无法将System.String强制转换为System.Collections.Generic.Dictionary类型 <string, string> 与会话变量

Question

Hi all and thanks in advance. I have some code I'm trying to fix where I'm getting the

error message: Unable to cast System.String to type System.Collections.Generic.Dictionary<string, string>

but I can't figure out which portion of the code is being interpreted as a System.String and being inserted into the session variable causing the cast to Dictionary<string, string> to break.

The code is fairly simple, this declaration:

  Dictionary<string, string> myControls; 
  private readonly string SCONTROLS = "smControls";

In OnInit:

  if(!isPostBack)
  {
      myControls = new Dictionary<string, string>();
      Session[SCONTROLS] = myControls;
  }
  else
  {
      if (Session[SCONTROLS] != null)
        {
            myControls = (Dictionary<string,string>)Session[SCONTROLS];

            if (myControls != null)
                foreach (var controlID in myControls.Keys)
                {
                    UserControl controlToAdd = new UserControl();
                    controlToAdd = (UserControl)controlToAdd.LoadControl(myControls[controlID]);
                    controlToAdd.ID = controlID;

                    formatPlaceHolder(controlToAdd);
                }
        }
  }

Then in a separate section where there is a control, some of the values are being updated:

  UserControl uc = DefaultControl as UserControl;
  if (uc != null)
    {
        uc.ID = Guid.NewGuid().ToString();
        formatPlaceHolder(uc);
        if (!myControls.Keys.Contains(uc.ID))
            myControls.Add(uc.ID, uc.AppRelativeVirtualPath);
        else
            myControls[uc.ID] = uc.AppRelativeVirtualPath;

        DefaultControl.LoadNewItem(item, uc.ID, Master.EmpID.Value, ShowRemove, Master.ID);

    }

I have speculated that maybe part of the problem is that when myControls is altered it's never saved into the Session variable so when it tries to do the cast from the Session variable is basically just empty. But since it was initialized as a Dictionary<string,string> object to start with I would think it wouldn't matter if it were still empty?

Or is the problem that it isn't initializing properly inside the OnInit function?

Updating information:

The values in the Session variable look like this:

 Key: c52acd20-8d3e-44cc-bc79-8fee9c9c3064
 Value: "~/Questions.ascx"

Answer 1

Did you put quote around string intentionally? I think it should be, myControls = (Dictionary)Session[SCONTROLS];