MVC中的模型綁定字符串字段

Question

好的，我在MVC上遇到問題，我將控制器/視圖連接到多個模型，這些模型包含字符串的受保護內部集。 創建這些對象時，我需要能夠設置字符串。 話雖如此，我在理解ModelBinding來完成此任務時遇到了問題。 我已經為ModelBinder附加了一個非常基本的設置，但是不知道從哪里可以找到：

/// <summary>
/// Handles binding for the string variables
/// </summary>
public class ActionResultModelBinder : DefaultModelBinder, IModelBinder, ITypedModelBinder
{
    #region Properties

    /// <summary>
    /// Gets the type that this model binder's associated with
    /// </summary>
    /// <value>
    /// The type that this model binder's associated with.
    /// </value>
    public Type AssociatedType
    {
        get
        {
           return typeof(string);
        }
    }

    #endregion Properties

    #region Methods

    /// <summary>
    /// Binds the model by using the specified controller context and binding context.
    /// </summary>
    /// <param name="controllerContext">The context within which the controller operates. The context information includes the controller, HTTP content, request context, and route data.</param>
    /// <param name="bindingContext">The context within which the model is bound. The context includes information such as the model object, model name, model type, property filter, and value provider.</param>
    /// <returns>
    /// The bound object.
    /// </returns>
    /// <exception cref="T:System.ArgumentNullException">The <paramref name="bindingContext "/>parameter is null.</exception>
    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var boundValue = base.BindModel(controllerContext, bindingContext);
        return bindingContext.ModelType == typeof(string);
    }

    /// <summary>
    /// Sets the specified property by using the specified controller context, binding context, and property value.
    /// </summary>
    /// <param name="controllerContext">The context within which the controller operates. The context information includes the controller, HTTP content, request context, and route data.</param>
    /// <param name="bindingContext">The context within which the model is bound. The context includes information such as the model object, model name, model type, property filter, and value provider.</param>
    /// <param name="propertyDescriptor">Describes a property to be set. The descriptor provides information such as the component type, property type, and property value. It also provides methods to get or set the property value.</param>
    /// <param name="value">The value to set for the property.</param>
    protected override void SetProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, object value)
    {
        if (propertyDescriptor.PropertyType == typeof(string))
        {
            var stringVal = value as string;
        }

        base.SetProperty(controllerContext, bindingContext, propertyDescriptor, value);
    }

    #endregion Methods
}

Answer 1

好，讓我解釋一下。

您想綁定一個模型，因此首先需要將模型返回

public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)

這是用於綁定名為FacebookGroupViewModel的模型的自定義綁定程序的示例：

public class FacebookGroupViewModelBinder : IModelBinder
    {
        public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            var model = new FacebookGroupViewModel();
            if(controllerContext.HttpContext.Request.Form.AllKeys.Contains("Friends"))
            {
                var friends = controllerContext.HttpContext.Request.Form["Friends"].Split(',');
                foreach (var friend in friends)
                {
                    model.FacebookFriendIds.Add(friend);
                }


 }
            return model;
        }
    }

在這里您可以看到我從表單中獲取了一個值：

controllerContext.HttpContext.Request.Form["Friends"]

但是您可以從QueryString或其他任何想要的值中獲取值，因為這里有HttpContext。 調試並查看所有必須了解更多信息的屬性。

最后，您需要設置此綁定器，並通過這種方式將其綁定到global.asax中的模型。

ModelBinders.Binders.Add(typeof(FacebookGroupViewModel),new FacebookGroupViewModelBinder());

在應用程序中啟動方法。

然后，只需想象一下，我的控制器就是這樣。

[HttpPost]
public ActionResult PostFriend(FacebookGroupViewModel model)
{
//here your model is binded by your custom model ready to use.
}

工作完成，如果您還有其他疑問，請告訴我。

您實際上不需要的更多信息 ：

 protected override void SetProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, object value)

允許您使用默認的綁定器行為並覆蓋某些屬性，就像您僅使用字符串一樣，但是為此，您需要使用原始的bindModel方法。（例如base.BindModel）