/// <summary>
/// Initializes a new instance of the <see cref="PageNumberAndItemNumbers"/> struct.
/// </summary>
/// <param name="pageNumber">
/// Initial value for the <see cref="PageNumber"/> field.
/// </param>
/// <param name="pageSize">
/// The <see cref="PageNumberAndSize.Size"/>
/// of each page in a "paged" collection.
/// </param>
/// <param name="totalItems">
/// The total number of items in a "paged" collection.
/// </param>
/// <param name="isLastPage">
/// Optional signal for setting the <see cref="LastItemNumber"/>
/// value, whether to calculate if <paramref name="pageNumber"/>
/// is the last page or to use this value.
/// </param>
internal PageNumberAndItemNumbers(
int pageNumber, byte pageSize, int totalItems, bool?isLastPage = null)
{
Contract.Requires <ArgumentOutOfRangeException>(
pageNumber >= PageNumberAndSize.FirstPageNumber,
"An ordinal page number is not a zero-based index. The number must be at least one.");
Contract.Requires <ArgumentOutOfRangeException>(
totalItems >= 0, "The number of items in the list must not be negative!");
if (pageSize >= PageNumberAndSize.MinimumPageSize && (totalItems > 0))
{
// A page of fixed size which has items.
this.PageNumber = pageNumber;
this.LastItemNumber = pageNumber * pageSize;
this.FirstItemNumber = this.LastItemNumber - pageSize + 1;
// Determine whether this is the last page,
// either by a parameter value or by calculation.
if ((isLastPage.HasValue && isLastPage.Value) ||
(PagingInfoCalculator.CalculateTotalPages(pageSize, totalItems) == this.PageNumber))
{
// If is the last page, replace the
// calculated LastItemNumber with
// the totalItems value.
this.LastItemNumber = totalItems;
}
}
else
{
// An unbounded or empty page.
this.PageNumber = PageNumberAndSize.FirstPageNumber;
this.FirstItemNumber = totalItems > 0 ? 1 : 0;
this.LastItemNumber = totalItems;
}
}
/// <summary>
/// Initializes a new instance of the <see cref="PagingInfo"/> struct
/// upon deserialization of another <see cref="PagingInfo"/> which
/// this one replaces, used for lazy initialization by the internal
/// <see cref="Calculator"/> property.
/// </summary>
/// <param name="calculator">
/// A <see cref="PagingInfoCalculator"/> value initialized from
/// the <see cref="CurrentPage"/> and <see cref="TotalItems"/>
/// values of a <see cref="PagingInfo"/> value to be replaced
/// by this new instance. To understand how this works,
/// refer to the <see cref="Calculator"/> property.
/// </param>
private PagingInfo(PagingInfoCalculator calculator)
{
this.CurrentPage = calculator.CurrentPage;
this.TotalItems = calculator.TotalItems;
this.calculator = calculator;
this.calculateAllPagesAndItemNumbers = calculator.IncludeAllPagesAndItemNumbers;
}
public IReadOnlyList <PageNumberAndItemNumbers> AllPagesAndItemNumbers()
{
// The value may have already been initialized...
return(this.AllPages ?? (this.CurrentPage.HasValue
? PagingInfoCalculator.AllPagesAndItemNumbers(this)
: new PageNumberAndItemNumbers[0]));
}
/// <summary>
/// Calculates the full set of page numbers and item
/// numbers from given <paramref name="pageSize"/>
/// and <paramref name="totalItems"/> values.
/// </summary>
/// <param name="pageSize">
/// The <see cref="PageNumberAndSize.Size"/>
/// of each page in a "paged" collection.
/// </param>
/// <param name="totalItems">
/// The total number of items in a "paged" collection.
/// </param>
/// <returns>
/// The full set of page numbers and item numbers.
/// </returns>
/// <remarks>
/// Relays to the internal <see cref="PagingInfoCalculator.AllPagesAndItemNumbers(byte,int)"/>
/// method of <see cref="PagingInfoCalculator"/>.
/// </remarks>
public static IReadOnlyList <PageNumberAndItemNumbers> Calculate(
byte pageSize, int totalItems)
{
// Zero as page size is acceptable,
// indicating a single "unbounded" page.
Contract.Requires <ArgumentOutOfRangeException>(
totalItems >= 0, "The number of items in the list must not be negative!");
return(PagingInfoCalculator.AllPagesAndItemNumbers(pageSize, totalItems));
}
public void CalculatesCorrectTotalPages()
{
Assert.Throws <ArgumentOutOfRangeException>(
() => PagingInfoCalculator.CalculateTotalPages(10, 0));
Assert.Throws <ArgumentOutOfRangeException>(
() => PagingInfoCalculator.CalculateTotalPages(0, 1138));
Assert.AreEqual(1, PagingInfoCalculator.CalculateTotalPages(10, 1));
Assert.AreEqual(1, PagingInfoCalculator.CalculateTotalPages(10, 10));
Assert.AreEqual(2, PagingInfoCalculator.CalculateTotalPages(10, 11));
Assert.AreEqual(2, PagingInfoCalculator.CalculateTotalPages(10, 20));
}
