Question

在我的应用程序中，我使用的是CQRS方法。对于某些查询，我写了IPagedRequest：

public interface IPagedRequest<out TResponse>: IRequest<TResponse> { 
    int Page { get; set; } 
    int PageSize { get; set; } 
}

我的问题是：如何全局设置Page和PageSize属性的默认值？我尝试使用IModelBinder，但是我的代码无法正常工作：

public class PagedRequestBinderProvider : IModelBinderProvider
{
    public IModelBinder GetBinder(ModelBinderProviderContext context)
    {
        if (context == null)
        {
            throw new ArgumentNullException(nameof(context));
        }

        return typeof(IPagedRequest<object>).IsAssignableFrom(context.Metadata.ModelType)
            ? new PagedRequestBinder()
            : null;
    }
}

public class PagedRequestBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        if (bindingContext == null)
        {
            throw new ArgumentNullException(nameof(bindingContext));
        }

        var pagedList = (IPagedRequest<object>) bindingContext.Model;

        if (pagedList.Page == 0) pagedList.Page = 1;
        if (pagedList.PageSize == 0) pagedList.PageSize = 25;

        bindingContext.Result = ModelBindingResult.Success(pagedList);

        return Task.CompletedTask;
    }
}

Answer 1

对于将请求主体绑定到模型，有两种类型，一种是通过Form data从[FromForm]进行绑定，另一种是通过application/json进行[FromBody]的绑定。

对于[FromForm]，它通过IModelBinder绑定模型，对于FromBody，它使用JsonFormatter。

对于操作中的[FromBody]，请尝试以下步骤：

创建自定义json格式化程序

public class CustomJsonInputFormatter : JsonInputFormatter
{
public CustomJsonInputFormatter(
        ILogger logger,
        JsonSerializerSettings serializerSettings,
        ArrayPool<char> charPool,
        ObjectPoolProvider objectPoolProvider,
        MvcOptions options,
        MvcJsonOptions jsonOptions) : base(logger, serializerSettings, charPool, objectPoolProvider, options, jsonOptions)
{
}

public override async Task<InputFormatterResult> ReadRequestBodyAsync(InputFormatterContext context, Encoding encoding)
{
    InputFormatterResult result = await base.ReadRequestBodyAsync(context, encoding);
    var pagedList = (IPagedRequest<object>)result.Model;
    if (pagedList != null)
    {
        if (pagedList.Page == 0) pagedList.Page = 1;
        if (pagedList.PageSize == 0) pagedList.PageSize = 25;
    }
    return result;
}

}

注册json格式器

    services.AddMvc(options => {
        var serviceProvider = services.BuildServiceProvider();
        var customJsonInputFormatter = new CustomJsonInputFormatter(
                 serviceProvider.GetRequiredService<ILoggerFactory>().CreateLogger<CustomJsonInputFormatter>(),
                 serviceProvider.GetRequiredService<IOptions<MvcJsonOptions>>().Value.SerializerSettings,
                 serviceProvider.GetRequiredService<ArrayPool<char>>(),
                 serviceProvider.GetRequiredService<ObjectPoolProvider>(),
                 options,
                 serviceProvider.GetRequiredService<IOptions<MvcJsonOptions>>().Value
            );
        options.InputFormatters.Insert(0, customJsonInputFormatter);

    }).SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

控制器

    [HttpPost]
public ActionResult Test([FromBody]PagedRequest<Product> input)
{
    return Ok(new PagedRequest<Product> {
            Page = 1,
            PageSize = 100
    });
}

ASP.NET Core MVC默认模型值

1 个答案: