Asp.net-mvc – Custom DateTime model binder in Asp.net MVC

asp.net-mvcbindingcustom-model-bindermodelbinders

I would like to write my own model binder for DateTime type. First of all I'd like to write a new attribute that I can attach to my model property like:

[DateTimeFormat("d.M.yyyy")]
public DateTime Birth { get; set,}

This is the easy part. But the binder part is a bit more difficult. I would like to add a new model binder for type DateTime. I can either

  • implement IModelBinder interface and write my own BindModel() method
  • inherit from DefaultModelBinder and override BindModel() method

My model has a property as seen above (Birth). So when the model tries to bind request data to this property, my model binder's BindModel(controllerContext, bindingContext) gets invoked. Everything ok, but. How do I get property attributes from controller/bindingContext, to parse my date correctly? How can I get to the PropertyDesciptor of property Birth?

Edit

Because of separation of concerns my model class is defined in an assembly that doesn't (and shouldn't) reference System.Web.MVC assembly. Setting custom binding (similar to Scott Hanselman's example) attributes is a no-go here.

Best Answer

you can change the default model binder to use the user culture using IModelBinder

public class DateTimeBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
        bindingContext.ModelState.SetModelValue(bindingContext.ModelName, value);

        return value.ConvertTo(typeof(DateTime), CultureInfo.CurrentCulture);
    }
}

public class NullableDateTimeBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
        bindingContext.ModelState.SetModelValue(bindingContext.ModelName, value);

        return value == null
            ? null 
            : value.ConvertTo(typeof(DateTime), CultureInfo.CurrentCulture);
    }
}

And in the Global.Asax add the following to Application_Start(): 

ModelBinders.Binders.Add(typeof(DateTime), new DateTimeBinder());
ModelBinders.Binders.Add(typeof(DateTime?), new NullableDateTimeBinder());

Read more at this excellent blog that describe why Mvc framework team implemented a default Culture to all users.

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