我假设您的请求数据中有一个属性orderBy
您想要绑定到OrderExpression
using OrderExpression.TryParse
.
让我们假设你的OrderExpression
类如下所示,我在其中提供了一个非常简单的实现TryParse
method:
public class OrderExpression
{
public string RawValue { get; set; }
public static bool TryParse(string value, out OrderExpression expr)
{
expr = new OrderExpression { RawValue = value };
return true;
}
}
然后您可以创建一个模型绑定器,它基本上获取原始字符串值并调用OrderExpression.TryParse
:
public class OrderExpressionBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext bindingContext)
{
var values = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
if (values.Length == 0) return Task.CompletedTask;
// Attempt to parse
var stringValue = values.FirstValue;
OrderExpression expression;
if (OrderExpression.TryParse(stringValue, out expression))
{
bindingContext.ModelState.SetModelValue(bindingContext.ModelName, expression, stringValue);
bindingContext.Result = ModelBindingResult.Success(expression);
}
return Task.CompletedTask;
}
}
您还需要一个新的模型活页夹提供程序,它仅返回您的新活页夹OrderExpression
type:
public class OrderExpressionBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
return context.Metadata.ModelType == typeof(OrderExpression) ? new OrderExpressionBinder() : null;
}
}
// It should be registered in your Startup class, adding it to the ModelBinderProviders collection:
services.AddMvc(opts => {
opts.ModelBinderProviders.Insert(0, new OrderExpressionBinderProvider());
});
完成此操作后,您将能够绑定OrderExpression
控制器动作的参数。类似于以下示例:
[HttpPost]
public IActionResult Products([FromBody]OrderExpression orderBy)
{
return Ok();
}
$.ajax({
method: 'POST',
dataType: 'json',
url: '/home/products',
data: {orderby: 'my orderby expression'}
});
然而,您还需要做一些其他事情才能发送 json 并将其绑定到复杂的模型,例如GetProductsModel
其内部包含一个OrderExpression
。我正在谈论这样一个场景:
[HttpPost]
public IActionResult Products([FromBody]GetProductsModel model)
{
return Ok();
}
public class GetProductsModel
{
public OrderExpression OrderBy { get; set; }
}
$.ajax({
method: 'POST',
dataType: 'json',
contentType: 'application/json; charset=utf-8',
url: '/home/products',
data: JSON.stringify({orderby: 'my orderby expression'})
});
在这种情况下,ASP.Net Core 将仅使用 Newtonsoft.Json 作为 InputFormatter,并将接收到的 json 转换为GetProductsModel
模型,而不尝试使用新的OrderExpressionBinderProvider
对于内部属性。
幸运的是,您还可以告诉 Newtonsoft.Json 如何格式化属性OrderExpression
通过创建 JsonConverter 键入:
public class OrderExpressionJsonConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType == typeof(OrderExpression);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var stringValue = reader.Value?.ToString();
OrderExpression expression;
if (OrderExpression.TryParse(stringValue, out expression))
{
return expression;
}
return null;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
应该在您的 Startup 类中注册:
services.AddMvc(opts => {
opts.ModelBinderProviders.Insert(0, new OrderExpressionBinderProvider());
}).AddJsonOptions(opts => {
opts.SerializerSettings.Converters.Add(new OrderExpressionJsonConverter());
});
现在您终于能够处理这两种情况了:)