C# asp.net核心web api 2中的抽象类模型绑定
我一直在试图找出如何使用.NETCore2WebAPI的自定义模型绑定,但一直未能使其正常工作 我已经阅读了以下几篇文章 在我的例子中,bindingContext.ModelName始终为空。有人能解释为什么会这样吗 下面是示例实现 控制器C# asp.net核心web api 2中的抽象类模型绑定,c#,asp.net-core-2.0,model-binding,C#,Asp.net Core 2.0,Model Binding,我一直在试图找出如何使用.NETCore2WebAPI的自定义模型绑定,但一直未能使其正常工作 我已经阅读了以下几篇文章 在我的例子中,bindingContext.ModelName始终为空。有人能解释为什么会这样吗 下面是示例实现 控制器 public IActionResult SomeAction([ModelBinder(BinderType = typeof(BlahTypeModelBinder))][FromBody]TheBaseClass theBase)
public IActionResult SomeAction([ModelBinder(BinderType = typeof(BlahTypeModelBinder))][FromBody]TheBaseClass theBase)
{
return Ok();
}
模型
public abstract class TheBaseClass
{
public abstract int WhatType { get; }
}
public class A : TheBaseClass
{
public override int WhatType { get { return 1; } }
}
public class B : TheBaseClass
{
public override int WhatType { get { return 2; } }
}
提供者
public class BhalTypeBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
throw new ArgumentNullException(nameof(context));
if (context.Metadata.ModelType == typeof(TheBaseClass))
{
var assembly = typeof(TheBaseClass).Assembly;
var abstractSearchClasses = assembly.GetExportedTypes()
.Where(t => t.BaseType.Equals(typeof(TheBaseClass)))
.Where(t => !t.IsAbstract)
.ToList();
var modelBuilderByType = new Dictionary<Type, Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ComplexTypeModelBinder>();
foreach (var type in abstractSearchClasses)
{
var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
var metadata = context.MetadataProvider.GetMetadataForType(type);
foreach (var property in metadata.Properties)
{
propertyBinders.Add(property, context.CreateBinder(property));
}
modelBuilderByType.Add(type, new Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ComplexTypeModelBinder(propertyBinders));
}
return new BlahTypeModelBinder(modelBuilderByType, context.MetadataProvider);
}
return null;
}
}
公共类BhalTypeBinderProvider:IModelBinderProvider
{
公共IModelBinder GetBinder(ModelBinderProviderContext)
{
if(上下文==null)
抛出新ArgumentNullException(nameof(context));
if(context.Metadata.ModelType==typeof(TheBaseClass))
{
var assembly=typeof(TheBaseClass).assembly;
var abstractSearchClasses=assembly.GetExportedTypes()
其中(t=>t.BaseType.Equals(typeof(TheBaseClass)))
.Where(t=>!t.IsAbstract)
.ToList();
var modelBuilderByType=new Dictionary();
foreach(AbstractSearchClass中的变量类型)
{
var propertyBinders=new Dictionary();
var metadata=context.MetadataProvider.GetMetadataForType(类型);
foreach(metadata.Properties中的var属性)
{
Add(property,context.CreateBinder(property));
}
添加(类型,新的Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ComplexTypeModelBinder(propertyBinders));
}
返回新的BlahTypeModelBinder(modelBuilderByType,context.MetadataProvider);
}
返回null;
}
}
活页夹
public class BlahTypeModelBinder : IModelBinder
{
private readonly IModelMetadataProvider _metadataProvider;
private readonly IDictionary<Type, Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ComplexTypeModelBinder> _binders;
public BlahTypeModelBinder(IDictionary<Type, Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ComplexTypeModelBinder> binders, IModelMetadataProvider metadataProvider)
{
_metadataProvider = metadataProvider;
_binders = binders;
}
public Task BindModelAsync(ModelBindingContext bindingContext)
{
if (bindingContext == null)
throw new ArgumentNullException(nameof(bindingContext));
var modelTypeValue = bindingContext.ValueProvider.GetValue(ModelNames.CreatePropertyModelName(bindingContext.ModelName, "WhatType"));
if (modelTypeValue != null && modelTypeValue.FirstValue != null)
{
Type modelType = Type.GetType(modelTypeValue.FirstValue);
if (this._binders.TryGetValue(modelType, out var modelBinder))
{
ModelBindingContext innerModelBindingContext = DefaultModelBindingContext.CreateBindingContext(
bindingContext.ActionContext,
bindingContext.ValueProvider,
this._metadataProvider.GetMetadataForType(modelType),
null,
bindingContext.ModelName);
/*modelBinder*/
this._binders.First().Value.BindModelAsync(innerModelBindingContext);
bindingContext.Result = innerModelBindingContext.Result;
return Task.CompletedTask;
}
}
//More code
}
}
公共类BlahTypeModelBinder:IModelBinder
{
私有只读IModelMetadataProvider\u metadataProvider;
专用只读IDictionary活页夹;
公共BlahTypeModelBinder(IDictionary Binder、IModelMetadataProvider metadataProvider)
{
_metadataProvider=metadataProvider;
_粘合剂=粘合剂;
}
公共任务BindModelAsync(ModelBindingContext bindingContext)
{
if(bindingContext==null)
抛出新ArgumentNullException(nameof(bindingContext));
var modelTypeValue=bindingContext.ValueProvider.GetValue(ModelNames.CreatePropertyModelName(bindingContext.ModelName,“WhatType”);
if(modelTypeValue!=null&&modelTypeValue.FirstValue!=null)
{
类型modelType=Type.GetType(modelTypeValue.FirstValue);
if(this._binders.TryGetValue(modelType,out var modelBinder))
{
ModelBindingContext innerModelBindingContext=DefaultModelBindingContext.CreateBindingContext(
bindingContext.ActionContext,
bindingContext.ValueProvider,
此._metadataProvider.GetMetadataForType(modelType),
无效的
bindingContext.ModelName);
/*模型装订机*/
这是.u binders.First().Value.bindmodelsync(innerModelBindingContext);
bindingContext.Result=innerModelBindingContext.Result;
返回Task.CompletedTask;
}
}
//更多代码
}
}
链接到的示例使用外部查询字符串参数确定类型。
如果您像这样调用您的操作:SomeAction?WhatType=YourNamespaceName.A
绑定按预期工作
bindingContext.ModelName
为空很好,它将在模型绑定后设置。如果需要,可以在设置bindingContext.Result后进行设置。参数WhatType
来自QueryStringValueProvider
,因此没有前缀是可以的
如何单独基于JSON实现抽象模型绑定
为此,我们需要:
类型
-s的一些反射 public class BlahValueProvider : IValueProvider
{
private readonly string _requestBody;
public BlahValueProvider(string requestBody)
{
_requestBody = requestBody;
}
private const string PROPERTY_NAME = "WhatType";
public bool ContainsPrefix(string prefix)
{
return prefix == PROPERTY_NAME;
}
public ValueProviderResult GetValue(string key)
{
if (key != PROPERTY_NAME)
return ValueProviderResult.None;
// parse json
try
{
var json = JObject.Parse(_requestBody);
return new ValueProviderResult(json.Value<int>("WhatType").ToString());
}
catch (Exception e)
{
// TODO: error handling
throw;
}
}
}
public class BlahValueProviderFactory : IValueProviderFactory
{
public Task CreateValueProviderAsync(ValueProviderFactoryContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
var request = context.ActionContext.HttpContext.Request;
if (request.ContentType == "application/json")
{
return AddValueProviderAsync(context);
}
return Task.CompletedTask;
}
private Task AddValueProviderAsync(ValueProviderFactoryContext context)
{
using (StreamReader sr = new StreamReader(context.ActionContext.HttpContext.Request.Body))
{
string bodyString = sr.ReadToEnd();
context.ValueProviders.Add(new BlahValueProvider(bodyString));
}
return Task.CompletedTask;
}
}
公共类BlahValueProvider:IValueProvider
{
私有只读字符串_requestBody;
公共BlahValueProvider(字符串请求体)
{
_requestBody=requestBody;
}
私有常量字符串属性\u NAME=“WhatType”;
公共bool ContainsPrefix(字符串前缀)
{
返回前缀==属性名称;
}
public ValueProviderResult GetValue(字符串键)
{
如果(键!=属性名称)
返回值ProviderResult.None;
//解析json
尝试
{
var json=JObject.Parse(_requestBody);
返回新的ValueProviderResult(json.Value(“WhatType”).ToString();
}
捕获(例外e)
{
//TODO:错误处理
投掷;
}
}
}
公共类BlahValueProviderFactory:IValueProviderFactory
{
公共任务CreateValueProviderAsync(ValueProviderFactoryContext上下文)
{
if(上下文==null)
{
抛出新ArgumentNullException(nameof(context));
}
var request=context.ActionContext.HttpContext.request;
if(request.ContentType==“应用程序/json”)
{
返回AddValueProviderAsync(上下文);
}
返回Task.CompletedTask;
}
专用任务AddValueProviderAsync(ValueProviderFactoryContext上下文)
{
使用(StreamReader sr=newstreamreader(context.ActionContext.HttpContext.Request.Body))
{
字符串bodyString=sr.ReadToEnd();
Add(新BlahValueProvider(bodyString));
}
返回Task.CompletedTask;
}
}
当然<
public class BlahTypeModelBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext bindingContext)
{
if (bindingContext == null)
throw new ArgumentNullException(nameof(bindingContext));
var json = ExtractRequestJson(bindingContext.ActionContext);
var jObject = Newtonsoft.Json.Linq.JObject.Parse(json);
var whatTypeInt = (int)jObject.SelectToken("WhatType");
if (whatTypeInt == 1)
{
var obj = DeserializeObject<A>(json);
bindingContext.Result = ModelBindingResult.Success(obj);
}
else if (whatTypeInt == 2)
{
var obj = DeserializeObject<B>(json);
bindingContext.Result = ModelBindingResult.Success(obj);
}
else
{
bindingContext.Result = ModelBindingResult.Failed();
return Task.CompletedTask;
}
return Task.CompletedTask;
}
private static string ExtractRequestJson(ActionContext actionContext)
{
var content = actionContext.HttpContext.Request.Body;
return new StreamReader(content).ReadToEnd();
}
private static T DeserializeObject<T>(string json)
{
return Newtonsoft.Json.JsonConvert.DeserializeObject<T>(json, new Newtonsoft.Json.JsonSerializerSettings
{
TypeNameHandling = Newtonsoft.Json.TypeNameHandling.Auto
});
}
}