为什么将字符串转换为Int32在网站中随机失败

Question

I have some piece of code which fails at times due to error System.FormatException . In my understanding if the UserId is not empty then default 0 should be returned from below method GetUserProperty and I know (and have not doubt on this) that UserId in the system will be either some number or empty, it will never be anything non-numeric.

Code as below:

private void SomeMethod()
{
    var userId = Convert.ToInt32(GetUserProperty("UserId", "0"));
    // Do something with userId..
}

public string GetUserProperty(string propertyName, string defaultValue = "")
{
    var propertyValue = SecurityUtil.GetUserProperty(propertyName);
    return !string.IsNullOrWhiteSpace(propertyValue) ? propertyValue : defaultValue;
}

StackTrace in the system log says:

System.FormatException: Input string was not in a correct format. at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) at ...

Answer 1

Probably SecurityUtil.GetUserProperty(propertyName) is returning a value that cannot be parsed into an int.

modify SomeMethod() like this

private void SomeMethod()
{
  int userId = 0;
  string userProperty = GetUserProperty("UserId", "0");

  if(int.TryParse(userProperty , out userId)){
      // Do something with userId..
  }
  else{
    //Do something with the exception
      //Console.Write("Invalid property value {0}", userProperty);
//Sitecore.Diagnostics.Log.Info("Invalid property value " + userProperty.ToString(), this);
  }
}

Answer 2

Welcome to an world where not everyone shares the same alphabet.

CurrentCulture is probably the UI culture in your case and therefore unreliable. It might be f.ex. chinese depending on your user :-)

The better way to handle this is to explicitly set the culture.

int value;
if (!int.TryParse(GetUserProperty("UserId", "0"), 
    NumberStyles.Any, CultureInfo.InvariantCulture, out value))
{
   // make / throw your own error message with details on the user property!
}

Answer 3

Try to change your method like this:

public string GetUserProperty(string propertyName, string defaultValue = "")
{
    var propertyValue = SecurityUtil.GetUserProperty(propertyName);
    return Array.TrueForAll(propertyValue .ToCharArray(), c => Char.IsDigit(c)) ? propertyValue : defaultValue;
}

Answer 4

Very probably it's the GetUserPropery which returns an invalid integer. Try this ( if your value can be like 23.5, use a Regex instead to validate the string ):

private void SomeMethod()
{
    var userIdStr =GetUserProperty("UserId", "0");
    Debug.Assert(userIdStr.All(char.IsDigit));
    var userId = Convert.ToInt32(userIdStr);
    // Do something with userId..
}

Or put a breakpoint with a Condition using Int.TryParse.

Answer 5

The error cause is the SecurityUtil.GetUserProperty() method, because maybe its not convertible to Convert.ToInt32() .

public string GetUserProperty(string propertyName, string defaultValue = "")
{
    var propertyValue = SecurityUtil.GetUserProperty(propertyName); // Why used var maybe because its not convertible to integer?
    return !string.IsNullOrWhiteSpace(propertyValue) ? propertyValue : defaultValue; // If this is true and propertyValue is not convertible to Int32, System.FormateException will be occurred.
}

Just like example in my fiddle: http://goo.gl/GMP5tH