从Session状态检索字典时，我得到System.InvalidCastException

Question

[A]System.Collections.Generic.Dictionary 2[System.String,System.Collections.Generic.List 1[DisplayAllQuestionsTable]] cannot be cast to [B]System.Collections.Generic.Dictionary 2[System.String,System.Collections.Generic.List 1[DisplayAllQuestionsTable]]. Type A originates from 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in the context 'LoadNeither' at location

My Dictionary syntax:

Dictionary<string, List<DisplayAllQuestionsTable>> tPages=tPages = 
   new Dictionary<string, List<DisplayAllQuestionsTable>>();

When i try to retrieve it from Session:

tPages = (Dictionary<string, List<DisplayAllQuestionsTable>>)Session["ThreadPage"]; // i get an exception here

Unable to cast object of type [

System.String

,System.Collections.Generic.List 1[DisplayAllQuestionsTable]]' to type '**System.Collection**s.Generic.Dictionary 2

Answer 1

尝试获取Session [“ThreadPage”]对象的类型：

Session["ThreadPage"].GetType().ToString();

Answer 2

Do you have two different DisplayAllQuestionsTable versions of this type?

Qualify the DisplayAllQuestionsTable type name with namespace.

Ex:

// Creating the instance..
Dictionary<string, List<SampleAppNamespace.DisplayAllQuestionsTable>> tPages = 
   new Dictionary<string, List<SampleAppNamespace.DisplayAllQuestionsTable>>();

// putting it into session
Session["ThreadPage"] = tPages;

// reading back from session
tPages = Session["ThreadPage"] as Dictionary<string, List<SampleAppNamespace.DisplayAllQuestionsTable>>;