#region License
/*
* Copyright 2002-2005 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#endregion
using System;
using System.Collections;
using Spring.Collections;
namespace Spring.Expressions.Processors{
/// <summary>
/// Implementation of the distinct processor.
/// </summary>
/// <author>Aleksandar Seovic</author>
public class DistinctProcessor : ICollectionProcessor
{
/// <summary>
/// Returns distinct items from the collection.
/// </summary>
/// <param name="source">
/// The source collection to process.
/// </param>
/// <param name="args">
/// 0: boolean flag specifying whether to include <c>null</c>
/// in the results or not. Default is false, which means that
/// <c>null</c> values will not be included in the results.
/// </param>
/// <returns>
/// A collection containing distinct source collection elements.
/// </returns>
/// <exception cref="ArgumentException">
/// If there is more than one argument, or if the single optional argument
/// is not <b>Boolean</b>.
/// </exception>
public object Process(ICollection source, object[] args)
{
if (source == null)
{
return null;
}
bool includeNulls = false;
if (args.Length == 1)
{
if (args[0] is bool)
{
includeNulls = (bool) args[0];
}
else
{
throw new ArgumentException("distinct() processor argument must be a boolean value.");
}
}
else if (args.Length > 1)
{
throw new ArgumentException("Only a single argument can be specified for a distinct() processor.");
}
HybridSet set = new HybridSet(source);
if (!includeNulls)
{
set.Remove(null);
}
return set;
}
}
}
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