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IEnumerable support (#20)
* Add support for mapping `IEnumerable` types. * Expand IEnumerable mapping to support additional collection types (`ICollection`, `IReadOnlyList`, `IReadOnlyCollection`) and add tests and documentation accordingly. * Add support for pre-map and post-map queries in enumerable mapping and updated documentation * Improve `Select` query generation to handle context parameter conditionally and add tests for pre-map and post-map query scenarios
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‎docs/AOMDocs.Source/Layout/MainLayout.razor‎

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new (){ Id = "14", Text = "Nested Mapping", Href = "NestedMapping", ParentId = "7", },
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new (){ Id = "15", Text = "Reference Preservation", Href = "ReferencePreservation", ParentId = "7", },
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new (){ Id = "16", Text = "IEnumerable & Collections", Href = "IEnumerableAndCollections", ParentId = "7", },
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new (){ Id = "17", Text = "Pre/Post Map Actions", Href = "PrePostMapActions", ParentId = "7", },
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new (){ Id = "17", Text = "Mapping Polymorphism", Href = "MappingPolymorphism", ParentId = "7", },
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new (){ Id = "18", Text = "Benchmarks", Href = "Benchmarks", },
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new (){ Id = "16", Text = "Enumerable Queries", Href = "EnumerableQueries", ParentId = "7", },
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new (){ Id = "18", Text = "Pre/Post Map Actions", Href = "PrePostMapActions", ParentId = "7", },
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new (){ Id = "19", Text = "Mapping Polymorphism", Href = "MappingPolymorphism", ParentId = "7", },
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new (){ Id = "20", Text = "Benchmarks", Href = "Benchmarks", },
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};
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}
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‎docs/AOMDocs.Source/Pages/EnumerableQueries.razor‎

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@page "/EnumerableQueries"
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<PageTitle>Enumerable Queries</PageTitle>
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<p>
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In addition to automatic enumerable mapping, the mapper allows custom LINQ queries
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to be injected into the collection mapping pipeline.
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</p>
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<p>
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Enumerable queries can be used to filter, reorder, or otherwise transform a collection
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either <em>before</em> or <em>after</em> element mapping occurs.
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</p>
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<p>
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Enumerable queries can use the <code>MapperContext</code> to apply dynamic,
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runtime-controlled behavior during collection mapping.
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</p>
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<p>
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The <code>MapperContext</code> exposes an <code>AdditionalContext</code> dictionary
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that can be populated by the caller and consumed by pre-map and post-map queries.
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</p>
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<h3>Context-driven pre-map queries</h3>
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<p>
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A <code>PreMapQuery</code> can inspect the context to decide which source elements
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should be mapped.
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</p>
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<p>
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This example conditionally excludes inactive users based on a flag stored in the
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mapping context.
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</p>
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<CodeBlock Language="CodeLanguage.CSharp" EnableLineNumbers="false" Code=@PreMapExample />
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<p>
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The context value is provided by the caller at runtime:
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</p>
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<CodeBlock Language="CodeLanguage.CSharp" EnableLineNumbers="false" Code=@ContextSetup />
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<h3>Context-driven post-map queries</h3>
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<p>
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A <code>PostMapQuery</code> can use the context to modify the mapped collection
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without affecting the source mapping.
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</p>
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<p>
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This example conditionally limits the number of mapped results returned.
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</p>
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<CodeBlock Language="CodeLanguage.CSharp" EnableLineNumbers="false" Code=@PostMapExample />
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<h3>Combining pre-map and post-map queries</h3>
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<p>
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Pre-map and post-map queries can be combined to implement complex, policy-driven
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mapping behavior using a single mapper.
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</p>
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<CodeBlock Language="CodeLanguage.CSharp" EnableLineNumbers="false" Code=@BothExample />
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@code
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{
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const string PreMapExample =
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"""
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[GenerateMapper]
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[UseMap<UserMapper, User, UserDto>]
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[Map<Company, CompanyDto>]
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public partial class CompanyMapper_FilterInactiveUsers
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{
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[PreMapQuery<User, UserDto>]
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public static IEnumerable<User> FilterInactiveUsers(IEnumerable<User> users, MapperContext ctx)
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{
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if (!ctx.AdditionalContext.TryGetValue("IncludeInactiveUsers", out var value) ||
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value is not bool includeInactive ||
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includeInactive)
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{
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return users;
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}
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return users.Where(u => u.IsActive);
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}
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}
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""";
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const string PostMapExample =
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"""
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[GenerateMapper]
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[UseMap<UserMapper, User, UserDto>]
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[Map<Company, CompanyDto>]
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public partial class CompanyMapper_LimitResults
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{
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[PostMapQuery<User, UserDto>]
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public static IEnumerable<UserDto> LimitResults(IEnumerable<UserDto> users, MapperContext ctx)
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{
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if (!ctx.AdditionalContext.TryGetValue("MaxUsers", out var value) ||
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value is not int maxUsers)
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{
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return users;
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}
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return users.Take(maxUsers);
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}
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}
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""";
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const string BothExample =
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"""
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[GenerateMapper]
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[UseMap<UserMapper, User, UserDto>]
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[Map<Company, CompanyDto>]
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public partial class CompanyMapper_PolicyDriven
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{
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[PreMapQuery<User, UserDto>]
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public static IEnumerable<User> FilterInactiveUsers(IEnumerable<User> users, MapperContext ctx)
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{
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if (ctx.AdditionalContext.TryGetValue("IncludeInactiveUsers", out var value) &&
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value is bool includeInactive &&
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!includeInactive)
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{
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return users.Where(u => u.IsActive);
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}
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return users;
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}
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[PostMapQuery<User, UserDto>]
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public static IEnumerable<UserDto> LimitResults(IEnumerable<UserDto> users, MapperContext ctx)
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{
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if (ctx.AdditionalContext.TryGetValue("MaxUsers", out var value) &&
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value is int maxUsers)
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{
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return users.Take(maxUsers);
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}
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return users;
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}
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}
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""";
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const string ContextSetup =
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"""
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var ctx = new MapperContext();
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ctx.AdditionalContext["IncludeInactiveUsers"] = false;
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ctx.AdditionalContext["MaxUsers"] = 10;
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var dto = CompanyMapper_PolicyDriven.Map(company, ctx);
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""";
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}

‎docs/AOMDocs.Source/Pages/IEnumerableAndCollections.razor‎

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<PageTitle>IEnumerable & Collections</PageTitle>
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@code {
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<p>
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The mapper supports mapping between enumerable types automatically when a mapping exists for the element type.
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</p>
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<p>
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Any source property that implements <code>IEnumerable&lt;TSource&gt;</code> can be mapped to the following destination types:
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</p>
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<ul>
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<li><code>IEnumerable&lt;TDestination&gt;</code></li>
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<li><code>ICollection&lt;TDestination&gt;</code></li>
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<li><code>List&lt;TDestination&gt;</code></li>
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<li><code>TDestination[]</code></li>
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<li><code>IReadOnlyList&lt;TDestination&gt;</code></li>
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<li><code>IReadOnlyCollection&lt;TDestination&gt;</code></li>
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</ul>
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<p>
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The only requirement is that a mapper exists for <code>TSource</code> to <code>TDestination</code>.
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</p>
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<p>Below is an example mapping a collection of <code>User</code> to <code>UserDto</code>.</p>
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<CodeBlock Language="CodeLanguage.CSharp" EnableLineNumbers="false" Code=@EnumerableMap />
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<p>
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In this example, the <code>Users</code> property on <code>Company</code> implements
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<code>IEnumerable&lt;User&gt;</code>, while the destination property on <code>CompanyDto</code>
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is an array of <code>UserDto</code>.
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</p>
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<p>
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When the project is built, the generated mapper will automatically map each element in the
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source collection using the <code>User → UserDto</code> mapping and materialize the result
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into the target collection type.
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</p>
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<p>
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The generated mapping code will be similar to the following:
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</p>
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<CodeBlock Language="CodeLanguage.CSharp" EnableLineNumbers="false" Code=@GeneratedCode />
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<p>
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Ordering is preserved, and a new destination instance is created for each element in the source collection.
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</p>
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<p>
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This behavior applies equally when mapping to <code>List&lt;T&gt;</code>,
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<code>ICollection&lt;T&gt;</code>, <code>IReadOnlyList&lt;T&gt;</code> and
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<code>IReadOnlyCollection&lt;T&gt;</code>.
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</p>
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@code
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{
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const string EnumerableMap =
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"""
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public class Company
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{
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public ICollection<User> Users { get; set; } =
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[
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User.Jim(),
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User.Jim(),
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];
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}
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public class CompanyDto
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{
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public UserDto[] Users { get; set; } = [];
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}
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[GenerateMapper]
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[Map<User, UserDto>]
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[Map<Company, CompanyDto>]
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public partial class CompanyMapper;
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""";
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const string GeneratedCode =
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"""
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dest.Users = src.Users
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.Select(x => CompanyMapper.Map(x, ctx))
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.ToArray();
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""";
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}

‎src/AotObjectMapper.Abstractions/Attrbutes/PostMapQueryAttribute.cs‎

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namespace AotObjectMapper.Abstractions.Attributes;
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/// <summary>
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/// An attribute that allows the configuration or customization of post-map queries
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/// between the specified source and destination types in an object mapping process.
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/// </summary>
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/// <typeparam name="TSource">The type of the source object being mapped.</typeparam>
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/// <typeparam name="TDestination">The type of the destination object being mapped.</typeparam>
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[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
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public sealed class PostMapQueryAttribute<TSource, TDestination> : Attribute;

‎src/AotObjectMapper.Abstractions/Attrbutes/PreMapQueryAttribute.cs‎

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namespace AotObjectMapper.Abstractions.Attributes;
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/// <summary>
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/// An attribute that allows the configuration or customization of pre-map queries
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/// between the specified source and destination types in an object mapping process.
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/// </summary>
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/// <typeparam name="TSource">The type of the source object being mapped.</typeparam>
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/// <typeparam name="TDestination">The type of the destination object being mapped.</typeparam>
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[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
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public class PreMapQueryAttribute<TSource, TDestination> : Attribute { }

‎src/AotObjectMapper.Mapper/Mapper/MapperGenerator.cs‎

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sb.AppendLine("// <auto-generated />");
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sb.AppendLine("");
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sb.AppendLine("using System;");
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sb.AppendLine("using System.Collections.Generic;");
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sb.AppendLine("using System.Linq;");
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sb.AppendLine("using System.ComponentModel;");
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sb.AppendLine("using AotObjectMapper.Abstractions.Models;");
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sb.AppendLine("");

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