CODEWITHSUNDEEP
asp.net-mvcasp.net-web-api
coach_rob
coach_rob

Reputation: 901

ASP.NET MVC Web API Models that are not tied to query string parameters

I know how to create a model class that mirrors query string variables so that when it comes into my Web API controller action, the model is populated.

However, is there a way to make it so that I'm not locked into the query string variable names as the properties on my model class?

Example:

public class MyModel {
    public string o {get;set;}
}

public class MyController {
    public string Get(MyModel model) {

    }
}

Then, if my query string looks like: GET http://domain.com/?o=12345

Is there a way to name that model property "Order" or something instead of "o" and then have it populated with the value from "o="?

Upvotes: 0

Views: 648

Answers (2)

Radim Köhler
Radim Köhler

Reputation: 123891

Solution for this scenario is custom IValueProvider. This ASP.NET MVC extension point is the correct place, where we can bridge the QueryString keys into Model.Property names. In comparison with ModelBinder, this will target exactly what we need (while not introducing later issues, when even other value providers (FORM) accidently contains that key...)

There is good tutorial how to introduce the custom IValueProvider:

And there is an simple example which is able to provide values for Model "Order" property, coming as QueryString "o" key:

Factory

// Factory
public class MyValueProviderFactory : ValueProviderFactory
{
  public override IValueProvider GetValueProvider(ControllerContext ctx)
  {
    return new MyValueProvider(ctx);
  }
}

Provider

// Provider
class MyValueProvider : IValueProvider
{
  protected HttpRequestBase Request { get; set; }    
  public MyValueProvider(ControllerContext ctx)
  {
    Request = ctx.HttpContext.Request;
  }

  // our custom logic to test QueryString keys, and expected prefixes
  public bool ContainsPrefix(string prefix)
  {
    var containsSpecial =
      "Order".Equals(prefix, StringComparison.OrdinalIgnoreCase)
      && Request.QueryString.AllKeys.Contains("o"
                    , StringComparer.InvariantCultureIgnoreCase);
    return containsSpecial;
  }

  // Handling "Order" key
  public ValueProviderResult GetValue(string key)
  {
    if (!ContainsPrefix(key))
    {
      return null;
    }
    var values = Request.QueryString.GetValues("o");

    if (values.Any())
    {
      return new ValueProviderResult(values, values.First()
                                    , CultureInfo.CurrentCulture);
    }
    return null;
  }
}

And in the global.asax we have to inject it:

protected void Application_Start()
{
  ValueProviderFactories.Factories.Add(new MyValueProviderFactory());
  ...

Upvotes: 0

Kirill Bestemyanov
Kirill Bestemyanov

Reputation: 11964

You can create custom model binder that will bind data to model as you wish. To use it you should:

public string Get([ModelBinder(typeof(MyComplexTypeModelBinder))]MyModel model)
{
...
}

To create custom model binder you can inherit from IModelBinder or from DefaultModelBinder.

public class MyComplexTypeModelBinder : IModelBinder
{

  public Object BindModel(ControllerContext controllerContext,
                          ModelBindingContext bindingContext)
  {
     if (bindingContext == null)
         throw new ArgumentNullException("bindingContext");

     // Create the model instance (using the ctor you like best)
     var obj = new MyComplexType();

     // Set properties reading values from registered value providers
     obj.Order = FromPostedData<string>(bindingContext, "o");
     ...
     return obj;
}


private T FromPostedData<T>(ModelBindingContext context, String key)
{
   // Get the value from any of the input collections
   ValueProviderResult result;
   context.ValueProvider.TryGetValue(key, out result);

   // Set the state of the model property resulting from 
   context.ModelState.SetModelValue(key, result);
   // Return the value converted (if possible) to the target type
   return (T) result.ConvertTo(typeof(T));
}

Upvotes: 1

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