with my GET Action (diferent date formats)

Update: aditional information

The parameter date is defined as:

    [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
    public DateTime FechaLInicioLiq { get; set; }

and the URL build when calling that GET Action has this structure for the date parameter:

date=10%2F11%2F2017%200%3A00%3A00

Answer 1

You have several issues with your model binder implementation:

1. Do not hardcode parameter name ( date ). Use bindingContext.ModelName instead.
2. You should handle situation if value was not actually provided. You could check it by comparing result of IValueProvider.GetValue() with ValueProviderResult.None .

Here is sample DateTime model binder that accomplish what you need:

public class DateTimeModelBinder : IModelBinder
{
    private readonly IModelBinder baseBinder = new SimpleTypeModelBinder(typeof(DateTime));

    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
        if (valueProviderResult != ValueProviderResult.None)
        {
            bindingContext.ModelState.SetModelValue(bindingContext.ModelName, valueProviderResult);

            var valueAsString = valueProviderResult.FirstValue;

            //  valueAsString will have a string value of your date, e.g. '31/12/2017'
            var dateTime = DateTime.ParseExact(valueAsString, "dd/MM/yyyy", CultureInfo.InvariantCulture);
            bindingContext.Result = ModelBindingResult.Success(dateTime);

            return Task.CompletedTask;
        }

        return baseBinder.BindModelAsync(bindingContext);
    }
}