Question

我有以下代码：

List<Type> p1 = new List<Type>();
p1.Add(typeof(int));
p1.Add(typeof(string));
dynamic genericDic = typeof(Dictionary<, >);
dynamic specificDic1 = genericDic.MakeGenericType(p1.ToArray());
dynamic dic1 = Activator.CreateInstance(specificDic1);
dic1.Add(1, "John");
dic1.Add(2, "Smith");
dynamic genericLst = typeof(List<>);
dynamic specificLst = genericLst.MakeGenericType(typeof(string));
dynamic list = Activator.CreateInstance(specificLst);
list.AddRange(dic1.Values.ToList());

当我尝试执行list.AddRange(dic1.Values.ToList());时，我得到以下异常

未找到类型'ValueCollection'上的公共成员'ToList'。

堆栈追踪：

   at Microsoft.VisualBasic.CompilerServices.Symbols.Container.GetMembers(String& MemberName, Boolean ReportErrors)
   at Microsoft.VisualBasic.CompilerServices.NewLateBinding.ObjectLateGet(Object Instance, Type Type, String MemberName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack)
   at Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateGet(Object Instance, Type Type, String MemberName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack)
   at StyleResearch.DataManagement.DataStream.Business.MonthEndProcess.ConverToLegacyStructureInMemory(List`1 marketDataTypeIds, String tableName, Int32 placeHolderValue) in C:\Style Research\Work\SRDM\trunk\StyleResearch.DataManagement.DataStream.Business\MonthEndProcess.vb:line 1850
   at StyleResearch.DataManagement.DataStream.UI.DDLMonthEndProcess._Lambda$__6(LegacyStructureDetail legacy) in C:\Style Research\Work\SRDM\trunk\StyleResearch.DataManagement.DataStream.UI\DDLMonthEndProcess.vb:line 1198
   at System.Threading.Tasks.Parallel.<>c__DisplayClass2d`2.<ForEachWorker>b__23(Int32 i)
   at System.Threading.Tasks.Parallel.<>c__DisplayClassf`1.<ForWorker>b__c()

注意：我已经通过VB.NET示例转换为C＃，但堆栈跟踪来自VB.NET项目

当我这样做时，它的工作非常好：

Dictionary<int, string> dic = new Dictionary<int, string>();
dic.Add(1, "John");
dic.Add(2, "Smith");
List<string> lst = new List<string>();
lst.AddRange(dic.Values.ToList());

Answer 1

投下它：

list.AddRange(((IEnumerable<string>)dic1.Values).ToList());

此外，您可以再次通过动态：

list.AddRange((dynamic)dic1.Values));

Answer 2

ToList＆lt; T＆gt;（）是IEnumerable＆lt; T＆gt;的扩展方法。但你的dic1.Values是动态类型而不是IENumerable＆lt; string＆gt;所以.Net找不到并使用这种扩展方法。你可以尝试简单的foreach：

foreach (var value in dic1.Values)
  list.Add(value)

Answer 3

list.AddRange((IEnumerable<string>)dic.Values))

或

List<string> list = ((IEnumerable<string>)dic.Values).ToList();

或

List<string> list = new List<string>((IEnumerable<string>)dic.Values);

Answer 4

尝试使用无扩展函数语法进行调用，例如

Enumerable.ToList ( (dynamic) dic1.Values )

DLR不会在运行时搜索继承接口的扩展功能（出于性能原因或避免含糊不清，我猜）。

如何将动态字典值转换为列表？

4 个答案: