在我的映射逻辑层(从Model到ViewModel),我正在尝试填充一个SelectListItem,以便在我的编辑视图中与HTML.DropDownListFor助手一起使用。
我尝试在以下代码示例中使用查询来检索品牌名称列表,以填充SelectListItem,但触发了以下异常:
“已经有与此命令关联的打开的DataReader,必须首先关闭它。”
映射
我知道有一个简单的解决方法,即在连接字符串中启用多活动结果集(MARS),但我想知道是否有一种方法可以在不修改连接字符串的情况下实现我的目标。
以下是更多可能有助于解决此问题的类:
[EntityCommandExecutionException: 在执行命令定义时发生错误。有关详细信息,请参阅内部异常。] System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +507 System.Data.Objects.Internal.ObjectQueryExecutionPlan.Execute(ObjectContext context, ObjectParameterCollection parameterValues) +730 System.Data.Objects.ObjectQuery
我尝试在以下代码示例中使用查询来检索品牌名称列表,以填充SelectListItem,但触发了以下异常:
“已经有与此命令关联的打开的DataReader,必须首先关闭它。”
映射
public class MedicalProductMapper
{
private MvcMedicalStoreDb _db; // DataContext class
public MedicalProductMapper(MvcMedicalStoreDb db)
{
_db = db;
}
public MedicalProductViewModel GetMedicalProductViewModel(MedicalProduct source)
{
MedicalProductViewModel viewModel = new MedicalProductViewModel();
viewModel.ID = source.ID;
viewModel.Name = source.Name;
viewModel.Price = source.Price;
viewModel.BrandID = source.BrandID;
// This following line produces the exception
viewModel.BrandName = _db.Brands.Single(b => b.ID == source.BrandID).Name;
var queryBrands = from b in _db.Brands
select b;
viewModel.BrandSelectListItem = queryBrands as IEnumerable<SelectListItem>;
return viewModel;
}
}
我知道有一个简单的解决方法,即在连接字符串中启用多活动结果集(MARS),但我想知道是否有一种方法可以在不修改连接字符串的情况下实现我的目标。
以下是更多可能有助于解决此问题的类:
编辑视图
@model MvcMedicalStore.Models.MedicalProductViewModel
@{
ViewBag.Title = "Edit";
}
<h2>Edit</h2>
@using (Html.BeginForm()) {
@Html.AntiForgeryToken()
@Html.ValidationSummary(true)
<fieldset>
<legend>MedicalProduct</legend>
@Html.HiddenFor(model => model.ID)
<div class="editor-label">
@Html.LabelFor(model => model.Name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Name)
@Html.ValidationMessageFor(model => model.Name)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.Price)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Price)
@Html.ValidationMessageFor(model => model.Price)
</div>
// BRAND NAME
<div class="editor-label">
@Html.LabelFor(model => model.BrandName)
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.BrandName, Model.BrandSelectListItem)
@Html.ValidationMessageFor(model => model.BrandName)
</div>
<p>
<input type="submit" value="Save" />
</p>
</fieldset>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}
控制器:
public class MedicalProductController : Controller
{
private MvcMedicalStoreDb _db = new MvcMedicalStoreDb();
//
// GET: /MedicalSupply/
public ActionResult Index()
{
var viewModel = _db.Products.AsEnumerable()
.Select(product => GetMedicalProductViewModel(product));
return View(viewModel);
}
public MedicalProductViewModel GetMedicalProductViewModel(MedicalProduct product)
{
var mapper = new MedicalProductMapper(_db);
return mapper.GetMedicalProductViewModel(product);
}
public MedicalProduct GetMedicalProduct(MedicalProductViewModel viewModel)
{
var mapper = new MedicalProductMapper(_db);
return mapper.GetMedicalProduct(viewModel);
}
//
// GET: /MedicalSupply/Edit/5
public ActionResult Edit(int id = 0)
{
MedicalProduct medicalProduct = _db.Products.Find(id);
if (medicalProduct == null)
{
return HttpNotFound();
}
var viewModel = GetMedicalProductViewModel(medicalProduct);
return View(viewModel);
}
//
// POST: /MedicalSupply/Edit/5
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(MedicalProduct medicalProduct)
{
if (ModelState.IsValid)
{
_db.Entry(medicalProduct).State = EntityState.Modified;
_db.SaveChanges();
return RedirectToAction("Index");
}
var viewModel = GetMedicalProductViewModel(medicalProduct);
return View(viewModel);
}
}
Stack Trace
[InvalidOperationException: 已经有一个与此命令关联的打开的DataReader,必须先关闭它。] System.Data.SqlClient.SqlInternalConnectionTds.ValidateConnectionForExecute(SqlCommand command) +5287423 System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute(String method, SqlCommand command) +20 System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async) +155 System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite) +82 System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) +53 System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) +134 System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior) +41 System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior) +10 System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +437[EntityCommandExecutionException: 在执行命令定义时发生错误。有关详细信息,请参阅内部异常。] System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +507 System.Data.Objects.Internal.ObjectQueryExecutionPlan.Execute(ObjectContext context, ObjectParameterCollection parameterValues) +730 System.Data.Objects.ObjectQuery
1.GetResults(Nullable
1 forMergeOption) +131
System.Data.Objects.ObjectQuery1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() +36 System.Linq.Enumerable.Single(IEnumerable
1 source) +179 System.Data.Objects.ELinq.ObjectQueryProvider.b_3(IEnumerable1 sequence) +41
System.Data.Objects.ELinq.ObjectQueryProvider.ExecuteSingle(IEnumerable
1 query, Expression queryRoot) +59
System.Data.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression) +133
System.Data.Entity.Internal.Linq.DbQueryProvider.Execute(Expression expression) +123 System.Linq.Queryable.Single(IQueryable1 source, Expression
1 predicate) +287
MvcMedicalStore.Mappers.MedicalProductMapper.GetMedicalProductViewModel(MedicalProduct source) in c:\Users\Matt\Documents\Visual Studio 2012\Projects\MvcMedicalStore\MvcMedicalStore\Mappers\MedicalProductMapper.cs:28
MvcMedicalStore.Controllers.<>c_DisplayClass1.b_0(MedicalProduct product) in c:\Users\Matt\Documents\Visual Studio 2012\Projects\MvcMedicalStore\MvcMedicalStore\Controllers\HomeController.cs:28
System.Linq.WhereSelectEnumerableIterator2.MoveNext() +145
ASP._Page_Views_Home_Index_cshtml.Execute() in c:\Users\Matt\Documents\Visual Studio 2012\Projects\MvcMedicalStore\MvcMedicalStore\Views\Home\Index.cshtml:25
System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197
System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +119
System.Web.WebPages.StartPage.RunPage() +17
System.Web.WebPages.StartPage.ExecutePageHierarchy() +62
System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +76
System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +743
System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +382
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +431 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +39
System.Web.Mvc.<>c_DisplayClass1a.<InvokeActionResultWithFilters>b__17() +74 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func
1 continuation) +388
System.Web.Mvc.<>c_DisplayClass1c.b_19() +72 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 filters, ActionResult actionResult) +303
System.Web.Mvc.Async.<>c__DisplayClass2a.<BeginInvokeAction>b__20() +155 System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +184 System.Web.Mvc.Async.WrappedAsyncResult
1.End() +136 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56