public static JsonApiPagination ExtractPagination(this HttpRequestMessage request)
{
var hasPageNumberParam = false;
var hasPageSizeParam = false;
var pageNumber = 0;
var pageSize = DefaultPageSize;
foreach (var kvp in request.GetQueryNameValuePairs())
{
if (kvp.Key == PageNumberQueryParam)
{
hasPageNumberParam = true;
if (!int.TryParse(kvp.Value, out pageNumber))
{
throw new Exception("Page number must be a positive integer.");
}
}
else if (kvp.Key == PageSizeQueryParam)
{
hasPageSizeParam = true;
if (!int.TryParse(kvp.Value, out pageSize))
{
throw new Exception("Page size must be a positive integer.");
}
}
}
if (!hasPageNumberParam && !hasPageSizeParam)
{
return(null);
}
if ((hasPageNumberParam && !hasPageSizeParam))
{
throw new Exception(string.Format("In order for paging to work properly, if either {0} or {1} is set, both must be.",
PageNumberQueryParam, PageSizeQueryParam));
}
if ((!hasPageNumberParam && hasPageSizeParam))
{
throw new Exception(string.Format("In order for paging to work properly, if either {0} or {1} is set, both must be.",
PageNumberQueryParam, PageSizeQueryParam));
}
if (pageNumber < 0)
{
throw new Exception("Page number must not be negative.");
}
if (pageSize <= 0)
{
throw new Exception("Page size must be greater than or equal to 1.");
}
JsonApiPagination pagination = new JsonApiPagination();
pagination.PageNumber = pageNumber;
pagination.PageSize = pageSize;
return(pagination);
}
public static IQueryable <T> GeneratePagination <T>(this IQueryable <T> query, JsonApiPagination pagination)
{
if (pagination != null)
{
query = query.Skip(pagination.PageNumber * pagination.PageSize).Take(pagination.PageSize);
}
return(query);
}