c# – problem when deserializing empty xml element

Question:

have a simple hml

<doc> 
  <Dep>
    <Dprtm_code></Dprtm_code> 
    <Dprtm_name></Dprtm_name>
  </Dep>
</doc> 

the problem is that Dprtm_code can be either filled with <Dprtm_code>234234234</Dprtm_code> and not <Dprtm_code></Dprtm_code> . created a schema:

//...
<xs:element type="xs:long" name="Dprtm_code" nillable="true"/>
<xs:element type="xs:string" name="Dprtm_name"/>
//...

created a class and described these fields in it:

//...
private long? dprtm_codeField;    
private string dprtm_nameField;

[XmlElementAttribute(IsNullable=true)]
public long? Dprtm_code {
    get {
        return this.dprtm_codeField;
    }
    set {
        this.dprtm_codeField = value;
    }
}
public string Dprtm_name {
    get {
        return this.dprtm_nameField;
    }
    set {
        this.dprtm_nameField = value;
    }
}
//...

but when deserializing hml with an empty code <Dprtm_code></Dprtm_code> , a type conversion error occurs. actually the question: how to correctly declare elements that can be empty in xml?

Answer:

The Xml corresponding to the given schema and deserializing into the given class should look like this:

<?xml version="1.0" encoding="UTF-8"?>
<doc xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Dep>
    <Dprtm_code xsi:nil="true"></Dprtm_code>
    <Dprtm_name></Dprtm_name>
  </Dep>
</doc>

That is, there must be a nil attribute from the specified namespace. It is handled correctly by the XmlSerializer (I believe it is used).

On serialization, the xsi:nil attribute will be added automatically as needed.

Schema validation also fails without this attribute.