/// <summary>
/// Appends the paging instructions.
/// </summary>
/// <param name="options">The paging options.</param>
/// <param name="sb">The target string builder.</param>
private void AppendPaging(PagingOptions options, StringBuilder sb)
{
sb.Append("LIMIT ")
.AppendLine(
options.PageSize.ToString(CultureInfo.InvariantCulture))
.Append("OFFSET ")
.Append(options.GetSkipCount())
.AppendLine();
}
/// <summary>
/// Appends the paging instructions.
/// </summary>
/// <param name="options">The paging options.</param>
/// <param name="sb">The target string builder.</param>
protected override void AppendPaging(PagingOptions options,
StringBuilder sb)
{
sb.Append("OFFSET ")
.Append(options.GetSkipCount())
.AppendLine(" ROWS")
.Append("FETCH NEXT ")
.Append(options.PageSize)
.AppendLine(" ROWS ONLY");
}
/// <summary>
/// Selects page from a collection.
/// </summary>
public static async Task <Page <TEntity> > ToPageAsync <TEntity>(this IQueryable <TEntity> query, PagingOptions options)
{
if (query == null)
{
throw new ArgumentNullException(nameof(query));
}
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
var result = query;
var skipCount = options.GetSkipCount();
if (skipCount > 0)
{
result = result.Skip(skipCount);
}
var takeCount = options.GetTakeCount();
var data = takeCount <= 0 ? new TEntity[0] : await result.Take(takeCount).ToArrayAsync();
var total = -1;
var overflow = false;
if (options.AcquireTotal)
{
if (options.MaximumCount != null)
{
var max = options.MaximumCount.Value * options.Size - options.Offset;
total = options.Offset + await query.Take(max + 1).CountAsync();
if (total > max)
{
overflow = true;
total = max;
}
}
else
{
total = options.Offset + await query.CountAsync();
}
}
return(new Page <TEntity>(
data,
options.Number,
options.Size,
total,
overflow
));
}
