Defining column

SharePoint columns are specified by annotating properties with derived classes of the SPFieldAttribute attribute class.

To implement the property use data getter and setter methods provided by the protected member SPModel.Adapter:

[SPContentType("0x01005A132C01F46341319BBA6C776A2D9D32", "My Item")]
public class MyItem : SPModel {
    [SPTextField("MyRichDescription", Title = "Description")]
    public string Description {
      	get { return Adapter.GetString("MyRichDescription"); }
        set { Adapter.SetString("MyRichDescription", value); }
    }
}

For most cases, if the getter or setter is just simple data read/write to the specified field, you can mark both the class and the property to be abstract. The library will take care for you.

[SPContentType("0x01005A132C01F46341319BBA6C776A2D9D32", "My Item")]
public class MyItem : SPModel {
    [SPTextField("MyRichDescription", Title = "Description")]
    public abstract string Description { get; set; }
}

Choosing attribute and property type

When declaring properties on the model class, make sure the attribute type and property type matches with the field type.

Note: When getting or setting values on properties that does not match with the field types of corresponding fields, the adapter will to parse the value in the retrieved format. However, it is advised to keep field type, attribute type and property type in sync.

Field Type	Attribute Type	Property Type	Adapter Method
Integer	SPIntegerFieldAttribute	int	GetInteger
Number	SPNumberFieldAttribute	double	GetDouble
Currency	SPCurrencyFieldAttribute	double	GetDouble
Text	SPTextFieldAttribute	string	GetString
Url	SPUrlFieldAttribute	SPFieldUrlValue string	GetUrlFieldValue GetString
Note	SPNoteFieldAttribute	string	GetString
Boolean	SPBooleanFieldAttribute	bool	GetBoolean
Guid	SPGuidFieldAttribute	Guid	GetGuid
DateTime	SPDateTimeFieldAttribute	DateTime? DateTime	GetDateTime GetDateOnly
Choice	SPChoiceFieldAttribute	Enum	GetEnum<T>
MultiChoice	SPMultiChoiceFieldAttribute	Enum IList<string> ReadOnlyCollection<string>	GetEnum<T> GetMultiChoiceFieldValue GetMultiChoiceFieldValueReadOnly
Lookup	SPLookupFieldAttribute	string IList<string> ReadOnlyCollection<string> T IList<T> ReadOnlyCollection<T>	GetLookupFieldValue GetMultiLookupFieldValue GetMultiLookupFieldValueReadOnly GetModel<T> GetModelCollection<T> GetModelCollectionReadOnly<T>
User	SPUserFieldAttribute	SPPrincipal IList<SPPrincipal> ReadOnlyCollection<SPPrincipal>	GetUserFieldValue GetMultiUserFieldValue GetMultiUserFieldValueReadOnly
Taxonomy	TaxonomyFieldAttribute	Term IList<Term> ReadOnlyCollection<Term>	GetTaxonomy GetTaxonomyMulti GetTaxonomyMultiReadOnly
HTML	PublishingHtmlFieldAttribute	string	GetString
Image	PublishingImageFieldAttribute	string	GetString

Built-in or third-party columns

When associating built-in or third-party columns, use SPBuiltInFieldAttribute as the attribute type regardless of the field types.

When such association is encountered, the built-in or third-party columns will not be modified in site or web level.

[SPContentType("0x01005A132C01F46341319BBA6C776A2D9D32", "My Item")]
public abstract class MyItem : SPModel {
    // "Title" column is a built-in column
    // use `SPBuiltInFieldAttribute` even though we know it is a Text column
    
    // set "Title" column in this content type as a required column
    // this only affects "Title" column under lists that 
    // are provisioned with this content type
    // the site column definition of the "Title" column is unchanged
    [SPBuiltInField(BuiltInFieldNames.Title,
         Required = SPOption.True)]
    public abstract string Title { get; set; }
}

Form Visibility

This refers to on which forms the column is visible to users.

Value	Display Form	Edit Form	New Form	Version History
Visible	Yes	Yes	Yes	Yes
ExceptEditForm	Yes	No	Yes	Yes
ExceptNewForm	Yes	Yes	No	Yes
DisplayOnly	Yes	No	No	Yes
Hidden	No	No	No	No