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Autofac / src / Source / Autofac / Core / Parameter.cs

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// This software is part of the Autofac IoC container
// Copyright © 2011 Autofac Contributors
// http://autofac.org
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.

using System;
using System.Reflection;

namespace Autofac.Core
{
    /// <summary>
    /// Used in order to provide a value to a constructor parameter or property on an instance
    /// being created by the container.
    /// </summary>
    /// <remarks>
    /// Not all parameters can be applied to all sites.
    /// </remarks>
    public abstract class Parameter
    {
        /// <summary>
        /// Returns true if the parameter is able to provide a value to a particular site.
        /// </summary>
        /// <param name="pi">Constructor, method, or property-mutator parameter.</param>
        /// <param name="context">The component context in which the value is being provided.</param>
        /// <param name="valueProvider">If the result is true, the valueProvider parameter will
        /// be set to a function that will lazily retrieve the parameter value. If the result is false,
        /// will be set to null.</param>
        /// <returns>True if a value can be supplied; otherwise, false.</returns>
        public abstract bool CanSupplyValue(ParameterInfo pi, IComponentContext context, out Func<object> valueProvider);
    }
}