AutoMapper投影誤差

我在網上API獲得方法：AutoMapper投影誤差

public async Task<IHttpActionResult> Get() 
{ 
    var categories = await _context.Categories.Include(x => x.SubCategories) 
            .Where(c => c.IsActive) 
            .ToListAsync(); 
    var outPut = AutoMapper.Mapper.Map<List<CategoryDto>>(categories); 
    return Ok(outPut); 
}

此方法按預期工作。但我不想從數據庫中檢索所有記錄，然後映射到DTO並返回結果。我想要使用AutoMapper.QueryableExtensions並只選擇必填字段。

var categories = await _context.Categories.Include(x => x.SubCategories) 
              .Where(c => c.IsActive) 
              .ProjectTo<List<CategoryDto>>() 
              .ToListAsync();

在映射配置我這樣定義的映射：

public static void Config() 
{ 
    AutoMapper.Mapper.Initialize(config => 
    { 
     config.CreateMap<SubCategory, SubCategoryDto>(); 
     config.CreateMap<Category, CategoryDto>().ForMember(
        des=>des.SubCategoriesCount, 
        opt=>opt.MapFrom(src=>src.SubCategories.Count)); 
    }); 

}

在運行我得到以下異常

「exceptionMessage」：「從CategoriesAndBrandsServices.Models.Category缺少地圖系統.Collections.Generic.List 1[CategoriesAndBrandsServices.Dtos.CategoryDto]. Create using Mapper.CreateMap<Category, List 1>。「，」exceptionType「：」System.InvalidOperationException「，」stackTrace「：」at AutoMa在AutoMapper.QueryableExtensions.ExpressionBuilder.CreateMapExpression（ExpressionRequest請求）\ r \ n在AutoMapper.LockingConcurrentDictionary 2.<>c__DisplayClass2_1.<.ctor>b__1()\r\n at System.Lazy 1.CreateValue（）\ pper.QueryableExtensions.ExpressionBuilder.CreateMapExpression（ExpressionRequest請求，表達式instanceParameter，IDictionary 2 typePairCount)\r\n at AutoMapper.QueryableExtensions.ExpressionBuilder.CreateMapExpression(ExpressionRequest request, IDictionary 2 typePairCount）\ r \ r \ n at System.Lazy 1.LazyInitValue()\r\n at System.Lazy 1.get_Value（）\ r \ n at AutoMapper.LockingConcurrentDictionary 2.GetOrAdd(TKey key)\r\n at AutoMapper.QueryableExtensions.ExpressionBuilder.CreateMapExpression(Type sourceType, Type destinationType, IDictionary 2 parameters，MemberInfo [] membersToExpand）\ r \ n at AutoMapper.QueryableExtensions.ProjectionExpression.To [TResult]（IDictionary 2 parameters, IEnumerable 1 memberPathsToExpand ）\ r \ n在AutoMapper.QueryableExtensions.Extensions.ProjectTo [TDestination]（IQueryable來源，表達式1[] membersToExpand)\r\n at CategoriesAndBrandsServices.Controllers.CategoriesController.<Get>d__0.MoveNext() in c:\\OnlineShoppingWebsite\\Services\\CategoriesAndBrandsServices\\CategoriesAndBrandsServices\\Controllers\\CategoriesController.cs:line 24\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter 1）[AutoSetper.QueryableExtensions.ProjectionExpression.To [TResult]（Object parameters，Expression 1[] membersToExpand)\r\n at AutoMapper.QueryableExtensions.Extensions.ProjectTo[TDestination](IQueryable source, IConfigurationProvider configuration, Object parameters, Expression 1 [] membersToExpand）\ r \ n） Sy上的GetResult（）\ r \ n stem.Threading.Tasks.TaskHelpersExtensions.d__3 1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter 1.GetResult（）\ r \ n在System.Web.Http.Controllers.ApiControllerActionInvoker.d__0.MoveNext（）\ r \ n ---從上一個位置結束堆棧跟蹤在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任務任務）上運行System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（任務任務）\ r \ n時拋出異常--- \ r \ n \ .CompilerServices.TaskAwaiter 1.GetResult()\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter 1.GetResult（個）\ r \ n在System.Web.Http.Dispatcher.HttpControllerDispatcher.d__1.MoveNext（）」

來源

2017-01-09 MANISH KUMAR CHOUDHARY

我認爲項目是一對一的，你試試從類別到類別dtos列表投擲因此，嘗試用此來回報項目。

.ProjectTo<CategoryDto>()

PS。從異常「Missing從CategoriesAndBrandsServices.Models.Category映射到System.Collections.Generic.List1 [CategoriesAndBrandsServices.Dtos.CategoryDto]。使用Mapper.CreateMap創建。」

來源

2017-01-09 05:43:36

這不起作用。我已經嘗試過了。而且項目有一對多的關係。如果你將檢查映射配置的類別，你可以很容易地找出它有一對多的關係。 –

請嘗試再做一次，併發布異常。 –

我沒有看到一對多的問題，現在異常告訴你，你嘗試將類別轉換爲列表，所以請儘量做我寫的併發布我的其他異常。 –

AutoMapper投影誤差

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