我已经成功(可能没有优雅地)创建了一个模型绑定器,它将在post上绑定一个接口列表。每个接口都有单独的属性,有些具有另一个接口的嵌套List。接口列表在视图中正确显示,嵌套列表项也是如此。在帖子上一切正常,调用自定义模型绑定器并构建正确的类型。我遇到的问题是,如果嵌套的接口列表没有要显示的项目,则在回发后,模型绑定器将不会构建该对象以及之后的任何对象。
我正在使用剃刀页面及其各自的页面模型。我在pagemodel中使用了[BindProperty]
注释。
使用具体实现修剪接口:我已经删除了类并省略了不必要的代码...
public interface IQuestion
{
Guid Number{ get; set; }
string Text{ get; set; }
List<IAnswer> AnswerList{ get; set; }
..
}
public interface IAnswer
{
string Label { get; set; }
string Tag { get; set; }
..
}
public class MetaQuestion: IQuestion
{
public int Number{ get; set; }
public string Text{ get; set; }
public List<IAnswer> AnswerList{ get; set; }
..
}
public class Answer: IAnswer
{
public string Label { get; set; }
public string Tag { get; set; }
..
}
public class TestListModel : PageModel
{
private readonly IDbSession _dbSession;
[BindProperty]
public List<IQuestion> Questions { get; set; }
public TestListModel(IDbSession dbSession)
{
_dbSession= dbSession;
}
public async Task OnGetAsync()
{
//just to demonstrate where the data is comming from
var allQuestions = await _dbSession.GetAsync<Questions>();
if (allQuestions == null)
{
return NotFound($"Unable to load questions.");
}
else
{
Questions = allQuestions;
}
}
public async Task<IActionResult> OnPostAsync()
{
//do something random with the data from the post back
var question = Questions.FirstOrDefault();
..
return Page();
}
}
这是生成的代码的html不起作用。其中一个问题项目,特别是列表中的第二个项目,在Answers
中没有任何AnswerList
。
我们可以看到,列表中的第二个问题在AnswerList中没有'Answer'项。这意味着在回发后,我只收到列表中的第一个问题。如果我从列表中删除第二个问题,那么我会回答所有问题。
为了简洁起见,我删除了所有样式,类和div。
问题1:
<input id="Questions_0__Number" name="Questions[0].Number" type="text" value="sq1">
<input id="Questions_0__Text" name="Questions[0].Text" type="text" value="Are you:">
<input name="Questions[0].TargetTypeName" type="hidden" value="Core.Model.MetaData.MetaQuestion, Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
<input data-val="true" data-val-required="The Tag field is required." id="Questions_0__AnswerList_0__Tag" name="Questions[0].AnswerList[0].Tag" type="text" value="1">
<input id="Questions_0__AnswerList_0__Label" name="Questions[0].AnswerList[0].Label" type="text" value="Male">
<input id="Questions_0__AnswerList_0__TargetTypeName" name="Questions[0].AnswerList[0].TargetTypeName" type="hidden" value="Core.Common.Implementations.Answer, Core.Common, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
问题2:
<input id="Questions_1__Number" name="Questions[1].Number" type="text" value="sq1">
<input id="Questions_1__Text" name="Questions[1].Text" type="text" value="Are you:">
<input name="Questions[1].TargetTypeName" type="hidden" value="Core.Model.MetaData.MetaQuestion, Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
问题2之后的其余问题与问题1类似。
我知道这不是最好的方法,包括TargetTypeName
并不理想。真的没有太多可以找到帮助解决这个问题。对于ASP web dev,我是新手。
public class IQuestionModelBinder : IModelBinder
{
private readonly IDictionary<Type, ComplexTypeModelBinder> modelBuilderByType;
private readonly IModelMetadataProvider modelMetadataProvider;
public IQuestionModelBinder(IDictionary<Type, ComplexTypeModelBinder> modelBuilderByType, IModelMetadataProvider modelMetadataProvider)
{
this.modelBuilderByType = modelBuilderByType ?? throw new ArgumentNullException(nameof(modelBuilderByType));
this.modelMetadataProvider = modelMetadataProvider ?? throw new ArgumentNullException(nameof(modelMetadataProvider));
}
public Task BindModelAsync(ModelBindingContext bindingContext)
{
var str = ModelNames.CreatePropertyModelName(bindingContext.ModelName, "TargetTypeName");
var modelTypeValue = bindingContext.ValueProvider.GetValue(ModelNames.CreatePropertyModelName(bindingContext.ModelName, "TargetTypeName"));
if (modelTypeValue != null && modelTypeValue.FirstValue != null)
{
Type modelType = Type.GetType(modelTypeValue.FirstValue);
if (this.modelBuilderByType.TryGetValue(modelType, out var modelBinder))
{
ModelBindingContext innerModelBindingContext = DefaultModelBindingContext.CreateBindingContext(
bindingContext.ActionContext,
bindingContext.ValueProvider,
this.modelMetadataProvider.GetMetadataForType(modelType),
null,
bindingContext.ModelName);
modelBinder.BindModelAsync(innerModelBindingContext);
bindingContext.Result = innerModelBindingContext.Result;
return Task.CompletedTask;
}
}
bindingContext.Result = ModelBindingResult.Failed();
return Task.CompletedTask;
}
}
提供者:
public class IQuestionModelBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.ModelType == typeof(IQuestion))
{
var assembly = typeof(IQuestion).Assembly;
var metaquestionClasses = assembly.GetExportedTypes()
.Where(t => !t.IsInterface || !t.IsAbstract)
.Where(t => t.BaseType.Equals(typeof(IQuestion)))
.ToList();
var modelBuilderByType = new Dictionary<Type, ComplexTypeModelBinder>();
foreach (var type in metaquestionClasses)
{
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 ComplexTypeModelBinder(propertyBinders: propertyBinders));
}
return new IMetaQuestionModelBinder(modelBuilderByType, context.MetadataProvider);
}
return null;
}
类似于IAnswer接口(可能重构为没有2个绑定器):
public class IAnswerModelBinder : IModelBinder
{
private readonly IDictionary<Type, ComplexTypeModelBinder> modelBuilderByType;
private readonly IModelMetadataProvider modelMetadataProvider;
public IAnswerModelBinder(IDictionary<Type, ComplexTypeModelBinder> modelBuilderByType, IModelMetadataProvider modelMetadataProvider)
{
this.modelBuilderByType = modelBuilderByType ?? throw new ArgumentNullException(nameof(modelBuilderByType));
this.modelMetadataProvider = modelMetadataProvider ?? throw new ArgumentNullException(nameof(modelMetadataProvider));
}
public Task BindModelAsync(ModelBindingContext bindingContext)
{
var str = ModelNames.CreatePropertyModelName(bindingContext.ModelName, "TargetTypeName");
var modelTypeValue = bindingContext.ValueProvider.GetValue(ModelNames.CreatePropertyModelName(bindingContext.ModelName, "TargetTypeName"));
if (modelTypeValue != null && modelTypeValue.FirstValue != null)
{
Type modelType = Type.GetType(modelTypeValue.FirstValue);
if (this.modelBuilderByType.TryGetValue(modelType, out var modelBinder))
{
ModelBindingContext innerModelBindingContext = DefaultModelBindingContext.CreateBindingContext(
bindingContext.ActionContext,
bindingContext.ValueProvider,
this.modelMetadataProvider.GetMetadataForType(modelType),
null,
bindingContext.ModelName);
modelBinder.BindModelAsync(innerModelBindingContext);
bindingContext.Result = innerModelBindingContext.Result;
return Task.CompletedTask;
}
}
bindingContext.Result = ModelBindingResult.Failed();
return Task.CompletedTask;
}
}
提供者:
public class IAnswerModelBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.ModelType == typeof(IAnswer))
{
var exportedTypes = typeof(IAnswer).Assembly.GetExportedTypes();
var metaquestionClasses = exportedTypes
.Where(y => y.BaseType != null && typeof(IAnswer).IsAssignableFrom(y) && !y.IsInterface)
.ToList();
var modelBuilderByType = new Dictionary<Type, ComplexTypeModelBinder>();
foreach (var type in metaquestionClasses)
{
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 ComplexTypeModelBinder(propertyBinders: propertyBinders));
}
return new IAnswerModelBinder(modelBuilderByType, context.MetadataProvider);
}
return null;
}
这些都注册如下:
services.AddMvc(
options =>
{
// add custom binder to beginning of collection (serves IMetaquestion binding)
options.ModelBinderProviders.Insert(0, new IMetaQuestionModelBinderProvider());
options.ModelBinderProviders.Insert(0, new IAnswerModelBinderProvider());
})
.SetCompatibilityVersion(CompatibilityVersion.Version_2_2));
我试图提供尽可能多的信息。
我已经在这几天了,最终除了这一个案例之外,还有所有绑定工作。
有助于实现这一目标的SO帖子:
我知道模型绑定器使用递归,这使我相信发生了一些事情,一旦它击中没有Question
值的AnswerList
就停止执行。
我唯一注意到的是html中的AnswerList
Tag
属性将data-val
设置为true,data-val-required
也是如此。
<input data-val="true" data-val-required="The Tag field is required." id="Questions_0__AnswerList_0__Tag" name="Questions[0].AnswerList[0].Tag" type="text" value="1"
我不知道为什么会这样。我没有明确地说明这一点。该类位于不同的命名空间中,我们宁愿不在整个类中应用数据注释。
这可能是什么打破了绑定,因为它期待一个值,但我不能确定。
这个问题是正常行为吗?如果是这样,解决方案是什么?
我将继续回答我自己的问题。这解决了这个问题。这是我的编辑器模板看起来像Question
@model MetaQuestion
<div class="card card form-group" style="margin-top:10px;">
<div class="card-header">
<strong>
@Html.TextBoxFor(x => x.Number, new { @class = "form-control bg-light", @readonly = "readonly", @style = "border:0px;" })
</strong>
</div>
<div class="card-body text-black-50">
<h6 class="card-title mb-2 text-muted">
@Html.TextBoxFor(x => x.Text, new { @class = "form-control", @readonly = "readonly", @style = "background-color:white; border:0px;" })
</h6>
@for (int i = 0; i < Model.AnswerList.Count; i++)
{
<div class="row">
<div class="col-1">
@Html.TextBoxFor(x => x.AnswerList[i].PreCode, new { @class = "form-control", @readonly = "readonly", @style = "background-color:white; border:0px;" })
</div>
<div class="col">
@Html.TextBoxFor(x => x.AnswerList[i].Label, new { @class = "form-control", @readonly = "readonly", @style = "background-color:white; border:0px;" })
</div>
<div class="col-1">
@Html.HiddenFor(x => x.AnswerList[i].TargetTypeName)
</div>
<div class="col-1">
<input name="@(ViewData.TemplateInfo.HtmlFieldPrefix + ".TargetTypeName")" type="hidden" value="@this.Model.GetType().AssemblyQualifiedName" />
</div>
</div>
}
</div>
</div>
接近尾声你可以看到有2列包括HiddenFor
助手。我正在使用这些来识别接口的类型,它允许我的问题中提到的自定义模型绑定器选择相关类型。
对我来说不明显的是,当'问题'没有'答案'时,它忽略了for循环内外的所有值。因此,自定义绑定器永远无法找到Question
的类型,因为数据完全丢失了。
我已经开始重新订购解决了这个问题的Html.HiddenFor
助手。我的编辑器现在看起来如下:
@model MetaQuestion
<div class="card card form-group" style="margin-top:10px;">
<div class="card-header">
<input name="@(ViewData.TemplateInfo.HtmlFieldPrefix + ".TargetTypeName")" type="hidden" value="@this.Model.GetType().AssemblyQualifiedName" />
<strong>
@Html.TextBoxFor(x => x.Number, new { @class = "form-control bg-light", @readonly = "readonly", @style = "border:0px;" })
</strong>
</div>
<div class="card-body text-black-50">
<h6 class="card-title mb-2 text-muted">
@Html.TextBoxFor(x => x.Text, new { @class = "form-control", @readonly = "readonly", @style = "background-color:white; border:0px;" })
</h6>
@for (int i = 0; i < Model.AnswerList.Count; i++)
{
@Html.HiddenFor(x => x.AnswerList[i].TargetTypeName)
<div class="row">
<div class="col-1">
@Html.TextBoxFor(x => x.AnswerList[i].PreCode, new { @class = "form-control", @readonly = "readonly", @style = "background-color:white; border:0px;" })
</div>
<div class="col">
@Html.TextBoxFor(x => x.AnswerList[i].Label, new { @class = "form-control", @readonly = "readonly", @style = "background-color:white; border:0px;" })
</div>
</div>
}
</div>
</div>
预先放置它确保它始终存在。这可能不是处理整个情况的最佳方式,但至少它解决了这个问题。