Pagination In WebAPI | 易学教程

问题

Currently I have following way of providing pagination for every entity/resource for a set of APIs:

public IHttpActionResult GetPageUsers(int startindex, int size, string sortby = "Username", string order = "DESC")
{
    if (!order.Equals("ASC") && !order.Equals("DESC"))
        return BadRequest("Order Has To Be DESC or ASC");

    if (!new string[] { "username", "name" }.Contains(sortby.ToLower()))
        return BadRequest("Not A Valid Sorting Column");

    return Ok(new
    {
        records = Mapper.Map<List<User>, List<HomeBook.API.Models.User.UserDTO>>(
            db.Users.OrderBy(sortby + " " + order).Skip(startindex).Take(size).ToList()
        ),
        total = db.Users.Count()
    });
}

But I would like to move the validation logic to Model so that I can reply back with ModelState errors from one of my Action filters and the request would not even need to get inside the controller.

But I cannot also change the action signature to expect an object parameter to what I have already otherwise, I get multiple action error.

Basically, what I am asking is how I can remove validation logic from here to somewhere else so that the request does not even need to get inside the action. I would really appreciate some insight on this problem or even pagination in WebAPIs in general

回答1:

You could define an action filter attribute to perform the validation:

public class ValidatePagingAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        string order = (string) actionContext.ActionArguments["order"];
        string sortBy = (string) actionContext.ActionArguments["sortby"];

        var states = new ModelStateDictionary();
        if(!order.Equals("ASC") && !order.Equals("DESC"))
        {
            states.AddModelError("order", "Order has to be DESC or ASC");
        }

        if (!new[] { "username", "name" }.Contains(sortBy.ToLower()))
        {
            states.AddModelError("sortby", "Not A Valid Sorting Column");
        }

        if(states.Any())
        {
            actionContext.Response = actionContext.Request.CreateErrorResponse(HttpStatusCode.BadRequest, states);
        }
    }
}

And then use it like so:

[ValidatePaging]
public IHttpActionResult GetPageUsers(int startindex, int size, string sortby = "Username", string order = "DESC")
{
    // stuff
}

Also, have a look at http://bitoftech.net/2013/11/25/implement-resources-pagination-asp-net-web-api on how to implement paging in web api.

来源：https://stackoverflow.com/questions/26711756/pagination-in-webapi

标签

rest

asp.net-web-api

pagination