规划步骤 3：确定每个实体的标识符
上次修改时间： 2010年4月19日
适用范围： SharePoint Server 2010
对于每个外部内容类型，必须指定用于唯一标识该外部内容类型的实例的字段。如果没有标识符，Business Data Connectivity (BDC) Service 将无法唯一标识实体实例。后端应用程序方法返回的数据只是没有标识符的 Blob 数据。只有返回的数据具有标识符，这些数据在 BDC 中才有语义意义，只有这样您才能对这些实体执行操作、进行搜索和爬网。
例如，SampleWebService 代理中的 Customer 类包含一个名为 CustomerID 的字段，该字段唯一标识一个客户实例。因此，CustomerID 可用作 Customer 外部内容类型的标识符。以下是 Web 服务代理中的 Customer 类定义。
public partial class Customer {
private string customerIDField;
private string nameField;
private System.Nullable<long> workPhoneNumberField;
private System.Nullable<long> mobilePhoneNumberField;
private string industryField;
private string webSiteField;
private CustomerAddress[] customerAddressesField;
private string parentCustomerIDField;
/// <remarks/>
public string CustomerID { get { return this.customerIDField; } set { this.customerIDField = value; }
}
/// <remarks/>
public string Name {
get {
return this.nameField;
}
set {
this.nameField = value;
}
}
/// <remarks/>
[System.Xml.Serialization.XmlElementAttribute(IsNullable=true)]
public System.Nullable<long> WorkPhoneNumber {
get {
return this.workPhoneNumberField;
}
set {
this.workPhoneNumberField = value;
}
}
/// <remarks/>
[System.Xml.Serialization.XmlElementAttribute(IsNullable=true)]
public System.Nullable<long> MobilePhoneNumber {
get {
return this.mobilePhoneNumberField;
}
set {
this.mobilePhoneNumberField = value;
}
}
/// <remarks/>
public string Industry {
get {
return this.industryField;
}
set {
this.industryField = value;
}
}
/// <remarks/>
public string WebSite {
get {
return this.webSiteField;
}
set {
this.webSiteField = value;
}
}
/// <remarks/>
public CustomerAddress[] CustomerAddresses {
get {
return this.customerAddressesField;
}
set {
this.customerAddressesField = value;
}
}
/// <remarks/>
public string ParentCustomerID {
get {
return this.parentCustomerIDField;
}
set {
this.parentCustomerIDField = value;
}
}
}
public Customer(string id, string name, uint? workphone, uint? mobilephone, string industry, string website, CustomerAddress[] custaddresses, string parentid)
{
this.CustomerID = id;
this.Name = name;
this.WorkPhoneNumber = workphone;
this.MobilePhoneNumber=mobilephone;
this.Industry = industry;
this.WebSite = website;
this.CustomerAddresses = custaddresses;
this.ParentCustomerID = parentid;
}
}
但是，对于 LineItem 类，OrderID 和 ProductID 共同标识 LineItem 示例。因此，可声明 OrderID 和 ProductID 作为 LineItem 外部内容类型的标识符，如以下代码示例中所示。
public partial class LineItem {
private string orderIDField;
private string productIDField;
private string productNameField;
private int orderQtyField;
private decimal unitPriceField;
private decimal lineTotalField;
/// <remarks/>
public string OrderID { get { return this.orderIDField; } set { this.orderIDField = value; } }
/// <remarks/>
public string ProductID { get { return this.productIDField; } set { this.productIDField = value; } }
/// <remarks/>
public string ProductName {
get {
return this.productNameField;
}
set {
this.productNameField = value;
}
}
/// <remarks/>
public int OrderQty {
get {
return this.orderQtyField;
}
set {
this.orderQtyField = value;
}
}
/// <remarks/>
public decimal UnitPrice {
get {
return this.unitPriceField;
}
set {
this.unitPriceField = value;
}
}
/// <remarks/>
public decimal LineTotal {
get {
return this.lineTotalField;
}
set {
this.lineTotalField = value;
}
}
}
然而，有可能出现某个外部内容类型无需标识符的情况，例如，SampleWebService 代理中的 Address 外部内容类型。Address 外部内容类型没有标识符，因为我们只希望显示客户的地址列表。这意味着它只是 Blob 数据；您无法对该外部内容类型运行操作，无法使用外部内容类型实例选取器，无法与该外部内容类型关联，无法对该外部内容类型进行搜索或爬网等。
public partial class CustomerAddress {
private CustomerStreet streetField;
private string cityField;
private States stateProvinceField;
private string countryRegionField;
private string postalCodeField;
/// <remarks/>
public CustomerStreet Street {
get {
return this.streetField;
}
set {
this.streetField = value;
}
}
/// <remarks/>
public string City {
get {
return this.cityField;
}
set {
this.cityField = value;
}
}
/// <remarks/>
public States StateProvince {
get {
return this.stateProvinceField;
}
set {
this.stateProvinceField = value;
}
}
/// <remarks/>
public string CountryRegion {
get {
return this.countryRegionField;
}
set {
this.countryRegionField = value;
}
}
/// <remarks/>
public string PostalCode {
get {
return this.postalCodeField;
}
set {
this.postalCodeField = value;
}
}
}