Web services 如何在SoapUI模拟服务中处理WSDL文件中的nillable

正在尝试生成模拟SOAP服务，但出现错误

WSDLException (at /definitions/message[23]/part[1]): faultCode=INVALID_WSDL: 
Encountered illegal extension attribute 'nillable'. 
Extension attributes must be in a namespace other than WSDL's

这看起来是因为元素

<part name="ChangesSince" nillable="true" type="xs:dateTime" />

而与实际的web服务相比，它们生成为

[System.Xml.Serialization.SoapElementAttribute(IsNullable=true)]
public System.Nullable<System.DateTime> ClosureDate 

[System.Xml.Serialization.SoapElementAttribute（IsNullable=true）]
公共系统。可为空的ClosureDate

有没有办法处理SoapUI中的nillable

[System.Xml.Serialization.SoapElementAttribute(IsNullable=true)]
public System.Nullable<System.DateTime> ClosureDate