我有一个像这样的xml：
<Settings>
<User default="Programmer"></User>
<Level default="2"></Level>
<Settings>
将其反序列化为UserSettings类型的对象：
[Serializable]
[XmlRoot("Settings")]
public class UserSettings
{
[XmlElement("User")]
public string User { get; set; }
[XmlElement("Level")]
public string Level { get; set; }
}
UserSettings对象提供运行时标记的值。
当标记为空或者传入的xml中没有标记时，我希望类返回默认属性值。
因此，如果存在UserSettings类型的对象objUserSettings，那么
objUserSettings.User
应该给“程序员”或xml中的默认属性值。
问候。
答案 0 :(得分：1)
试试这个
using System.ComponentModel;
[Serializable]
[XmlRoot("Settings")]
public class UserSettings
{
[DefaultValue("Yogesh")]
[XmlElement("User")]
public string User { get; set; }
[DefaultValue("1st")]
[XmlElement("Level")]
public string Level { get; set; }
}
有关详细信息，请参阅this。
答案 1 :(得分：1)
添加另一个答案，因为我对这个问题很开心。接受或离开它，但这可能是我将如何攻击此功能。
这是一个更复杂的答案，但它使用泛型为您提供类型安全性，并且大部分繁重工作都在一个基类中完成（无需反复复制/粘贴相同的代码）。
为UserSettings添加了一个属性，以显示另一种类型的示例......
[Serializable]
[XmlRoot("Settings")]
public class UserSettings
{
public UserSettings()
{
User = new DefaultableStringValue();
Level = new DefaultableIntegerValue();
IsFullscreen = new DefaultableBooleanValue();
}
[XmlElement("User")]
public DefaultableStringValue User { get; set; }
[XmlElement("Level")]
public DefaultableIntegerValue Level { get; set; }
[XmlElement("IsFullscreen")]
public DefaultableBooleanValue IsFullscreen { get; set; }
}
类型化DefaultableValues的简单实现......
[Serializable]
public class DefaultableStringValue : DefaultableValue<string>
{
public DefaultableStringValue() : base(s => s) { }
}
[Serializable]
public class DefaultableIntegerValue : DefaultableValue<int>
{
public DefaultableIntegerValue() : base(int.Parse) { }
}
[Serializable]
public class DefaultableBooleanValue : DefaultableValue<bool>
{
public DefaultableBooleanValue() : base(bool.Parse) { }
}
执行解析和缓存解析值的所有重要工作的基类...
[Serializable]
public abstract class DefaultableValue<T>
{
protected Func<string, T> _parsingFunc;
private string _valueText;
private T _cachedValue;
private bool _isValueCached;
private string _defaultText;
private T _cachedDefault;
private bool _isDefaultCached;
protected DefaultableValue(Func<string, T> parsingFunc)
{
_parsingFunc = parsingFunc;
_isValueCached = false;
_isDefaultCached = false;
}
[XmlAttribute("default")]
public string DefaultText
{
get { return _defaultText; }
set
{
_defaultText = value;
_isDefaultCached = false;
}
}
[XmlText]
public string ValueText
{
get { return _valueText; }
set
{
_valueText = value;
_isValueCached = false;
}
}
[XmlIgnore]
public T Default
{
get
{
if (_isDefaultCached)
return _cachedDefault;
if (HasDefault)
return ParseAndCacheValue(DefaultText, out _cachedDefault, out _isDefaultCached);
return default(T);
}
set
{
DefaultText = value.ToString();
_cachedDefault = value;
_isDefaultCached = true;
}
}
[XmlIgnore]
public T Value
{
get
{
if (_isValueCached)
return _cachedValue;
if (HasValue)
return ParseAndCacheValue(ValueText, out _cachedValue, out _isValueCached);
return Default;
}
set
{
ValueText = value.ToString();
_cachedValue = value;
_isValueCached = true;
}
}
[XmlIgnore]
public bool HasDefault { get { return !string.IsNullOrEmpty(_defaultText); } }
[XmlIgnore]
public bool HasValue { get { return !string.IsNullOrEmpty(_valueText); } }
private T ParseAndCacheValue(string text, out T cache, out bool isCached)
{
cache = _parsingFunc(text);
isCached = true;
return cache;
}
}
用于演示用法的示例程序......
public class Program
{
private static void Main(string[] args)
{
UserSettings userSettings = new UserSettings();
userSettings.User.Default = "Programmer";
userSettings.Level.Default = 2;
userSettings.Level.Value = 99;
XmlSerializer xmlSerializer = new XmlSerializer(typeof(UserSettings));
string serializedUserSettings;
using (StringWriter stringWriter = new StringWriter())
{
xmlSerializer.Serialize(stringWriter, userSettings);
serializedUserSettings = stringWriter.GetStringBuilder().ToString();
}
UserSettings deserializedUserSettings;
using (StringReader stringReader = new StringReader(serializedUserSettings))
{
deserializedUserSettings = (UserSettings)xmlSerializer.Deserialize(stringReader);
}
Console.Out.WriteLine("User: HasDefault={0}, Default={1}, HasValue={2}, Value={3}",
deserializedUserSettings.User.HasDefault ? "Yes" : "No",
deserializedUserSettings.User.Default,
deserializedUserSettings.User.HasValue ? "Yes" : "No",
deserializedUserSettings.User.Value);
Console.Out.WriteLine("Level: HasDefault={0}, Default={1}, HasValue={2}, Value={3}",
deserializedUserSettings.Level.HasDefault ? "Yes" : "No",
deserializedUserSettings.Level.Default,
deserializedUserSettings.Level.HasValue ? "Yes" : "No",
deserializedUserSettings.Level.Value);
Console.Out.WriteLine("IsFullscreen: HasDefault={0}, Default={1}, HasValue={2}, Value={3}",
deserializedUserSettings.IsFullscreen.HasDefault ? "Yes" : "No",
deserializedUserSettings.IsFullscreen.Default,
deserializedUserSettings.IsFullscreen.HasValue ? "Yes" : "No",
deserializedUserSettings.IsFullscreen.Value);
Console.ReadLine();
}
}
答案 2 :(得分：0)
您可以为属性使用默认值属性。
在你的情况下，它将是，
[Serializable]
[XmlRoot("Settings")]
public class UserSettings
{
[XmlElement("User")]
[DefaultValue("Programmer")]
public string User { get; set; }
[XmlElement("Level")]
[DefaultValue(2)]
public string Level { get; set; }
}
答案 3 :(得分：0)
我不相信有一种方法可以告诉字符串使用默认的xml属性。您必须将每个对象反序列化为具有默认值作为属性的结构，该属性是xml属性。
这是一个例子......
[Serializable]
[XmlRoot("Settings")]
public class UserSettings
{
[XmlElement("User")]
public DefaultableValue User { get; set; }
[XmlElement("Level")]
public DefaultableValue Level { get; set; }
}
[Serializable]
public class DefaultableValue
{
[XmlAttribute("default")]
public string Default { get; set; }
[XmlText]
public string Value { get; set; }
}
示例程序以演示用法...
public class Program
{
private static void Main(string[] args)
{
UserSettings userSettings = new UserSettings();
userSettings.User = new DefaultableValue()
{
Default = "Programmer",
Value = "Tyler"
};
userSettings.Level = new DefaultableValue()
{
Default = "2",
Value = "99"
};
XmlSerializer xmlSerializer = new XmlSerializer(typeof(UserSettings));
string serializedUserSettings;
using (StringWriter stringWriter = new StringWriter())
{
xmlSerializer.Serialize(stringWriter, userSettings);
serializedUserSettings = stringWriter.GetStringBuilder().ToString();
}
UserSettings deserializedUserSettings;
using (StringReader stringReader = new StringReader(serializedUserSettings))
{
deserializedUserSettings = (UserSettings)xmlSerializer.Deserialize(stringReader);
}
Console.Out.WriteLine("User: Default={0}, Actual={1}",
deserializedUserSettings.User.Default,
deserializedUserSettings.User.Value);
Console.Out.WriteLine("Level: Default={0}, Actual={1}",
deserializedUserSettings.Level.Default,
deserializedUserSettings.Level.Value);
}
}
（请注意，我在代码中有默认值，但它们很可能来自xml文件）