#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 System.Runtime.Serialization;
namespace Spring.Expressions{
/// <summary>
/// Represents parsed selection node in the navigation expression.
/// </summary>
/// <author>Aleksandar Seovic</author>
[Serializable]
public class SelectionFirstNode : BaseNode
{
/// <summary>
/// Create a new instance
/// </summary>
public SelectionFirstNode():base()
{
}
/// <summary>
/// Create a new instance from SerializationInfo
/// </summary>
protected SelectionFirstNode(SerializationInfo info, StreamingContext context)
: base(info, context)
{
}
/// <summary>
/// Returns the first context item that matches selection expression.
/// </summary>
/// <param name="context">Context to evaluate expressions against.</param>
/// <param name="evalContext">Current expression evaluation context.</param>
/// <returns>Node's value.</returns>
protected override object Get(object context, EvaluationContext evalContext)
{
IEnumerable enumerable = context as IEnumerable;
if (enumerable == null)
{
throw new ArgumentException(
"Selection can only be used on an instance of the type that implements IEnumerable.");
}
BaseNode expression = (BaseNode) this.getFirstChild();
using (evalContext.SwitchThisContext())
{
foreach (object o in enumerable)
{
evalContext.ThisContext = o;
bool isMatch = (bool)GetValue(expression, o, evalContext);
if (isMatch)
{
return o;
}
}
}
return null;
}
}
}
|