I wanted to know if it was possible to render a view from a class that is not a controller. Everything I see seems to say that you can't.
What I'm trying to do is to render a partial view from a WCF web service in order to push it somewhere else. Is it possible to use the view engine for that?
Thanks!
Update:
I keep getting argument null exception with the HtmlHelper. Here is my code and the stack trace. My partial is indeed named TableOfContent.cshtml and is located in the /View/Shared folder. Do I new to instantiate my ViewContext differently?
HtmlHelper helper = new HtmlHelper(new ViewContext(), viewData);
var a = helper.Partial("TableOfContent");
at System.Web.Mvc.ViewContext..ctor(ControllerContext controllerContext, IView view, ViewDataDictionary viewData, TempDataDictionary tempData, TextWriter writer)
at System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection)
at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName)
at SyncInvokeProcessEvent(Object , Object[] , Object[] )
at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
This will call the view without requiring a controller (for the partial view).
Html.Partial(partialViewName);
See also Html.Partial method overload
Here are two different ideas to consider:
I've done something similar using RazorEngine. Allows you to render razor templates to a string.
Create a controller and use WebClient to invoke the action. This assumes you have an MVC application.
Related
I am trying to use output caching on an HTML Helper. However, even with the attribute set, this code block is always entered when the Helper method is called. Since the outputcache attribute won't work in this scenario, what would be the recommended way of caching "expensive" queries in Html Helpers?
[OutputCache(Duration = 60)]
public static MvcHtmlString CountryDropDownListFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, object selectedValue)
{
var doc = new XmlDocument();
doc.Load(HttpContext.Current.Server.MapPath("~/App_Data/countries.xml"));
var items = new Dictionary<string, string>();
foreach (XmlNode node in doc.SelectNodes("//country"))
{
items.Add(node.InnerText, node.InnerText);
}
return html.DropDownListFor(expression, new SelectList(items, "key", "value", selectedValue));
}
Output caching lets you store the output of an action method in memory on the Web server. For example, if the action method renders a view, the view page will be cached. This cached page is then available to the application for subsequent requests. Output caching saves your application the time and resources it would take to re-create the result of the action method.
In ASP.NET MVC, you can use the OutputCacheAttribute attribute to mark action methods whose output you want to cache. If you mark a controller with the OutputCacheAttribute attribute, the output of all action methods in the controller will be cached.
details http://msdn.microsoft.com/en-us/library/system.web.mvc.outputcacheattribute(v=vs.108).aspx
You use this attribure for not action method
Correct Example
[OutputCache(Duration = 50000)]
public ActionResult CountryDropDownListFor()
{
// Code
}
And in your view you can use Html.PartialAction to render one
Does anybody know a way to turn off MVC3 automatically decorating primitive types with a data-val-* attribute.
DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes = false;
removes the data-val-required attribute, but I can't seem to find a way to turn off primitive types eg: data-val-number
I have a lot of hidden int fields which don't required validating on a form, but because of these attributes they are getting validated, causing my app to appear frozen.
I imagine that the hidden int fields have the [Required] data annotations defined on them in the viewmodel? If so then I believe you just need to remove the data annotation to prevent the data-val-required attribute from being displayed.
I could be wrong, but I suspect you will then say that the field is required when that viewmodel is used in some other views?
If this is the case, then rather than turning off the data annotations (which is essentially a work around) then you need to define your view models correctly. Ideally, each view model should be specific for the view that it is defined (see pattern 3 of the following link). This will avoid the issues where you have fields that are required on some views and are not required on others.
I couldn't seem to find a way to turn this off, so created my own HtmlHelper as a way to get around this issue.
public static IHtmlString HiddenInputFor<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression, IDictionary<string, object> htmlAttributes)
{
ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, helper.ViewData);
var memberExpression = (MemberExpression)expression.Body;
string fullID = helper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(memberExpression.Member.Name);
var builder = new TagBuilder("input");
builder.MergeAttribute("type", "hidden");
var value = ModelMetadata.FromLambdaExpression(expression, helper.ViewData).Model;
builder.MergeAttribute("value", value.ToString());
string fullName = helper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(ExpressionHelper.GetExpressionText(expression));
builder.MergeAttribute("name", fullName);
builder.GenerateId(fullID);
var tag = builder.ToString(TagRenderMode.SelfClosing);
return new HtmlString(tag);
}
I've noticed that if you load a partial view from an ajax request, the validations (data-val-*) inside the partial view are not automatically added. So I finally changed my code to load from ajax the heavy form data that doesn't need validations.
You can specify data-val="false" in the HTML input which you are creating on the page, for example:
<input type="checkbox" name="foo" value="#item.foo" class="input-validation-error"
data-val="false">
Is there a way that I can invoke the model binder for a single object?
I don't want/need a custom model binder - I just want to do something like this:
MyViewModel1 vModel1 = new MyViewModel1();
InvokeModelBinder(vModel1);
MyViewModel2 vModel2= new MyViewModel2();
InvokeModelBinder(vModel2);
And when I'm done, the properties of both vModel1 and vModel2 have been bound to what's in the incoming request. Because of the way that our controller/action is being written, I don't necessarily want to list vModel1 and vModel2 in the action method's input list (since there will end up being a potentially long list of view models to optionally bind against).
Use Controller.UpdateModel:
MyViewModel1 vModel1 = new MyViewModel1();
UpdateModel(vModel1);
Update
Note if ModelState in controller has validation errors (related to model passed in action), UpdateModel (with any model) throws excetion, despite UpdateModel success and vModel1 is updated. Therefore errors in ModelState should be removed, or put UpdateModel in try/catch and just ignore excetion
This is wrong on many levels IMHO:
This is not how ASP.NET MVC is designed to work.
Your actions do not define a clear contract of what data they expect.
What do you get out of it? Smells like bad design.
Model binding is driven by reflection. Before an action is invoked it will reflect the method parameters list and for each object and its properties it will invoke a model binder to find a value for each property from the various value providers (form POST values provider, url parameters, etc). During model binding the ModelState validation is done as well.
So by not using the default ASP.NET MVC to do this you are losing all that.
Even if you were to manually get hold of a model binder like that:
IModelBinder modelBinder = ModelBinders.Binders.GetBinder(typeof(MyObject));
MyObject myObject = (MyObject ) modelBinder.BindModel(this.ControllerContext, ** ModelBindingContext HERE**);
You can see that you need to initalize a ModelBindingContext, something that ASP.NET MVC will do internally based on the current property it is reflecting. Here is the snipped from the ASP.NET MVC source code:
protected virtual object GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) {
// collect all of the necessary binding properties
Type parameterType = parameterDescriptor.ParameterType;
IModelBinder binder = GetModelBinder(parameterDescriptor);
IDictionary<string, ValueProviderResult> valueProvider = controllerContext.Controller.ValueProvider;
string parameterName = parameterDescriptor.BindingInfo.Prefix ?? parameterDescriptor.ParameterName;
Predicate<string> propertyFilter = GetPropertyFilter(parameterDescriptor);
// finally, call into the binder
ModelBindingContext bindingContext = new ModelBindingContext() {
FallbackToEmptyPrefix = (parameterDescriptor.BindingInfo.Prefix == null), // only fall back if prefix not specified
ModelName = parameterName,
ModelState = controllerContext.Controller.ViewData.ModelState,
ModelType = parameterType,
PropertyFilter = propertyFilter,
ValueProvider = valueProvider
};
object result = binder.BindModel(controllerContext, bindingContext);
return result;
}
I was researching something and came across this blog post at buildstarted.com about model binders. It actually works pretty darn well for my purposes but I am not sure exactly whats going on behind the scenes. What I did was create a custom ModelBinder called USerModelBinder:
public class UserModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
ValueProviderResult value = bindingContext.ValueProvider.GetValue("id");
MyEntities db = new MyEntities();
User user = db.Users.SingleOrDefault(u => u.UserName == value.AttemptedValue);
return user;
}
}
Then in my Global.asax.cs I have:
ModelBinders.Binders.Add(typeof(User), new UserModelBinder());
My understanding is that using the model binder allows me to NOT have to use the following lines in every controller action that involves a "User". So instead of passing in an "id" to the action, the modelbinder intercepts the id, fetches the correct "item"(User in my case) and forwards it to the action for processing.
MyEntities db = new MyEntities();
User user = db.Users.SingleOrDefault(u => u.UserName == value.AttemptedValue);
I also tried using an annotation on my User class instead of using the line in Global.asax.cs:
[ModelBinder(typeof(UserModelBinder))]
public partial class User
{
}
I'm not looking for a 30 page white paper but I have no idea how the model binder does what it does. I just want to understand what happens from when a request is made to the time it is served. All this stuff "just working" is not acceptable to me, lol. Also, is there any difference between using the annotation versus adding it in Global.asax.cs? They seem to work the same in my testing but are there any gotchas?
Usually the Model Binder (in MVC) looks at you Action method and sees what it requires (as in, the objects types). It then tries to find the values from the HTTP Request (values in the HTTP Form, QueryString, Json and maybe other places such as cookies etc. using ValueProviders). It then creates a new object with the parameters that it retrieves.
IMO What you've done is not really "model binding". In the sense that you've just read the id and fetched the object from the DB.
example of usual model binding:
// class
public class SomeClass
{
public int PropA {get;set;}
public string PropB {get;set;}
}
// action
public ActionResult AddSomeClass(SomeClass classToBind)
{
// implementation
}
// pseudo html
<form action="">
<input name="PropA" type="text" />
<input name="PropB" type="text" />
</form>
if you post a form that contains the correct values (lets say you post a form with PropA and PropB ) the model binder can identify that you've sent those values in the form and build a SomeClass object.
If you really want to create a real working example you should use a strongly typed View and use HtmlHelper's EditorFor (or EditorForModel) to create all the correct names that MVC needs.
--
for reference MVC's default binder is the DefaultModelBinder, and some (there are more, you can look around in the System.Web.Mvc namespace) ValueProviders that it uses by default are the FormValueProvider and the QueryStringValueProvider
So, as I already said, how this basically works is that the default model binder reads the model that the action is recieving (say SomeClass in the example) reads what are the values that it can read (say PropA and PropB) and asks the ValueProviders for the correct values for the properties.
Also, if I recall correctly, you can also see the value providers in runtime using the ValueProviderFactories static class.
A ModelBinder looks at the arguments of the selected Controller action's method signature, then converts the values from the ValueProviders into those arguments.
This happens when the ControllerActionInvoker invokes the action associated with the ControllerContext, because the Controller's Execute() method told it to.
For more about the ASP.NET MVC execution process, see Understanding the MVC Application Execution Process
I have an action method that takes in a string as its only parameter. The action method transforms it, and returns the result back to the client (this is done on an ajax call). I need to allow markup in the string value. In the past, I've done this by decorating the property on my model with [AllowHtml], but that attribute cannot be used on a parameter and the AllowHtmlAttribute class is sealed, so I cannot inherit from it. I currently have a work around where I've created a model with just one property and decorated it with the aforementioned attribute, and this is working.
I don't think I should have to jump through that hoop. Is there something I'm missing, or should I make a request to the MVC team to allow this attribute to be used on method parameters?
If you need to allow html input for a particular parameter (opposed to "model property") there's no built-in way to do that because [AllowHtml] only works with models. But you can easily achieve this using a custom model binder:
public ActionResult AddBlogPost(int id, [ModelBinder(typeof(AllowHtmlBinder))] string html)
{
//...
}
The AllowHtmlBinder code:
public class AllowHtmlBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var request = controllerContext.HttpContext.Request;
var name = bindingContext.ModelName;
return request.Unvalidated[name]; //magic happens here
}
}
Find the complete source code and the explanation in my blog post: https://www.jitbit.com/alexblog/273-aspnet-mvc-allowing-html-for-particular-action-parameters/
Have you looked at ValidateInputAttribute? More info here: http://blogs.msdn.com/b/marcinon/archive/2010/11/09/mvc3-granular-request-validation-update.aspx.