/// <summary>
/// This is helper method, which checks whether one or both of the given objects are <c>null</c>, and if so, assigns comparison result appropriate to this <see cref="NullSorting"/> enumeration, and returns <c>false</c>.
/// If neither of the given objects are <c>null</c>, this then returns <c>true</c>.
/// </summary>
/// <param name="nullSortingStrategy">This <see cref="NullSorting"/> strategy.</param>
/// <param name="x">The first argument to comparison.</param>
/// <param name="y">The second argument to comparison.</param>
/// <param name="comparisonResult">This parameter will hold the result of the comparison, if <paramref name="x"/> or <paramref name="y"/> or both are <c>null</c>.</param>
/// <returns><c>true</c> if <paramref name="x"/> and <paramref name="y"/> are both non-<c>null</c>; <c>false</c> otherwise.</returns>
public static Boolean CheckForNullValues(this NullSorting nullSortingStrategy, Object x, Object y, out Int32 comparisonResult)
{
Boolean retVal;
if (x == null)
{
retVal = false;
comparisonResult = y == null ? 0 : (nullSortingStrategy == NullSorting.NullsFirst ? -1 : 1);
}
else if (y == null)
{
retVal = false;
comparisonResult = nullSortingStrategy == NullSorting.NullsFirst ? 1 : -1;
}
else
{
retVal = true;
comparisonResult = 0;
}
return(retVal);
}
internal ComparerWithFunctionAndNullStrategy(Comparison <T> compareFunc, NullSorting nullSorting)
{
ArgumentValidator.ValidateNotNull("Comparer function", compareFunc);
this._compareFunc = compareFunc;
this._nullSorting = nullSorting;
}
/// <summary>
/// Creates a new <see cref="IComparer{T}"/> which behaves as <paramref name="comparison"/> callback specify, and which sorts <c>null</c> values according to given strategy.
/// This means that the given callback will never receive <c>null</c> values.
/// </summary>
/// <typeparam name="T">The type of object being compared.</typeparam>
/// <param name="comparison">The function comparing the object, should return same as <see cref="IComparer{T}.Compare(T,T)"/> method.</param>
/// <param name="nullSortingStrategy">The strategy to sort <c>null</c> values.</param>
/// <returns>A new <see cref="IComparer{T}"/> which behaves as parameters specify.</returns>
/// <exception cref="ArgumentNullException">If <paramref name="comparison"/> is <c>null</c>.</exception>
/// <remarks>The return value can be casted to <see cref="System.Collections.IComparer"/>.</remarks>
public static IComparer <T> NewComparerWithNullStrategy <T>(Comparison <T> comparison, NullSorting nullSortingStrategy)
{
return(new ComparerWithFunctionAndNullStrategy <T>(comparison, nullSortingStrategy));
}
