抑制XmlSerializer发出的空值类型

Question

请考虑以下Amount值类型属性,该属性标记为可为空的XmlElement:

[XmlElement(IsNullable=true)] 
public double? Amount { get ; set ; }

当可空值类型设置为null时,C#XmlSerializer结果如下所示:

<amount xsi:nil="true" />

我希望XmlSerializer能够完全抑制元素,而不是发出这个元素.为什么？我们使用Authorize.NET进行在线支付,如果存在此null元素,Authorize.NET会拒绝该请求.

当前的解决方案/解决方法是根本不序列化Amount值类型属性.相反,我们创建了一个互补属性SerializableAmount,它基于Amount而是序列化的.由于SerializableAmount的类型为String,默认情况下,如果默认为null,则XmlSerializer会抑制类似引用类型的引用类型,一切都很有效.

/// <summary>
/// Gets or sets the amount.
/// </summary>
[XmlIgnore]
public double? Amount { get; set; }

/// <summary>
/// Gets or sets the amount for serialization purposes only.
/// This had to be done because setting value types to null 
/// does not prevent them from being included when a class 
/// is being serialized.  When a nullable value type is set 
/// to null, such as with the Amount property, the result 
/// looks like: &gt;amount xsi:nil="true" /&lt; which will 
/// cause the Authorize.NET to reject the request.  Strings 
/// when set to null will be removed as they are a 
/// reference type.
/// </summary>
[XmlElement("amount", IsNullable = false)]
public string SerializableAmount
{
    get { return this.Amount == null ? null : this.Amount.ToString(); }
    set { this.Amount = Convert.ToDouble(value); }
}

当然,这只是一种解决方法.有没有更简洁的方法来抑制空值类型元素被发射？

Answer 1

尝试添加:

public bool ShouldSerializeAmount() {
   return Amount != null;
}

框架的某些部分可识别出许多模式.有关信息,XmlSerializer也寻找public bool AmountSpecified {get;set;}.

完整示例(也切换到decimal):

using System;
using System.Xml.Serialization;

public class Data {
    public decimal? Amount { get; set; }
    public bool ShouldSerializeAmount() {
        return Amount != null;
    }
    static void Main() {
        Data d = new Data();
        XmlSerializer ser = new XmlSerializer(d.GetType());
        ser.Serialize(Console.Out, d);
        Console.WriteLine();
        Console.WriteLine();
        d.Amount = 123.45M;
        ser.Serialize(Console.Out, d);
    }
}

有关MSDN上ShouldSerialize*的更多信息.

Answer 2

还有另一种选择

 <amount /> instead of <amount xsi:nil="true" />

使用

[XmlElement("amount", IsNullable = false)]
public string SerializableAmount
{
    get { return this.Amount == null ? "" : this.Amount.ToString(); }
    set { this.Amount = Convert.ToDouble(value); }
}