系统修改了哪些步骤？枚举操作可能无法执行。错误？ [英] What steps to get rid of Collection was modified; enumeration operation may not execute. Error?
本文介绍了系统修改了哪些步骤？枚举操作可能无法执行。错误？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
//让我们创建一些内存数据
//创建一个Customer
列表< Customer> listOfCustomers = new List< BlahBlahExample.Domain.Objects.Customer>（）
{new Customer {CustomerID =1，Orders = new HashSet< Order>（），CustomerDemographics = new HashSet< CustomerDemographic>（），CompanyName =芝加哥公牛队，ContactName =Michael Jordan，ContactTitle =top basket ball player，Address =332 testing lane，City =Chicago，Region =Illinois，PostalCode =484894，Country = USA，Phone =3293993，Fax =39393}，
new Customer {CustomerID =2，Orders = new HashSet< Order>（），CustomerDemographics = new HashSet< CustomerDemographic>（） CompanyName =迈阿密热火，ContactName =Lebron James，ContactTitle =第二好篮球选手，地址=90 test street，City =Miami，Region =Florida，PostalCode =4869394 Country =USA，Phone =3293213，Fax =33393}，
new Customer {CustomerI D =3，Orders = new HashSet< Order>（），CustomerDemographics = new HashSet< CustomerDemographic>（），CompanyName =Oklahoma City Thunder，ContactName =Kevin Durant，ContactTitle =当前顶级篮球球员 ，Address =35 test row，City =Oklahoma City，Region =Oklahoma，PostalCode =480290，Country =USA，Phone =304923，Fax =33325}
};
//将列表转换为IQueryable列表
IQueryable< Customer> queryableListOfCustomerInMemoryData = listOfCustomers.AsQueryable（）;
//让我们创建一个Mocked DbSet对象。
Mock< DbSet< BlahBlahExample.Domain.Objects.Customer>> mockDbSet = new Mock< DbSet< BlahBlahExample.Domain.Objects.Customer>>（）;
//强制DbSet返回我们转换的列表对象的IQueryable成员
//作为
//数据源
mockDbSet.As< IQueryable&BlanBlahExample。 Domain.Objects.Customer>>（）。Setup（m => m.Provider）.Returns（queryableListOfCustomerInMemoryData.Provider）;
mockDbSet.As< IQueryable< BlahBlahExample.Domain.Objects.Customer>>（）。Setup（m => m.Expression）.Returns（queryableListOfCustomerInMemoryData.Expression）;
mockDbSet.As< IQueryable< BlahBlahExample.Domain.Objects.Customer>>（）。Setup（m => m.ElementType）.Returns（queryableListOfCustomerInMemoryData.ElementType）;
mockDbSet.As< IQueryable< BlahBlahExample.Domain.Objects.Customer>>（）。Setup（m => m.GetEnumerator（））返回（queryableListOfCustomerInMemoryData.GetEnumerator（））;
mockDbSet.Setup（m => m.Add（It.IsAny< Customer>（）））。回调< Customer>（listOfCustomers.Add）;
Mock< BlahBlahAuditMappingProvider> jsAudtMppngPrvdr = new Mock< BlahBlahAuditMappingProvider>（）;
Mock< BlahBlahDataContext> fctry = new Mock< BlahBlahDataContext>（jsAudtMppngPrvdr.Object）;
Mock< BlahBlahDataContext> qryCtxt = new Mock< BlahBlahDataContext>（）;
Mock< BlahBlahAuditContext> audtCtxt = new Mock< BlahBlahAuditContext>（）;
Mock< BlahBlahDataContext> mockedReptryCtxt = new Mock< BlahBlahDataContext>（）;
mockedReptryCtxt.Setup（q => q.Customers）.Returns（mockDbSet.Object）;
mockedReptryCtxt.Setup（q => q.Set< Customer>（））。Returns（mockDbSet.Object）;
mockedReptryCtxt.CallBase = true;
DbSet< Customer> inMemoryDbSetCustomer = mockedReptryCtxt.Object.Set< Customer>（）;
在下面的代码摘录（这是我们的Test In Test）中，我添加了一个新的客户到现有的内存数据，然后在Mocked对象上调用SaveChanges。
Customer returnCust =（Customer）（mockedReptryCtxt （）CustomerList = new HashSet< Order>（），CustomerDemographics = new HashSet< CustomerDemographic>（），CompanyName =Kolkota Knights，ContactName = Sachin Tendulkar，ContactTitle =当前顶级板球运动员，Address =35 test row，City =Kolkota，Region =West Bengal，PostalCode =3454534，Country =India，Phone = 304923，Fax =33325}））;
mockedReptryCtxt.Object.SaveChanges（）;
稍后在代码中，我有以下摘录的代码，其中_context.Set（）将返回我们之前创建的In-Memory Data DBSet
var query = _context.Set< TEntity>（）。AsQueryable（）;
if（typeof（TEntity）.Name.Contains（Audit））
{
return query;
}
if（includes！= null&& includes.Any（））
{
foreach（var include in includes）
{
query = query.Include（include）;
}
}
列表< TEntity> resultsAsList = query.ToList（）; //错误Thrown当使用ToList（）
var results = resultsAsList.AsQueryable（）;
当我们调用ToList（）时，它会抛出以下错误：
System.InvalidOperationException被用户代码未处理
HResult = -2146233079
Message =集合被修改;枚举操作可能无法执行。
Source = mscorlib
StackTrace：
在System.ThrowHelper.ThrowInvalidOperationException（ExceptionResource资源）
在System.Collections.Generic.List`1.Enumerator.MoveNextRare（）
在System.Collections.Generic.List`1.Enumerator.MoveNext（）
在System.Collections.Generic.List`1..ctor（IEnumerable`1集合）
在System.Linq.Enumerable .dList [TSource]（IEnumerable`1 source）
在BlahBlah.Framework.EntityFramework.EntityFrameworkRepository`1.ConcreteQuery（List`1 includes）在d：\EMIS\BlahBlah Framework\BlahBlahFrameworkLightweight\BlahBlah中。 Framework.EntityFramework\EntityFrameworkRepository.cs：line 51
在Castle.Proxies.EntityFrameworkRepository`1Proxy.ConcreteQuery_callback（List`1 includes）
在Castle.Proxies.Invocations.EntityFrameworkRepository`1_ConcreteQuery.InvokeMethodOnTarget（）
在Castle.DynamicProxy.AbstractInvocation.Proceed（）
在Moq.Proxy.CastleProxyFactory.CallContext.InvokeBase（）
在Moq.InvokeBase.HandleIntercept（ICallContext调用，InterceptorContext ctx，CurrentInterceptContext localctx）
在Moq.Interceptor.Intercept（ICallContext调用）
在Moq.Proxy.CastleProxyFactory.Interceptor.Intercept（IInvocation调用）
在Castle.DynamicProxy.AbstractInvocation.Proceed（）
在Castle.Proxies.EntityFrameworkRepository`1Proxy.ConcreteQuery（List`1包括）
在BlahBlah.Framework.Core.Repository.BaseRepository`1.Query（List`1 includes）在d：\EMIS\BlahBlah Framework\BlahBlahFrameworkLightweight\BlahBlah.Framework.Core\Repository\BaseRepository.cs ：Castle.Proxies.EntityFrameworkRepository`1Proxy.Query_callback（List`1 includes）$ 149
在Castle.Proxies.Invocations.IRepository`1_Query.InvokeMethodOnTarget（）
在Castle.DynamicProxy。抽象Moq.Proxy.CastleProxyFactory.CallContext.InvokeBase（）中的
Moq.InvokeBase.HandleIntercept（ICallContext调用，InterceptorContext ctx，CurrentInterceptContext localctx）
在Moq.Interceptor处的
。 Intercept（ICallContext invocation）
在Moq.Proxy.CastleProxyFactory.Interceptor.Intercept（IInvocation调用）
在Castle.DynamicProxy.AbstractInvocation.Proceed（）
在Castle.Proxies.EntityFrameworkRepository`1Proxy。查询（List`1包括）
在BlahBlah.Test.Unit.CntrlrsTests.CustomerControllerTest.Test_Creation_Of_Customer_Using_Constructor_Of _Customer_Controller_That_Expects_Arguments（）在d：\EMIS\BlahBlah Framework\BlahBlahFrameworkLightweight\BlahBlah.Test.Unit\CntrlrsTests\\ \\ CustomerControllerTest.cs：行278
InnerException：
我们需要采取哪些步骤命令停止说e我们发现一个非常笨拙的解决方案：
解决方案
/ p>
列表< TEntity> tempList = new List< TEntity>（）; （int i = query.Count（） - 1; i> = 0; i--）
{
tempList.Add（query.ElementAt（i））
）;
}
列表< TEntity> resultsAsList = tempList.ToList（）;
var results = resultsAsList.AsQueryable（）;
在上述代码中，使用索引的for循环遍历DBSet很重要实例。此外，在循环中，您将每个元素添加到列表。 （基本上，避免使用迭代器很重要）
Our programming involves some Mock testing using In-Memory Data. Therefore, we implemented the following code that would first create In-Memory Data of Customer objects
// Let us create some in-memory data
// Create a list of Customer
List<Customer> listOfCustomers = new List<BlahBlahExample.Domain.Objects.Customer>()
{ new Customer { CustomerID = "1 ",Orders = new HashSet<Order>(), CustomerDemographics = new HashSet<CustomerDemographic>(), CompanyName = "Chicago Bulls", ContactName = "Michael Jordan", ContactTitle = "top basket ball player", Address = "332 testing lane", City = "Chicago", Region = "Illinois", PostalCode = "484894", Country = "USA", Phone = "3293993", Fax = "39393" },
new Customer { CustomerID = "2 ",Orders = new HashSet<Order>(),CustomerDemographics = new HashSet<CustomerDemographic>() , CompanyName = "Miami Heat", ContactName = "Lebron James", ContactTitle = "second best basket ball player", Address = "90 test street", City = "Miami", Region = "Florida", PostalCode = "4869394", Country = "USA", Phone = "3293213", Fax = "33393" },
new Customer { CustomerID = "3 ",Orders = new HashSet<Order>(),CustomerDemographics = new HashSet<CustomerDemographic>() , CompanyName = "Oklahoma City Thunder", ContactName = "Kevin Durant", ContactTitle = "current top basket ball player", Address = "35 test row", City = "Oklahoma City", Region = "Oklahoma", PostalCode = "480290", Country = "USA", Phone = "304923", Fax = "33325" }
};
// Convert the list to an IQueryable list
IQueryable<Customer> queryableListOfCustomerInMemoryData = listOfCustomers.AsQueryable();
// Let us create a Mocked DbSet object.
Mock<DbSet<BlahBlahExample.Domain.Objects.Customer>> mockDbSet = new Mock<DbSet<BlahBlahExample.Domain.Objects.Customer>>();
// Force DbSet to return the IQueryable members
// of our converted list object as its
// data source
mockDbSet.As<IQueryable<BlahBlahExample.Domain.Objects.Customer>>().Setup(m => m.Provider).Returns(queryableListOfCustomerInMemoryData.Provider);
mockDbSet.As<IQueryable<BlahBlahExample.Domain.Objects.Customer>>().Setup(m => m.Expression).Returns(queryableListOfCustomerInMemoryData.Expression);
mockDbSet.As<IQueryable<BlahBlahExample.Domain.Objects.Customer>>().Setup(m => m.ElementType).Returns(queryableListOfCustomerInMemoryData.ElementType);
mockDbSet.As<IQueryable<BlahBlahExample.Domain.Objects.Customer>>().Setup(m => m.GetEnumerator()).Returns(queryableListOfCustomerInMemoryData.GetEnumerator());
mockDbSet.Setup(m => m.Add(It.IsAny<Customer>())).Callback<Customer>(listOfCustomers.Add);
Mock<BlahBlahAuditMappingProvider> jsAudtMppngPrvdr = new Mock<BlahBlahAuditMappingProvider>();
Mock<BlahBlahDataContext> fctry = new Mock<BlahBlahDataContext>(jsAudtMppngPrvdr.Object);
Mock<BlahBlahDataContext> qryCtxt = new Mock<BlahBlahDataContext>();
Mock<BlahBlahAuditContext> audtCtxt = new Mock<BlahBlahAuditContext>();
Mock<BlahBlahDataContext> mockedReptryCtxt = new Mock<BlahBlahDataContext>();
mockedReptryCtxt.Setup(q => q.Customers).Returns(mockDbSet.Object);
mockedReptryCtxt.Setup(q => q.Set<Customer>()).Returns(mockDbSet.Object);
mockedReptryCtxt.CallBase = true;
DbSet<Customer> inMemoryDbSetCustomer = mockedReptryCtxt.Object.Set<Customer>();
In the next excerpt of code( which is our "Code Under Test"), I add a new Customer to the existing In-Memory Data, and then Invoke SaveChanges on the Mocked Object.
Customer returnCust = (Customer)(mockedReptryCtxt.Object.Set<Customer>().Add(new Customer { CustomerID = "4 ", Orders = new HashSet<Order>(), CustomerDemographics = new HashSet<CustomerDemographic>(), CompanyName = "Kolkota Knights", ContactName = "Sachin Tendulkar", ContactTitle = "current top cricket player", Address = "35 test row", City = "Kolkota", Region = "West Bengal", PostalCode = "3454534", Country = "India", Phone = "304923", Fax = "33325" }));
mockedReptryCtxt.Object.SaveChanges();
Later on in the code, I have the following excerpt of code where _context.Set() will return the In-Memory Data DBSet that we created previously
var query = _context.Set<TEntity>().AsQueryable();
if (typeof(TEntity).Name.Contains("Audit"))
{
return query;
}
if (includes != null && includes.Any())
{
foreach (var include in includes)
{
query = query.Include(include);
}
}
List<TEntity> resultsAsList = query.ToList(); // Error Thrown When using ToList()
var results = resultsAsList.AsQueryable();
When we invoke ToList(), it Throws the following Error:
System.InvalidOperationException was unhandled by user code
HResult=-2146233079
Message=Collection was modified; enumeration operation may not execute.
Source=mscorlib
StackTrace:
at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
at System.Collections.Generic.List`1.Enumerator.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at BlahBlah.Framework.EntityFramework.EntityFrameworkRepository`1.ConcreteQuery(List`1 includes) in d:\EMIS\BlahBlah Framework\BlahBlahFrameworkLightweight\BlahBlah.Framework.EntityFramework\EntityFrameworkRepository.c s:line 51
at Castle.Proxies.EntityFrameworkRepository`1Proxy.ConcreteQuery_callback(List`1 includes)
at Castle.Proxies.Invocations.EntityFrameworkRepository`1_ConcreteQuery.InvokeMethodOnTarget()
at Castle.DynamicProxy.AbstractInvocation.Proceed()
at Moq.Proxy.CastleProxyFactory.CallContext.InvokeBase()
at Moq.InvokeBase.HandleIntercept(ICallContext invocation, InterceptorContext ctx, CurrentInterceptContext localctx)
at Moq.Interceptor.Intercept(ICallContext invocation)
at Moq.Proxy.CastleProxyFactory.Interceptor.Intercept(IInvocation invocation)
at Castle.DynamicProxy.AbstractInvocation.Proceed()
at Castle.Proxies.EntityFrameworkRepository`1Proxy.ConcreteQuery(List`1 includes)
at BlahBlah.Framework.Core.Repository.BaseRepository`1.Query(List`1 includes) in d:\EMIS\BlahBlah Framework\BlahBlahFrameworkLightweight\BlahBlah.Framework.Core\Repository\BaseRepository.cs:line 149
at Castle.Proxies.EntityFrameworkRepository`1Proxy.Query_callback(List`1 includes)
at Castle.Proxies.Invocations.IRepository`1_Query.InvokeMethodOnTarget()
at Castle.DynamicProxy.AbstractInvocation.Proceed()
at Moq.Proxy.CastleProxyFactory.CallContext.InvokeBase()
at Moq.InvokeBase.HandleIntercept(ICallContext invocation, InterceptorContext ctx, CurrentInterceptContext localctx)
at Moq.Interceptor.Intercept(ICallContext invocation)
at Moq.Proxy.CastleProxyFactory.Interceptor.Intercept(IInvocation invocation)
at Castle.DynamicProxy.AbstractInvocation.Proceed()
at Castle.Proxies.EntityFrameworkRepository`1Proxy.Query(List`1 includes)
at BlahBlah.Test.Unit.CntrlrsTests.CustomerControllerTest.Test_Creation_Of_Customer_Using_Constructor_Of _Customer_Controller_That_Expects_Arguments() in d:\EMIS\BlahBlah Framework\BlahBlahFrameworkLightweight\BlahBlah.Test.Unit\CntrlrsTests\CustomerControllerTest.cs:line 278
InnerException:
What steps do we need to take in order to stop the said error from being thrown( preferably without Changing too much of our Code Under Test)?
解决方案
I found a really Clumsy Solution:
List<TEntity> tempList = new List<TEntity>();
for (int i = query.Count() - 1; i >= 0; i--)
{
tempList.Add(query.ElementAt(i));
}
List<TEntity> resultsAsList = tempList.ToList();
var results = resultsAsList.AsQueryable();
In the aforementioned code, it is important to use a for loop with an index to go through the DBSet instance. Furthermore, in the loop, you add each element to a List. ( Basically, it's important to Avoid using the Iterator)
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