I have two custom binders to get DateTime and DateTime? to bind.
I'm registering them in the Global.asax like:
public class MvcApplication : HttpApplication
{
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
ModelBinders.Binders[typeof (DateTime)] = new DateTimeModelBinder();
//ModelBinders.Binders[typeof (DateTime?)] = new NullableDateTimeModelBinder();
//ModelBinders.Binders.Add(typeof (DateTime), new DateTimeModelBinder());
//ModelBinders.Binders.Add(typeof(DateTime?), new NullableDateTimeModelBinder());
}
}
I've also tried it like this:
ModelBinders.Binders.Add(typeof (DateTime), new DateTimeModelBinder());
ModelBinders.Binders.Add(typeof(DateTime?), new NullableDateTimeModelBinder());
However, they are never being hit.
The model binding classes are here (stolen from the Internet):
public class DateTimeModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
DateTime dateTime;
var isDate = DateTime.TryParse(value.AttemptedValue,
Thread.CurrentThread.CurrentUICulture,
DateTimeStyles.None,
out dateTime);
if (!isDate)
{
bindingContext.ModelState.AddModelError(bindingContext.ModelName,
$"Cannot bind value {value.AttemptedValue} to a DateTime");
return DateTime.UtcNow;
}
return dateTime;
}
}
and here:
public class NullableDateTimeModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
if (string.IsNullOrWhiteSpace(value.AttemptedValue))
{
return null;
}
DateTime dateTime;
var isDate = DateTime.TryParse(value.AttemptedValue, Thread.CurrentThread.CurrentUICulture, DateTimeStyles.None, out dateTime);
if (!isDate)
{
bindingContext.ModelState.AddModelError(bindingContext.ModelName, $"Cannot convert {value.AttemptedValue} to a DateTime.");
return DateTime.UtcNow;
}
return dateTime;
}
}
What as I missing?
Related
I have a modelbinder like this:
public class CustomQuarantineModelBinder : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.ModelType.GetInterfaces().Contains(typeof(IQuarantineControl))
{
return new QuarantineModelBinder();
}
return null;
}
}
public class QuarantineModelBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext modelBindingContext)
{
char[] delimeter = { '|' };
if (modelBindingContext == null)
{
throw new ArgumentNullException(nameof(modelBindingContext));
}
var model = Activator.CreateInstance(modelBindingContext.ModelType);
if (modelBindingContext.ModelType.GetInterfaces().Contains(typeof(IQuarantineControl)))
{
var qc = model as IQuarantineControl;
if (qc != null)
{
var request = modelBindingContext.HttpContext.Request;
string QuarantineControl = request.Form["QuarantineControl"];
if (!string.IsNullOrEmpty(QuarantineControl))
{
string[] components = QuarantineControl.Split(delimeter);
qc.QuarantineClear();
qc.QuarantineControlID = Convert.ToInt32(components[0]);
qc.QuarantineState = (QuarantineState)Convert.ToInt32(components[1]);
for (int i = 2; i < components.Length; i++)
{
qc.QuarantineReasons.Add(components[i]);
}
}
}
}
modelBindingContext.Result = ModelBindingResult.Success(model);
return Task.CompletedTask;
}
However, other fields in the model is getting turned as null or empty. I would like to set QuarantineState, QuarantineControlId etc.. without affecting other values. Thanks
When your custom IModelBinderProvider returns a binder, that binder is responsible for binding the entire type. If you wish to fall back to the default MVC binder for other properties, you will need to do so explicitly.
Perhaps something like;
public class CustomQuarantineModelBinder : IModelBinderProvider
{
private readonly IModelBinderProvider baseProvider;
public CustomQuarantineModelBinder(IModelBinderProvider baseProvider){
this.baseProvider = baseProvider;
}
public IModelBinder GetBinder(ModelBinderProviderContext context){
...
return new QuarantineModelBinder(BaseProvider.GetBinder(context));
}
}
public class QuarantineModelBinder : IModelBinder
{
private readonly IModelBinder binder;
public QuarantineModelBinder(IModelBinder binder){
this.binder = binder;
}
public Task BindModelAsync(ModelBindingContext modelBindingContext)
{
...
binder.BindModelAsync(modelBindingContext);
...
}
}
services.AddMvc(options =>
{
var baseProvider = options.ModelBinderProviders
.OfType<ComplexObjectModelBinderProvider>()
.First();
options.ModelBinderProviders.Insert(0, new CustomQuarantineModelBinder(baseProvider));
});
When the model object is posted the string values that are empty are converted to null. This is the default behavior of the MVC model binder.
You can try a workaround like this,
public sealed class EmptyStringModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext,
ModelBindingContext bindingContext)
{
bindingContext.ModelMetadata.ConvertEmptyStringToNull = false;
//Binders = new ModelBinderDictionary() { DefaultBinder = this };
return base.BindModel(controllerContext, bindingContext);
}
}
I am trying to apply custom model binder for DateTime type property of model.
Here is the IModelBinder and IModelBinderProvider implementations.
public class DateTimeModelBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.ModelType == typeof(DateTime))
{
return new BinderTypeModelBinder(typeof(DateTime));
}
return null;
}
}
public class DateTimeModelBinder : IModelBinder
{
private string[] _formats = new string[] { "yyyyMMdd", "yyyy-MM-dd", "yyyy/MM/dd"
, "yyyyMMddHHmm", "yyyy-MM-dd HH:mm", "yyyy/MM/dd HH:mm"
, "yyyyMMddHHmmss", "yyyy-MM-dd HH:mm:ss", "yyyy/MM/dd HH:mm:ss"};
private readonly IModelBinder baseBinder;
public DateTimeModelBinder()
{
baseBinder = new SimpleTypeModelBinder(typeof(DateTime), null);
}
public Task BindModelAsync(ModelBindingContext bindingContext)
{
if (bindingContext == null)
{
throw new ArgumentNullException(nameof(bindingContext));
}
var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
if (valueProviderResult != ValueProviderResult.None)
{
bindingContext.ModelState.SetModelValue(bindingContext.ModelName, valueProviderResult);
var value = valueProviderResult.FirstValue;
if (DateTime.TryParseExact(value, _formats, new CultureInfo("en-US"), DateTimeStyles.None, out DateTime dateTime))
{
bindingContext.Result = ModelBindingResult.Success(dateTime);
}
else
{
bindingContext.ModelState.TryAddModelError(bindingContext.ModelName, $"{bindingContext} property {value} format error.");
}
return Task.CompletedTask;
}
return baseBinder.BindModelAsync(bindingContext);
}
}
And here is the model class
public class Time
{
[ModelBinder(BinderType = typeof(DateTimeModelBinder))]
public DateTime? validFrom { get; set; }
[ModelBinder(BinderType = typeof(DateTimeModelBinder))]
public DateTime? validTo { get; set; }
}
And here is the controller action method.
[HttpPost("/test")]
public IActionResult test([FromBody]Time time)
{
return Ok(time);
}
When tested, the custom binder is not invoked but the default dotnet binder is invoked. According to the official documentation,
ModelBinder attribute could be applied to individual model properties
(such as on a viewmodel) or to action method parameters to specify a
certain model binder or model name for just that type or action.
But it seems not working with my code.
1. Reason
According to the [FromBody]Time time in your action, I guess you're sending a payload with Content-Type of application/json. In that case, when a json payload received, the Model Binding System will inspect the parameter time and then try to find a proper binder for it. Because the context.Metadata.ModelType equals typeof(Time) instead of the typeof(DateTime), and there's no custom ModelBinder for typeof(Time) , your GetBinder(context) method will return a null :
public class DateTimeModelBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.ModelType == typeof(DateTime)) // not typeof(Time)
{
return new BinderTypeModelBinder(typeof(DateTime));
}
return null;
}
}
Thus it falls back to the default model binder for application/json. The default json model binder uses Newtonsoft.Json under the hood and will simply deserialize the whole payload as an instance of Time. As a result, your DateTimeModelBinder is not invoked.
2. Quick Fix
One approach is to use application/x-www-form-urlencoded (avoid using the application/json)
Remove the [FromBody] attribute:
[HttpPost("/test2")]
public IActionResult test2(Time time)
{
return Ok(time);
}
and send the payload in the format of application/x-www-form-urlencoded
POST https://localhost:5001/test2
Content-Type: application/x-www-form-urlencoded
validFrom=2018-01-01&validTo=2018-02-02
It should work now.
3. Working with JSON
Create a custom converter as below :
public class CustomDateConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return true;
}
public static string[] _formats = new string[] {
"yyyyMMdd", "yyyy-MM-dd", "yyyy/MM/dd"
, "yyyyMMddHHmm", "yyyy-MM-dd HH:mm", "yyyy/MM/dd HH:mm"
, "yyyyMMddHHmmss", "yyyy-MM-dd HH:mm:ss", "yyyy/MM/dd HH:mm:ss"
};
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var dt= reader.Value;
if (DateTime.TryParseExact(dt as string, _formats, new CultureInfo("en-US"), DateTimeStyles.None, out DateTime dateTime))
return dateTime;
else
return null;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
serializer.Serialize(writer, value as string);
}
}
I simply copied your code to format the date.
Change your Model as below :
public class Time
{
[ModelBinder(BinderType = typeof(DateTimeModelBinder))]
[JsonConverter(typeof(CustomDateConverter))]
public DateTime? validFrom { get; set; }
[ModelBinder(BinderType = typeof(DateTimeModelBinder))]
[JsonConverter(typeof(CustomDateConverter))]
public DateTime? validTo { get; set; }
}
And now you can receive the time using [FromBody]
[HttpPost("/test")]
public IActionResult test([FromBody]Time time)
{
return Ok(time);
}
How to create a model binder for decimal numbers which will throw exception if users are sending it in a wrong format?
I need something like this:
2 = OK
2.123 = OK
2,123 = throw invalid format exception
Look at this article http://haacked.com/archive/2011/03/19/fixing-binding-to-decimals.aspx/
You can just use standard binder with simple check like this
public class DecimalModelBinder : IModelBinder
{
public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
{
ValueProviderResult valueResult = bindingContext.ValueProvider
.GetValue(bindingContext.ModelName);
ModelState modelState = new ModelState { Value = valueResult };
object actualValue = null;
if (valueResult.AttemptedValue.Contains(","))
{
throw new Exception("Some exception");
}
actualValue = Convert.ToDecimal(valueResult.AttemptedValue,
CultureInfo.CurrentCulture);
bindingContext.ModelState.Add(bindingContext.ModelName, modelState);
bindingContext.Model = actualValue;
return true;
}
}
EDIT: According to #Liam suggestion you have to add this binder to your configuration first
ModelBinders.Binders.Add(typeof(decimal), new DecimalModelBinder());
Above code throws exception in the case of bad decimal separater, but you should use model validation to detect that kind of errors. It is more flexible way.
public class DecimalModelBinder : IModelBinder
{
public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
{
ValueProviderResult valueResult = bindingContext.ValueProvider
.GetValue(bindingContext.ModelName);
ModelState modelState = new ModelState { Value = valueResult };
object actualValue = null;
try
{
if (valueResult.AttemptedValue.Contains(","))
{
throw new Exception("Some exception");
}
actualValue = Convert.ToDecimal(valueResult.AttemptedValue,
CultureInfo.CurrentCulture);
}
catch (FormatException e)
{
modelState.Errors.Add(e);
return false;
}
bindingContext.ModelState.Add(bindingContext.ModelName, modelState);
bindingContext.Model = actualValue;
return true;
}
}
you don't throw exception but just add validation error. You can check it in your controller later
if (ModelState.IsValid)
{
}
I am creating a custom model binder to initially load a model from the database before updating the model with incoming values. (Inheriting from DefaultModelBinder)
Which method do I need to override to do this?
You need to override the BindModel method of the DefaultModelBinder base class:
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
if (bindingContext.ModelType == typeof(YourType))
{
var instanceOfYourType = ...;
// load YourType from DB etc..
var newBindingContext = new ModelBindingContext
{
ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(() => instanceOfYourType, typeof(YourType)),
ModelState = bindingContext.ModelState,
FallbackToEmptyPrefix = bindingContext.FallbackToEmptyPrefix,
ModelName = bindingContext.FallbackToEmptyPrefix ? string.Empty : bindingContext.ModelName,
ValueProvider = bindingContext.ValueProvider,
};
if (base.OnModelUpdating(controllerContext, newBindingContext)) // start loading..
{
// bind all properties:
base.BindProperty(controllerContext, bindingContext, TypeDescriptor.GetProperties(typeof(YourType)).Find("Property1", false));
base.BindProperty(controllerContext, bindingContext, TypeDescriptor.GetProperties(typeof(YourType)).Find("Property2", false));
// trigger the validators:
base.OnModelUpdated(controllerContext, newBindingContext);
}
return instanceOfYourType;
}
throw new InvalidOperationException("Supports only YourType objects");
}
You'll want to override BindModel to do this.
I have written a Custom Model Binder which is supposed to map Dates, coming from URL-Strings (GET) according to the current culture (a sidenote here: the default model binder does not consider the current culture if you use GET as http-call...).
public class DateTimeModelBinder : IModelBinder
{
#region IModelBinder Members
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
if (controllerContext.HttpContext.Request.HttpMethod == "GET")
{
string theDate = controllerContext.HttpContext.Request.Form[bindingContext.ModelName];
DateTime dt = new DateTime();
bool success = DateTime.TryParse(theDate, System.Globalization.CultureInfo.CurrentUICulture, System.Globalization.DateTimeStyles.None, out dt);
if (success)
{
return dt;
}
else
{
return null;
}
}
return null; // Oooops...
}
#endregion
}
I registered the model binder in global.asax:
ModelBinders.Binders.Add(typeof(DateTime?), new DateTimeModelBinder());
Now the problem occurs in the last return null;. If I use other forms with POST, it would overwrite the already mapped values with null. How can I avoid this?
Thx for any inputs.
sl3dg3
Derive from DefaultModelBinder and then invoke the base method:
public class DateTimeModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
// ... Your code here
return base.BindModel(controllerContext, bindingContext);
}
}
Well, it is actually a trivial solution: I create a new instance of the default binder and pass the task to him:
public class DateTimeModelBinder : IModelBinder
{
#region IModelBinder Members
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
if (controllerContext.HttpContext.Request.HttpMethod == "GET")
{
string theDate = controllerContext.HttpContext.Request.Form[bindingContext.ModelName];
DateTime dt = new DateTime();
bool success = DateTime.TryParse(theDate, System.Globalization.CultureInfo.CurrentUICulture, System.Globalization.DateTimeStyles.None, out dt);
if (success)
{
return dt;
}
else
{
return null;
}
}
DefaultModelBinder binder = new DefaultModelBinder();
return binder.BindModel(controllerContext, bindingContext);
}
#endregion
}
One more possible solution is pass some of the best default model bidners into custom and call it there.
public class BaseApiRequestModelBinder : IModelBinder
{
private readonly IModelBinder _modelBinder;
public BaseApiRequestModelBinder(IModelBinder modelBinder)
{
_modelBinder = modelBinder;
}
public async Task BindModelAsync(ModelBindingContext bindingContext)
{
//calling best default model binder
await _modelBinder.BindModelAsync(bindingContext);
var model = bindingContext.Result.Model as BaseApiRequestModel;
//do anything you want with a model that was bind with default binder
}
}
public class BaseApiRequestModelBinderProvider : IModelBinderProvider
{
private IList<IModelBinderProvider> _modelBinderProviders { get; }
public BaseApiRequestModelBinderProvider(IList<IModelBinderProvider> modelBinderProviders)
{
_modelBinderProviders = modelBinderProviders;
}
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.ModelType == typeof(BaseApiRequestModel) || context.Metadata.ModelType.IsSubclassOf(typeof(BaseApiRequestModel)))
{
//Selecting best default model binder. Don't forget to exlude the current one as it is also in list
var defaultBinder = _modelBinderProviders
.Where(x => x.GetType() != this.GetType())
.Select(x => x.GetBinder(context)).FirstOrDefault(x => x != null);
if (defaultBinder != null)
{
return new BaseApiRequestModelBinder(defaultBinder);
}
}
return null;
}
//Register model binder provider in ConfigureServices in startup
services
.AddMvc(options => {
options.ModelBinderProviders.Insert(0, new BaseApiRequestModelBinderProvider(options.ModelBinderProviders));
})