ASP.NET Web API - ModelBinders

Question

I need to use a custom modelbinder of some kind to always treat incoming dates in UK format, i have setup a custom model binder and registered like so:

Globa         


        

Answer 1

You do not need a custom model binder for that. You should be good by changing the thread culture to UK or set your web.config settings for UK, if this is what your site is using all the time.

If not, you can still change the DateTimeFormatInfo for the CurrentCulture to UK one.

There is also a good post about model binders available here by Scott Hanselman.

You can put this in Global.asax:

ModelBinders.Binders[typeof(DateTime)] = new DateAndTimeModelBinder()  

Answer 2

Attribute routing seems to conflict with model binding. If you use attribute routing, you can wrap the global.asax configuration into a single GlobalConfiguration.Config call to avoid the initialisation issues:

GlobalConfiguration.Configure(config =>
{
    config.BindParameter(typeof(DateTime), new DateTimeModelBinder());
    config.MapHttpAttributeRoutes();
}

(This might be fixed in the upcoming ASP.NET 5 if it's related to bug #1165.)

Answer 3

I think you don't need a model binder. Your approach is incorrect. The right approach for dates is using a client side globalization library like the globalize library to parse dates formatted in any language and transform them into JavaScript date objects. Then you can serialize your datascript data structures in JSON with the browser JSON.stringify, and this should work. It is better to use always standard formats for dates and to use a formatter instead than a model binder. Available formatters handle also TimeZones correctly, if you use the kind parameter of your C# DateTime objects to specify if the date time is expressed in local time or in UTC time.

Answer 4

You can register a model binder globally by implementing a ModelBinderProvider and inserting it into the list of services.

Example use in Global.asax:

GlobalConfiguration.Configuration.Services.Insert(typeof(ModelBinderProvider), 0, new Core.Api.ModelBinders.DateTimeModelBinderProvider());

Below is example code demonstrating a ModelBinderProvider and a ModelProvider implemenation that converts DateTime arguments in a culture aware manner (using the current threads culture);

DateTimeModelBinderProvider implementation:

using System;
using System.Web.Http;
using System.Web.Http.ModelBinding;

...

public class DateTimeModelBinderProvider : ModelBinderProvider
{
    readonly DateTimeModelBinder binder = new DateTimeModelBinder();

    public override IModelBinder GetBinder(HttpConfiguration configuration, Type modelType)
    {
        if (DateTimeModelBinder.CanBindType(modelType))
        {
            return binder;
        }

        return null; 
    }
}

DateTimeModelBinder implementation:

public class DateTimeModelBinder : IModelBinder
{
    public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
    {
        ValidateBindingContext(bindingContext);

        if (!bindingContext.ValueProvider.ContainsPrefix(bindingContext.ModelName) ||
            !CanBindType(bindingContext.ModelType))
        {
            return false;
        }

        bindingContext.Model = bindingContext.ValueProvider
            .GetValue(bindingContext.ModelName)
            .ConvertTo(bindingContext.ModelType, Thread.CurrentThread.CurrentCulture);

        bindingContext.ValidationNode.ValidateAllProperties = true;

        return true;
    }

    private static void ValidateBindingContext(ModelBindingContext bindingContext)
    {
        if (bindingContext == null)
        {
            throw new ArgumentNullException("bindingContext");
        }

        if (bindingContext.ModelMetadata == null)
        {
            throw new ArgumentException("ModelMetadata cannot be null", "bindingContext");
        }
    }

    public static bool CanBindType(Type modelType)
    {
        return modelType == typeof(DateTime) || modelType == typeof(DateTime?);
    }
}