[NHibernate] Nullables

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[NHibernate] Isessionfactory Configuration

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[NHibernate] O/R Mapping Basics

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[NHibernate] NHibernate.Tool.hbm2net

What is Nullables?

Nullables is an add-on software for Nhibrnate, which is a contribution of Donald L Mull Jr (aka luggage), and most database systems allow the base type (int or bool) to be null. This means that a boolean column may have 0, 1, or null values, and null and 0 have different meanings. But in. NET 1.x this is not possible; a bool is either TRUE or false.

Nullables makes possible the basic types of nullable in Nhibernae. Attention. NET2.0 already has this feature.

How to use?

This is a simple example, it uses Nullables.nullabledatetime to (optionally) save a person's birthday.

1  Public class Person2 {3     int_id;4     string_name;5 nullables.nullabledatetime _dateofbirth;6      PublicPerson ()7     {8     }9      Public intIdTen     { One         Get{return  This. _id;} A     } -      Public stringName -     { the         Get{return  This. _name;} -         Set{ This. _name =value;} -     } -      Publicnullables.nullabledatetime dateOfBirth +     { -         Get{return  This. _dateofbirth;} +         Set{ This. _dateofbirth =value;} A     } at}

As you can see, dateOfBirth is the Nullables.nullabledatetime type (not System.DateTime). Here is the map

1 <?XML version= "1.0" encoding= "Utf-8"?> 2 <hibernate-mappingxmlns= "urn:nhibernate-mapping-2.0">3     <classname= "Example.person, Example"Table= "Person">4         <IDname= "Id"Access= "Field.camelcase-underscore"Unsaved-value= "0">5             <Generatorclass= "Native" />6         </ID>7         < Propertyname= "Name"type= "String"length= "$" />8         < Propertyname= "dateOfBirth"type= "Nullables.NHibernate.NullableDateTimeType, nullables.nhibernate" />9     </class>Ten </hibernate-mapping>

Focus

In this mapping, the type of dateOfBirth must be Nullables.NHibernate.NullableDateTimeType. Note that NHibernate.Mapping.Attributes will handle it automatically.
Nullables.NHibernate.NullableXXXType is the wrapper class used to convert the Nullables type to the database.

Here is a partial code for this example:

1Person per =NewPerson ();2TextBox1.Text = per. DateOfBirth.Value.ToString ()//Would throw a exception when there is no value.3TextBox1.Text = per. Dateofbirth.tostring ()//would work . It'll return an empty string if there is no value.4TextBox1.Text = (per. Dateofbirth.hasvalue? Per. DateOfBirth.Value.ToShortDateString ():"Unknown")//Friendly Message5Per. dateOfBirth =NewSystem.DateTime (1979, One,8);//implicit cast from the "plain" System.DateTime.6Per. dateOfBirth =NewNullabledatetime (NewSystem.DateTime (1979, One,8));//The long.7Per. dateOfBirth =NULL;//This works.8Per. dateOfBirth = Nullabledatetime.default;//This is more correct.

This article is from "NHibernate Chinese document"