Asp.net Vnext ModelBinding

Model Binding

本文已经同步到《Asp.net Vnext 系列教程 》中]

Model binding(绑定)简单来说就是通过遍历ValueProvider(值提供者)获取的数据对Action参数进行赋值.

在学习本篇教程，应对model binding有基础了解。

DefaultPropertyBindingPredicateProvider

DefaultPropertyBindingPredicateProvider：提供一种基于表达式的方法来提供包括的属性。

public class DefaultPropertyBindingPredicateProvider<TModel> : IPropertyBindingPredicateProvider where TModel : class
{
public DefaultPropertyBindingPredicateProvider();

public virtual string Prefix { get; }
public virtual Func<ModelBindingContext, string, bool> PropertyFilter { get; }

public virtual IEnumerable<Expression<Func<TModel, object>>> PropertyIncludeExpressions { get; }
}

这个类有三个属性：

Prefix 表示前缀名

PropertyFilter ：属性过滤

PropertyIncludeExpressions ：属性包括表达式
来看下怎么用实例代码

private class ExcludeUserPropertiesAtParameter : DefaultPropertyBindingPredicateProvider<User>
{
Func<ModelBindingContext, string, bool> _defaultFilter1 =
(context, propertyName) => false;

public   ExcludeUserPropertiesAtParameter()
{

}
public override string Prefix
{
get
{
return "user";
}
}

public override IEnumerable<Expression<Func<User, object>>> PropertyIncludeExpressions
{

get
{

yield return m => m.RegisterationMonth;
yield return m => m.UserName;
}
}
}

控制器

public class BindAttributeController : Controller
{
public User EchoUser([Bind(typeof(ExcludeUserPropertiesAtParameter))] User user)
{
return user;
}

User实体

public class User
{
[Required]
public int Id { get; set; }
public int Key { get; set; }

[Required]
public string RegisterationMonth { get; set; }
public string UserName { get; set; }

public Address Address { get; set; }
}

Prefix 前缀名是user，也就是说请求id必需加上user作为前缀

PropertyIncludeExpressions：属性包括：

get

{ yield return m => m.RegisterationMonth; yield return m => m.UserName; }

表示：支队这个属性进行赋值。

我们来看看PropertyFilter作用

private class ExcludeUserPropertiesAtParameter : DefaultPropertyBindingPredicateProvider<User>
{
Func<ModelBindingContext, string, bool> _defaultFilter1 =
(context, propertyName) => false;

public   ExcludeUserPropertiesAtParameter()
{

}
public override string Prefix
{
get
{
return "user";
}
}
public override Func<ModelBindingContext, string, bool> PropertyFilter
{
get
{
return _defaultFilter1;
}
}

}

_defaultFilter1 表达式一直返回false

全部没有赋值，

PropertyFilter：

PropertyIncludeExpressions等于null propertyFilter 将默认返回true.

FromRoute
FromQuery
FromForm
FromBody
FromHeader
FromServices

这是属性表示绑定的值从何获取

[Route("/FromAttributes/[Action]/{HomeAddress.Street}/{HomeAddress.State}/{HomeAddress.Zip}", Name = "yangwen")]
public User_FromForm GetUser([FromRoute] Address homeAddress,

[FromQuery] Address shippingAddress)
{

return new User_FromForm
{
HomeAddress = homeAddress,

ShippingAddress = shippingAddress
};
}

控制器

FromRoute:从路由绑定

FromQuery:参数绑定

控制器

[Route("/FromAttributes1",Name ="yangwen1")]
public void GetUser1( [FromForm] Address officeAddress  )
{

}

视图

@model ModelBindingWebSite.Models.Address
@using (Html.BeginRouteForm("yangwen1", FormMethod.Post))
{

@Html.EditorForModel();
<input type="submit" value="Submit">

}

FromForm：表单绑定

控制器

[HttpGet("BindToModelWithInitializedValue")]
public object BindToModelWithInitializedValue(BlogPostWithInitializedValue blogPost)
{
return new Result()
{
HeaderValue = blogPost.Host,
HeaderValues = blogPost.Tags,
ModelStateErrors = ModelState.Where(kvp => kvp.Value.Errors.Count > 0).Select(kvp => kvp.Key).ToArray(),
};
}

public class BlogPostWithInitializedValue
{
[Required]
[FromHeader]
public string Host { get; set; } = "How to Make Soup";

[FromHeader]
public string[] Tags { get; set; } = new string[] { "Cooking" };

public string Author { get; set; }
}

FromHeader:Header绑定

控制器

public int Add(int left, int right, [FromServices] ICalculator calculator)
{
return calculator.Operation('+', left, right);
}

IOC

services.AddSingleton<ICalculator, DefaultCalculator>();

FromServices:绑定IOC

FromBody

public void Post([FromBody]Person p)

POST http://localhost:10725/api/values?name=b&age=2HTTP/1.1
Content-Type: application/json
Host: localhost:10725
Content-Length: 30

{“Name” : “John”, “Age” : 24 }

IModelMetadataProvider

Model元数据提供者

public class AdditionalValuesMetadataProvider : IDisplayMetadataProvider
{

private static Guid _guid = new Guid("7d6d0de2-8d59-49ac-99cc-881423b75a76");

public void GetDisplayMetadata(DisplayMetadataProviderContext context)
{

//添加附加值
context.DisplayMetadata.AdditionalValues.Add("key1", _guid);
context.DisplayMetadata.AdditionalValues.Add("key2", "value2");

}
}

启动类

services.AddMvc()
.Configure<MvcOptions>(m =>
{

m.ModelMetadataDetailsProviders.Add(new AdditionalValuesMetadataProvider());
});

控制器

public IReadOnlyDictionary<object, object> GetAdditionalValues([FromServices] IModelMetadataProvider provider)
{
var metadata = provider.GetMetadataForType(typeof(LargeModelWithValidation));
//输出附加值
return metadata.AdditionalValues;
}

IModelBinder

模型绑定

private class ProductModelBinder : IModelBinder
{
public async Task<ModelBindingResult> BindModelAsync(ModelBindingContext bindingContext)
{
if (typeof(Product).IsAssignableFrom(bindingContext.ModelType))
{
//实例
var model = (Product)Activator.CreateInstance(bindingContext.ModelType);

model.BinderType = GetType();

var key =
string.IsNullOrEmpty(bindingContext.ModelName) ?
"productId" :
bindingContext.ModelName + "." + "productId";

//获取值
var value = await bindingContext.ValueProvider.GetValueAsync(key);
model.ProductId = (int)value.ConvertTo(typeof(int));

return new ModelBindingResult(model, key, true);
}

return null;
}
}

控制器

public string GetBinderType_UseModelBinder(
[ModelBinder(BinderType = typeof(ProductModelBinder))] Product model)
{
return model.BinderType.FullName;
}