Question

如何创建动作过滤器，该过滤器将从Response.Content中删除空值？

只想为一种方法抑制空值

Answer 1

如果您在Formatters.JsonFormatter中使用WebApiConfig.cs，那么

1）：如果您必须在应用程序级别忽略null值，则意味着您所有的api操作

过滤器将为

public class IgnoreNullValuesFilter : ActionFilterAttribute
{
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        actionExecutedContext.ActionContext.RequestContext.Configuration.Formatters.JsonFormatter.SerializerSettings = new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore };
        base.OnActionExecuted(actionExecutedContext);
    }
}

并像

一样将此过滤器添加到您的WebApiConfig.cs

config.Filters.Add(new IgnoreNullValuesFilter());

在添加此过滤器后，您会发现所有api操作都会忽略空值返回数据

您无需为此添加api操作[IgnoreNullValuesFilter]注释，因为我们在WebApiConfig.cs中将其作为全局添加

对于点号2）和3）不要在WebApiConfig.cs

中添加过滤器

2）如果您必须使用操作过滤器忽略特定api操作的空值

然后过滤器将为

public class IgnoreNullValuesFilter : ActionFilterAttribute
{
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        var objectContent = actionExecutedContext.Response.Content as ObjectContent;
        if (objectContent != null)
        {
            var type = objectContent.ObjectType;
            var value = JsonConvert.SerializeObject(objectContent.Value, Newtonsoft.Json.Formatting.Indented, new JsonSerializerSettings
            {
                NullValueHandling = NullValueHandling.Ignore
            });

            objectContent.Value = value;

            //If you want to send your response as strongly type
            JObject jObject = JObject.Parse(value);
            objectContent.Value = jObject;
        }

        base.OnActionExecuted(actionExecutedContext);
    }
}

您的api可以忽略空值

[HttpGet]
[IgnoreNullValuesFilter]
public IHttpActionResult ApiName()
{
    var myObject = new Item { Id = 1, Name = "Matthew", Salary = 25000, Department = null };

    return Ok(myObject);
}

如果要包含空值，则只需从api中删除[IgnoreNullValuesFilter]

3）如果您不想使用任何操作过滤器，则

public class Item
{
    public int Id { get; set; }
    public string Name { get; set; }
    public long Salary { get; set; }
    public string Department { get; set; }
}

您的API将类似于

[HttpGet]
public IHttpActionResult ApiName()
{
    var myObject = new Item { Id = 1, Name = "Matthew", Salary = 25000, Department = null };

    return Json(myObject, new JsonSerializerSettings()
    {
        NullValueHandling = NullValueHandling.Ignore
    });
}

OR

[HttpGet]
public IHttpActionResult ApiName()
{
    var myObject = new Item1 { Id = 1, Name = "Matthew", Salary = 25000, Department = null };

    var jsonIgnoreNullValues = JsonConvert.SerializeObject(myObject, Newtonsoft.Json.Formatting.Indented, new JsonSerializerSettings
        {
          NullValueHandling = NullValueHandling.Ignore
        });

    JObject jObject = JObject.Parse(jsonIgnoreNullValues);

    return Ok(jObject);
}

结果：

在这里您看到Item具有属性department = null被格式化程序忽略的情况。

您可以发送myObject作为所需的任何类型的数据

创建ActionFilter以在WebAPI中排除NULL值

1 个答案: