我收到了InvalidCastException
,我不明白为什么。
以下是引发异常的代码:
public static void AddToTriedList(string recipeID)
{
IList<string> triedIDList = new ObservableCollection<string>();
try
{
IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;
if (!settings.Contains("TriedIDList"))
{
settings.Add("TriedIDList", new ObservableCollection<Recipe>());
settings.Save();
}
else
{
settings.TryGetValue<IList<string>>("TriedIDList", out triedIDList);
}
triedIDList.Add(recipeID);
settings["TriedIDList"] = triedIDList;
settings.Save();
}
catch (Exception e)
{
Debug.WriteLine("Exception while using IsolatedStorageSettings in AddToTriedList:");
Debug.WriteLine(e.ToString());
}
}
AppSettings.cs:(摘录)
// The isolated storage key names of our settings
const string TriedIDList_KeyName = "TriedIDList";
// The default value of our settings
IList<string> TriedIDList_Default = new ObservableCollection<string>();
...
/// <summary>
/// Property to get and set the TriedList Key.
/// </summary>
public IList<string> TriedIDList
{
get
{
return GetValueOrDefault<IList<string>>(TriedIDList_KeyName, TriedIDList_Default);
}
set
{
if (AddOrUpdateValue(TriedIDList_KeyName, value))
{
Save();
}
}
}
GetValueOrDefault<IList<string>>(TriedIDList_KeyName, TriedIDList_Default)
和AddOrUpdateValue(TriedIDList_KeyName, value)
是Microsoft推荐的常用方法;你可以找到完整的代码here。
settings.TryGetValue<IList<string>>("TriedIDList", out triedIDList);
答案 0 :(得分:3)
您正在向ObservableCollection<Recipe>
添加settings
:
settings.Add("TriedIDList", new ObservableCollection<Recipe>());
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
但是你要读回IList<string>
,这显然是另一种类型:
settings.TryGetValue<IList<string>>("TriedIDList", out triedIDList);
// ^^^^^^^^^^^^^
您对triedIDList
的声明如下:
IList<string> triedIDList = new ObservableCollection<string>();
// ^^^^^^^^^^^^^ // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
首先,决定一种类型,然后在所有这些地方使用完全相同的类型(即使你认为这不是绝对必要的),然后看看InvalidCastException
是否消失。