我无法使用逻辑/条件运算符确定正确的实现。我对一个应用程序有一个非常具体的要求，我一开始认为它工作正常，但是当我放到Marketplace上时，我发现我的实现根本不起作用。
按钮点击事件
中的内容如下所示//recorded count of number of saved button presses
Settings.SavedCount.Value += 1;
//both conditions must be true for the code to execute inside the 'if'
if (TrialViewModel.LicenseModeString == "Trial" && Settings.SavedCount.Value > 100)
{
MessageBoxResult result = MessageBox.Show("You have saved over 100 items! Would you like to continue?", "Congratulations", MessageBoxButton.OKCancel);
switch (result)
{
case MessageBoxResult.OK:
// A command takes a parameter and in this case we can pass null.
TrialViewModel.BuyCommand.Execute(null);
break;
case MessageBoxResult.Cancel:
return;
break;
}
}
//either the entire first condition OR the second condition must be true to execute the method ApplyAndSaveAsync()
else if((TrialViewModel.LicenseModeString == "Trial" && Settings.SavedCount.Value <= 100) || TrialViewModel.LicenseModeString == "Full")
{
ApplyAndSaveAsync();
}
当调试一切似乎工作正常时，虽然我在试用和完整模式下从市场下载后测试应用程序时，ApplyAndSaveAsync()都没有执行。需要注意的是，计数总是无限增加，但应用程序可能处于试用模式，也可能不处于试用模式。只有在试用版下载并且在用户更新之前，它才会处于试用模式，在这种情况下，其许可证将自动更改为完全模式。
编辑**
可能使用序数字符串比较而非http://msdn.microsoft.com/en-us/library/vstudio/cc165449(v=vs.110).aspx中所述的“==”。
string _license = TrialViewModel.LicenseModeString;
string _isTrial = "Trial";
// Use the overload of the Equals method that specifies a StringComparison.
// Ordinal is the fastest way to compare two strings.
bool result = _license.Equals(_isTrial, StringComparison.Ordinal);
Settings.SavedCount.Value += 1;
//both conditions must be true for the code to execute inside the 'if'
if (result && Settings.SavedCount.Value > 100)
{
MessageBoxResult result = MessageBox.Show("You have saved over 100 items! Would you like to continue?", "Congratulations", MessageBoxButton.OKCancel);
switch (result)
{
case MessageBoxResult.OK:
// A command takes a parameter and in this case we can pass null.
TrialViewModel.BuyCommand.Execute(null);
break;
case MessageBoxResult.Cancel:
return;
break;
}
}
//either the entire first condition OR the second condition must be true to execute the method ApplyAndSaveAsync()
else if((result && Settings.SavedCount.Value <= 100) || TrialViewModel.LicenseModeString == "Full")
{
ApplyAndSaveAsync();
}
另外，使用逻辑和条件AND和OR函数之间的区别是什么？我想确保评估if和if else语句中的两个语句以确保正确的过程。我的实现是否正确？
编辑2 **为试验实施添加视图模型和类助手
TrialViewModel
#region fields
private RelayCommand buyCommand;
#endregion fields
#region constructors
public TrialViewModel()
{
// Subscribe to the helper class's static LicenseChanged event so that we can re-query its LicenseMode property when it changes.
TrialExperienceHelper.LicenseChanged += TrialExperienceHelper_LicenseChanged;
}
#endregion constructors
#region properties
/// <summary>
/// You can bind the Command property of a Button to BuyCommand. When the Button is clicked, BuyCommand will be
/// invoked. The Button will be enabled as long as BuyCommand can execute.
/// </summary>
public RelayCommand BuyCommand
{
get
{
if (this.buyCommand == null)
{
// The RelayCommand is constructed with two parameters - the action to perform on invocation,
// and the condition under which the command can execute. It's important to call RaiseCanExecuteChanged
// on a command whenever its can-execute condition might have changed. Here, we do that in the TrialExperienceHelper_LicenseChanged
// event handler.
this.buyCommand = new RelayCommand(
param => TrialExperienceHelper.Buy(),
param => TrialExperienceHelper.LicenseMode == TrialExperienceHelper.LicenseModes.Trial);
}
return this.buyCommand;
}
}
public string LicenseModeString
{
get
{
return TrialExperienceHelper.LicenseMode.ToString()/* + ' ' + AppResources.ModeString*/;
}
}
#endregion properties
#region event handlers
// Handle TrialExperienceHelper's LicenseChanged event by raising property changed notifications on the
// properties and commands that
internal void TrialExperienceHelper_LicenseChanged()
{
this.RaisePropertyChanged("LicenseModeString");
this.BuyCommand.RaiseCanExecuteChanged();
}
#endregion event handlers
TrialExperienceHelper.cs
#region enums
/// <summary>
/// The LicenseModes enumeration describes the mode of a license.
/// </summary>
public enum LicenseModes
{
Full,
MissingOrRevoked,
Trial
}
#endregion enums
#region fields
#if DEBUG
// Determines how a debug build behaves on launch. This field is set to LicenseModes.Full after simulating a purchase.
// Calling the Buy method (or navigating away from the app and back) will simulate a purchase.
internal static LicenseModes simulatedLicMode = LicenseModes.Trial;
#endif // DEBUG
private static bool isActiveCache;
private static bool isTrialCache;
#endregion fields
#region constructors
// The static constructor effectively initializes the cache of the state of the license when the app is launched. It also attaches
// a handler so that we can refresh the cache whenever the license has (potentially) changed.
static TrialExperienceHelper()
{
TrialExperienceHelper.RefreshCache();
PhoneApplicationService.Current.Activated += (object sender, ActivatedEventArgs e) => TrialExperienceHelper.
#if DEBUG
// In debug configuration, when the user returns to the application we will simulate a purchase.
OnSimulatedPurchase();
#else // DEBUG
// In release configuration, when the user returns to the application we will refresh the cache.
RefreshCache();
#endif // DEBUG
}
#endregion constructors
#region properties
/// <summary>
/// The LicenseMode property combines the active and trial states of the license into a single
/// enumerated value. In debug configuration, the simulated value is returned. In release configuration,
/// if the license is active then it is either trial or full. If the license is not active then
/// it is either missing or revoked.
/// </summary>
public static LicenseModes LicenseMode
{
get
{
#if DEBUG
return simulatedLicMode;
#else // DEBUG
if (TrialExperienceHelper.isActiveCache)
{
return TrialExperienceHelper.isTrialCache ? LicenseModes.Trial : LicenseModes.Full;
}
else // License is inactive.
{
return LicenseModes.MissingOrRevoked;
}
#endif // DEBUG
}
}
/// <summary>
/// The IsFull property provides a convenient way of checking whether the license is full or not.
/// </summary>
public static bool IsFull
{
get
{
return (TrialExperienceHelper.LicenseMode == LicenseModes.Full);
}
}
#endregion properties
#region methods
/// <summary>
/// The Buy method can be called when the license state is trial. the user is given the opportunity
/// to buy the app after which, in all configurations, the Activated event is raised, which we handle.
/// </summary>
public static void Buy()
{
MarketplaceDetailTask marketplaceDetailTask = new MarketplaceDetailTask();
marketplaceDetailTask.ContentType = MarketplaceContentType.Applications;
marketplaceDetailTask.Show();
}
/// <summary>
/// This method can be called at any time to refresh the values stored in the cache. We re-query the application object
/// for the current state of the license and cache the fresh values. We also raise the LicenseChanged event.
/// </summary>
public static void RefreshCache()
{
TrialExperienceHelper.isActiveCache = CurrentApp.LicenseInformation.IsActive;
TrialExperienceHelper.isTrialCache = CurrentApp.LicenseInformation.IsTrial;
TrialExperienceHelper.RaiseLicenseChanged();
}
private static void RaiseLicenseChanged()
{
if (TrialExperienceHelper.LicenseChanged != null)
{
TrialExperienceHelper.LicenseChanged();
}
}
#if DEBUG
private static void OnSimulatedPurchase()
{
TrialExperienceHelper.simulatedLicMode = LicenseModes.Full;
TrialExperienceHelper.RaiseLicenseChanged();
}
#endif // DEBUG
#endregion methods
#region events
/// <summary>
/// The static LicenseChanged event is raised whenever the value of the LicenseMode property has (potentially) changed.
/// </summary>
public static event LicenseChangedEventHandler LicenseChanged;
#endregion events
答案 0 :(得分：0)
这可能是一个黑暗中的节目，但在某些情况下（在Java中的时间，但我不确定.NET）与“==”的字符串比较不起作用。您可以尝试使用“比较”方法而不是“==”。