// -----------------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
// -----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using Microsoft.Internal;
namespace System.ComponentModel.Composition.Primitives{
/// <summary>
/// Describes the contract that an <see cref="Export"/> object satisfies.
/// </summary>
public class ExportDefinition
{
// Unlike contract name, metadata has a sensible default; set it to an empty bag,
// so that derived definitions only need to override ContractName by default.
private readonly IDictionary<string, object> _metadata = MetadataServices.EmptyMetadata;
private readonly string _contractName;
/// <summary>
/// Initializes a new instance of the <see cref="ExportDefinition"/> class.
/// </summary>
/// <remarks>
/// <note type="inheritinfo">
/// Derived types calling this constructor must override <see cref="ContractName"/>
/// and optionally, <see cref="Metadata"/>. By default, <see cref="Metadata"/>
/// returns an empty, read-only dictionary.
/// </note>
/// </remarks>
protected ExportDefinition()
{
}
/// <summary>
/// Initializes a new instance of the <see cref="ExportDefinition"/> class with
/// the specified contract name and metadata.
/// </summary>
/// <param name="contractName">
/// A <see cref="String"/> containing the contract name of the
/// <see cref="ExportDefinition"/>.
/// </param>
/// <param name="metadata">
/// An <see cref="IDictionary{TKey, TValue}"/> containing the metadata of the
/// <see cref="ExportDefinition"/>; or <see langword="null"/> to set the
/// <see cref="Metadata"/> property to an empty, read-only
/// <see cref="IDictionary{TKey, TValue}"/>.
/// </param>
/// <exception cref="ArgumentNullException">
/// <paramref name="contractName"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="ArgumentException">
/// <paramref name="contractName"/> is an empty string ("").
/// </exception>
public ExportDefinition(string contractName, IDictionary<string, object> metadata)
{
Requires.NotNullOrEmpty(contractName, "contractName");
_contractName = contractName;
if (metadata != null)
{
_metadata = metadata.AsReadOnly();
}
}
/// <summary>
/// Gets the contract name of the export definition.
/// </summary>
/// <value>
/// A <see cref="String"/> containing the contract name of the
/// <see cref="ExportDefinition"/>.
/// </value>
/// <exception cref="NotImplementedException">
/// The property was not overridden by a derived class.
/// </exception>
/// <remarks>
/// <note type="inheritinfo">
/// Overriders of this property should never return <see langword="null"/>
/// or an empty string ("").
/// </note>
/// </remarks>
public virtual string ContractName
{
get
{
if (_contractName != null)
{
return _contractName;
}
throw ExceptionBuilder.CreateNotOverriddenByDerived("ContractName");
}
}
/// <summary>
/// Gets the metadata of the export definition.
/// </summary>
/// <value>
/// An <see cref="IDictionary{TKey, TValue}"/> containing the metadata of the
/// <see cref="ExportDefinition"/>. The default is an empty, read-only
/// <see cref="IDictionary{TKey, TValue}"/>.
/// </value>
/// <remarks>
/// <para>
/// <note type="inheritinfo">
/// Overriders of this property should return a read-only
/// <see cref="IDictionary{TKey, TValue}"/> object with a case-sensitive,
/// non-linguistic comparer, such as <see cref="StringComparer.Ordinal"/>,
/// and should never return <see langword="null"/>.
/// If the <see cref="ExportDefinition"/> does not contain metadata
/// return an empty <see cref="IDictionary{TKey, TValue}"/> instead.
/// </note>
/// </para>
/// </remarks>
public virtual IDictionary<string, object> Metadata
{
get { return _metadata; }
}
/// <summary>
/// Returns a string representation of the export definition.
/// </summary>
/// <returns>
/// A <see cref="String"/> containing the value of the <see cref="ContractName"/> property.
/// </returns>
public override string ToString()
{
return this.ContractName;
}
}
}
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