我最终使用的方法是创建一个我在全球注册的自定义过滤器。过滤器检查所有请求参数RequiredAttribute
。如果找到该属性,则检查参数是否随请求一起传递(非空),如果为空,则返回状态代码 400。我还在过滤器中添加了一个缓存来存储每个请求所需的参数,以避免对未来调用的反射命中。我惊喜地发现这也适用于值类型,因为操作上下文将参数存储为对象。
编辑 - 根据 tecfield 的评论更新解决方案
public class RequiredParametersFilter : ActionFilterAttribute
{
// Cache used to store the required parameters for each request based on the
// request's http method and local path.
private readonly ConcurrentDictionary<Tuple<HttpMethod, string>, List<string>> _Cache =
new ConcurrentDictionary<Tuple<HttpMethod, string>, List<string>>();
public override void OnActionExecuting(HttpActionContext actionContext)
{
// Get the request's required parameters.
List<string> requiredParameters = this.GetRequiredParameters(actionContext);
// If the required parameters are valid then continue with the request.
// Otherwise, return status code 400.
if(this.ValidateParameters(actionContext, requiredParameters))
{
base.OnActionExecuting(actionContext);
}
else
{
throw new HttpResponseException(HttpStatusCode.BadRequest);
}
}
private bool ValidateParameters(HttpActionContext actionContext, List<string> requiredParameters)
{
// If the list of required parameters is null or containst no parameters
// then there is nothing to validate.
// Return true.
if (requiredParameters == null || requiredParameters.Count == 0)
{
return true;
}
// Attempt to find at least one required parameter that is null.
bool hasNullParameter =
actionContext
.ActionArguments
.Any(a => requiredParameters.Contains(a.Key) && a.Value == null);
// If a null required paramter was found then return false.
// Otherwise, return true.
return !hasNullParameter;
}
private List<string> GetRequiredParameters(HttpActionContext actionContext)
{
// Instantiate a list of strings to store the required parameters.
List<string> result = null;
// Instantiate a tuple using the request's http method and the local path.
// This will be used to add/lookup the required parameters in the cache.
Tuple<HttpMethod, string> request =
new Tuple<HttpMethod, string>(
actionContext.Request.Method,
actionContext.Request.RequestUri.LocalPath);
// Attempt to find the required parameters in the cache.
if (!this._Cache.TryGetValue(request, out result))
{
// If the required parameters were not found in the cache then get all
// parameters decorated with the 'RequiredAttribute' from the action context.
result =
actionContext
.ActionDescriptor
.GetParameters()
.Where(p => p.GetCustomAttributes<RequiredAttribute>().Any())
.Select(p => p.ParameterName)
.ToList();
// Add the required parameters to the cache.
this._Cache.TryAdd(request, result);
}
// Return the required parameters.
return result;
}
}