/// <summary>
/// 创建 ContestQueryParameter 类的新实例。
/// </summary>
public ContestQueryParameter()
{
Title = string.Empty;
QueryByTitle = false;
Creator = string.Empty;
QueryByCreator = false;
Status = ContestStatus.Pending;
QueryByStatus = false;
PageQuery = new PageQueryParameter();
EnablePagedQuery = false;
}
/// <summary>
/// 初始化 UserQueryParameter 类的新实例。
/// </summary>
public UserQueryParameter()
{
QueryByOrganization = false;
Organization = string.Empty;
QueryBySex = false;
Sex = UserSex.Male;
QueryByUsergroup = false;
UserGroup = UserGroup.Administrators;
EnablePageQuery = false;
PageQuery = new PageQueryParameter();
}
/// <summary>
/// 创建 SubmissionQueryParameter 类的新实例。
/// </summary>
public SubmissionQueryParameter()
{
ProblemId = string.Empty;
QueryByProblemId = false;
Username = string.Empty;
QueryByUsername = false;
TeamId = 0;
QueryByTeamId = false;
Language = SubmissionLanguage.GnuC;
QueryByLanguage = false;
Verdict = SubmissionVerdict.Accepted;
QueryByVerdict = false;
OrderByDescending = true;
PageQuery = new PageQueryParameter();
EnablePageQuery = false;
}
/// <summary>
/// 在给定的数据集上执行分页。
/// </summary>
/// <typeparam name="T">数据对象类型。</typeparam>
/// <param name="query">原始可查询对象。</param>
/// <param name="parameter">分页参数。</param>
/// <returns>分页后的可查询对象。</returns>
/// <exception cref="ArgumentNullException"/>
/// <exception cref="ArgumentOutOfRangeException"/>
public static IQueryable <T> Page <T>(this IQueryable <T> query, PageQueryParameter parameter)
{
if (query == null)
{
throw new ArgumentNullException(nameof(query));
}
if (parameter.Page <= 0)
{
throw new ArgumentOutOfRangeException(nameof(parameter.Page));
}
if (parameter.ItemsPerPage <= 0)
{
throw new ArgumentOutOfRangeException(nameof(parameter.ItemsPerPage));
}
int totalPages = query.GetPages(parameter.ItemsPerPage);
if (parameter.Page > totalPages)
{
throw new ArgumentOutOfRangeException(nameof(parameter.Page));
}
return(query.Skip(parameter.ItemsPerPage * (parameter.Page - 1)).Take(parameter.ItemsPerPage));
}