Serialize a nullable int


Question

I have a class with a nullable int? datatype set to serialize as an xml element. Is there any way to set it up so the xml serializer will not serialize the element if the value is null?

I've tried to add the [System.Xml.Serialization.XmlElement(IsNullable=false)] attribute, but I get a runtime serialization exception saying there was a an error reflecting the type, because "IsNullable may not be set to 'false' for a Nullable type. Consider using 'System.Int32' type or removing the IsNullable property from the XmlElement attribute."

[Serializable]
[System.Xml.Serialization.XmlRoot("Score", Namespace = "http://mycomp.com/test/score/v1")]
public class Score
{
    private int? iID_m;
    ...

    /// <summary>
    /// 
    /// </summary>        
    public int? ID 
    { 
        get 
        { 
            return iID_m; 
        } 
        set 
        { 
            iID_m = value; 
        } 
    }
     ...
}

The above class will serialize to:

<Score xmlns="http://mycomp.com/test/score/v1">
    <ID xsi:nil="true" />
</Score>

But for IDs that are null I don't want the ID element at all, primarily because when I use OPENXML in MSSQL, it returns a 0 instead of null for an element that looks like

1
87
12/20/2016 4:46:39 AM

Accepted Answer

XmlSerializer supports the ShouldSerialize{Foo}() pattern, so you can add a method:

public bool ShouldSerializeID() {return ID.HasValue;}

There is also the {Foo}Specified pattern - not sure if XmlSerializer supports that one.

147
10/29/2008 10:38:54 AM

I'm using this micro-pattern to implement Nullable serialization:

[XmlIgnore]
public double? SomeValue { get; set; }

[XmlAttribute("SomeValue")] // or [XmlElement("SomeValue")]
[EditorBrowsable(EditorBrowsableState.Never)]
public double XmlSomeValue { get { return SomeValue.Value; } set { SomeValue= value; } }  
[EditorBrowsable(EditorBrowsableState.Never)]
public bool XmlSomeValueSpecified { get { return SomeValue.HasValue; } }

This provides the right interface to the user without compromise and still does the right thing when serializing.


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