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ExpressionParameterReplacer.cs
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ExpressionParameterReplacer.cs
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/* Copyright 2010-present MongoDB Inc.
*
* 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.
*/
using System.Linq.Expressions;
namespace MongoDB.Driver.Linq
{
/// <summary>
/// A class that replaces all occurences of one parameter with a different parameter.
/// </summary>
public class ExpressionParameterReplacer : ExpressionVisitor
{
// private fields
private ParameterExpression _fromParameter;
private Expression _toExpression;
// constructors
/// <summary>
/// Initializes a new instance of the ExpressionParameterReplacer class.
/// </summary>
/// <param name="fromParameter">The parameter to be replaced.</param>
/// <param name="toExpression">The expression that replaces the parameter.</param>
public ExpressionParameterReplacer(ParameterExpression fromParameter, Expression toExpression)
{
_fromParameter = fromParameter;
_toExpression = toExpression;
}
// public methods
/// <summary>
/// Replaces all occurences of one parameter with a different parameter.
/// </summary>
/// <param name="node">The expression containing the parameter that should be replaced.</param>
/// <param name="fromParameter">The from parameter.</param>
/// <param name="toExpression">The expression that replaces the parameter.</param>
/// <returns>The expression with all occurrences of the parameter replaced.</returns>
public static Expression ReplaceParameter(Expression node, ParameterExpression fromParameter, Expression toExpression)
{
var replacer = new ExpressionParameterReplacer(fromParameter, toExpression);
return replacer.Visit(node);
}
/// <summary>
/// Replaces the from parameter with the two parameter if it maches.
/// </summary>
/// <param name="node">The node.</param>
/// <returns>The parameter (replaced if it matched).</returns>
protected override Expression VisitParameter(ParameterExpression node)
{
if (node == _fromParameter)
{
return _toExpression;
}
return node;
}
}
}