Automapper扩展方法
问题描述
系统中实现了一个自定义的PagedList
/// <summary>
/// Paged list interface
/// </summary>
public interface IPagedList
{
int PageIndex { get; }
int PageSize { get; }
int TotalCount { get; }
int TotalPages { get; }
bool HasPreviousPage { get; }
bool HasNextPage { get; }
}
/// <summary>
/// Paged list interface
/// </summary>
public interface IPagedList<T> : IList<T>, IPagedList
{
}
/// <summary>
/// Paged list
/// </summary>
/// <typeparam name="T">T</typeparam>
[Serializable]
public class PagedList<T> : List<T>, IPagedList<T>
{
/// <summary>
/// Ctor
/// </summary>
/// <param name="source">source</param>
/// <param name="pageIndex">Page index</param>
/// <param name="pageSize">Page size</param>
public PagedList(IQueryable<T> source, int pageIndex, int pageSize)
{
int total = source.Count();
this.TotalCount = total;
this.TotalPages = total / pageSize;
if (total % pageSize > 0)
TotalPages++;
this.PageSize = pageSize;
this.PageIndex = pageIndex;
this.AddRange(source.Skip(pageIndex * pageSize).Take(pageSize).ToList());
}
/// <summary>
/// Ctor
/// </summary>
/// <param name="source">source</param>
/// <param name="pageIndex">Page index</param>
/// <param name="pageSize">Page size</param>
public PagedList(IList<T> source, int pageIndex, int pageSize)
{
TotalCount = source.Count();
TotalPages = TotalCount / pageSize;
if (TotalCount % pageSize > 0)
TotalPages++;
this.PageSize = pageSize;
this.PageIndex = pageIndex;
this.AddRange(source.Skip(pageIndex * pageSize).Take(pageSize).ToList());
}
/// <summary>
/// Ctor
/// </summary>
/// <param name="source">source</param>
/// <param name="pageIndex">Page index</param>
/// <param name="pageSize">Page size</param>
/// <param name="totalCount">Total count</param>
public PagedList(IEnumerable<T> source, int pageIndex, int pageSize, int totalCount)
{
TotalCount = totalCount;
TotalPages = TotalCount / pageSize;
if (TotalCount % pageSize > 0)
TotalPages++;
this.PageSize = pageSize;
this.PageIndex = pageIndex;
this.AddRange(source);
}
public int PageIndex { get; private set; }
public int PageSize { get; private set; }
public int TotalCount { get; private set; }
public int TotalPages { get; private set; }
public bool HasPreviousPage
{
get { return (PageIndex > 0); }
}
public bool HasNextPage
{
get { return (PageIndex + 1 < TotalPages); }
}
}
转换失败，AutoMapper可不认识PagedList
[TestMethod]
public void MapTest2()
{
Mapper.CreateMap<User, UserViewModel>();
var userList = new List<User>()
{
new User() {Name = "Name1", UserId = "UserId1"},
new User() {Name = "Name2", UserId = "UserId2"},
new User() {Name = "Name3", UserId = "UserId3"},
new User() {Name = "Name4", UserId = "UserId4"},
new User() {Name = "Name5", UserId = "UserId5"},
new User() {Name = "Name6", UserId = "UserId6"},
new User() {Name = "Name7", UserId = "UserId7"},
};
var pagedList = new PagedList<User>(userList, 0, 5);
Mapper.Map<PagedList<User>, PagedList<UserViewModel>>(pagedList);//Exception
}
解决方案
/// <summary>
/// The collection extensions.
/// </summary>
public static class ObjectExtensions
{
private static readonly MethodInfo mapMethod;
private static readonly ConcurrentDictionary<Tuple<Type, Type>, Tuple<MethodInfo, Type>> methodsMapper = new ConcurrentDictionary<Tuple<Type, Type>, Tuple<MethodInfo, Type>>();
static ObjectExtensions()
{
mapMethod = (typeof(Mapper)).GetMethods().FirstOrDefault(_ => _.Name == "Map" && _.GetParameters().Length == 1);
}
public static T MapTo<T>(this IPagedList tList) where T : class
{
var totalCount = tList.TotalCount;
var pageIndex = tList.PageIndex;
var pageSize = tList.PageSize;
var t = methodsMapper.GetOrAdd(new Tuple<Type, Type>(tList.GetType(), typeof(T)), _ =>
{
var targetGenericArguments = typeof(T).GenericTypeArguments[0];
var targetGenericArgumentsIEnumerableType = typeof(IEnumerable<>).MakeGenericType(targetGenericArguments);
return new Tuple<MethodInfo, Type>(mapMethod.MakeGenericMethod(targetGenericArgumentsIEnumerableType),
typeof(PagedList<>).MakeGenericType(targetGenericArguments));
});
var rtn2 = t.Item1.Invoke(null, new object[] { tList });
var o2 = Activator.CreateInstance(t.Item2, rtn2, pageIndex, pageSize, totalCount) as T;
return o2;
}
public static T MapTo<T>(this object o) where T : class
{
//way1
//var mapMethod = (typeof(Mapper)).GetMethods().FirstOrDefault(_ => _.Name == "Map" && _.GetParameters().Length == 1 && _.GetGenericArguments().Length == 2 );
//var m2 = mapMethod.MakeGenericMethod(o.GetType(), typeof (T));
//return m2.Invoke(null, new[] { o }) as T;
//way2
return Mapper.Map<T>(o);
}
public static void MapTo<S,T>(this S o,T t) where T : class
{
Mapper.Map(o,t);
}
}
测试通过
[TestMethod]
public void MapTest2()
{
Mapper.CreateMap<User, UserViewModel>();
var userList = new List<User>()
{
new User() {Name = "Name1", UserId = "UserId1"},
new User() {Name = "Name2", UserId = "UserId2"},
new User() {Name = "Name3", UserId = "UserId3"},
new User() {Name = "Name4", UserId = "UserId4"},
new User() {Name = "Name5", UserId = "UserId5"},
new User() {Name = "Name6", UserId = "UserId6"},
new User() {Name = "Name7", UserId = "UserId7"},
};
var pagedList = new PagedList<User>(userList, 0, 5);
var vmPagedList = pagedList.MapTo<PagedList<UserViewModel>>();
Assert.IsTrue(vmPagedList.TotalPages == 2
&& vmPagedList.PageSize == 5
&& vmPagedList.PageIndex == 0
);
}
总结
运行时动态获取泛型参数并执行Mapper.Map<IEnumerable<TSource>, IEnumerable<TDestination>>，并且使用ConcurrentDictionary缓存MethodInfo提高性能。