MyORM的使用(一)

 之前把自己写过的一个简单ORM类库介绍了下，考虑到代码会有改动而blog中编辑代码太麻烦，在CodePlex上建了一个项目：MyORM，相关代码和文件维护起来方便不少。

CodePlex下载地址http://www.codeplex.com/MyOrm/Release/ProjectReleases.aspx?ReleaseId=18323，包含了源码、一个Sample工程和CodeSmith的模板文件。

简单说一下自己写ORM的目的，个人不喜欢把实体对象搞得太复杂，因为在系统中实体是作为数据载体存在的，如果还要让它负责数据库操作、实体关系，往往会造成很多问题。

另外就是现有的ORM并不是太好用，比如说在显示到界面时不方便，或者效率太低，我的方法是给实体类型定义一个View用来显示。还有查询也不是很好用，我的想法是简单的查询可以定义统一的查询方式，复杂的查询通过自己写SQL然后封装成方法，如果复杂的查询还要定义成统一的方式那就另外自己开发吧。

 

以Northwind的数据库做例子，实体的定义可能是下面这样：

1.     [Table("Products")]
2.     [Serializable]
3.     public class Products 
4.     {
5.         #region Member Variables        
6.         private int productID;
7.         private string productName;
8.         private int? supplierID;
9.         private int? categoryID;
10.         private string quantityPerUnit;
11.         private decimal? unitPrice;
12.         private short? unitsInStock;
13.         private short? unitsOnOrder;
14.         private short? reorderLevel;
15.         private bool discontinued;
16.         #endregion
18.         #region Public Properties
19.         [Column(IsPrimaryKey = true)]
20.         public int ProductID
21.         {
22.             get { return productID; }           
23.             set { productID = value; }
24.         }
25.         
26.         [Column]
27.         public string ProductName
28.         {
29.             get { return productName; }         
30.             set { productName = value; }
31.         }
32.         
33.         [Column]
34.         public int? SupplierID
35.         {
36.             get { return supplierID; }          
37.             set { supplierID = value; }
38.         }
39.         
40.         [Column]
41.         public int? CategoryID
42.         {
43.             get { return categoryID; }          
44.             set { categoryID = value; }
45.         }
46.         
47.         [Column]
48.         public string QuantityPerUnit
49.         {
50.             get { return quantityPerUnit; }         
51.             set { quantityPerUnit = value; }
52.         }
53.         
54.         [Column]
55.         public decimal? UnitPrice
56.         {
57.             get { return unitPrice; }           
58.             set { unitPrice = value; }
59.         }
60.         
61.         [Column]
62.         public short? UnitsInStock
63.         {
64.             get { return unitsInStock; }            
65.             set { unitsInStock = value; }
66.         }
67.         
68.         [Column]
69.         public short? UnitsOnOrder
70.         {
71.             get { return unitsOnOrder; }            
72.             set { unitsOnOrder = value; }
73.         }
74.         
75.         [Column]
76.         public short? ReorderLevel
77.         {
78.             get { return reorderLevel; }            
79.             set { reorderLevel = value; }
80.         }
81.         
82.         [Column]
83.         public bool Discontinued
84.         {
85.             get { return discontinued; }            
86.             set { discontinued = value; }
87.         }
88.         
89.         #endregion
90.     }

而在显示到界面的时候直接显示SupplierID和CategoryID是不合适的，而应该显示对应对象的名称或者其他内容，因此需要再定义一个View：

1.     [TableJoin(typeof(Categories), "CategoryID", AliasName = ProductsView.Category)]
2.     [TableJoin(typeof(Suppliers), "SupplierID", AliasName = ProductsView.Supplier)]
3.     public class ProductsView : Products
4.     {
5.         #region Constant        
6.         public const string Category = "Category";
7.         public const string Supplier = "Supplier";
8.         #endregion
9.         
10.         #region Member Variables        
11.         private string category_CategoryName;           
12.         private string category_Description;            
13.         private byte[] category_Picture;            
14.         private string supplier_CompanyName;            
15.         private string supplier_ContactName;            
16.         private string supplier_ContactTitle;           
17.         private string supplier_Address;            
18.         private string supplier_City;           
19.         private string supplier_Region;         
20.         private string supplier_PostalCode;         
21.         private string supplier_Country;            
22.         private string supplier_Phone;          
23.         private string supplier_Fax;            
24.         private string supplier_HomePage;           
25.         #endregion
27.         #region Public Properties
28.         [Column("CategoryName", Foreign = ProductsView.Category, ColumnMode = ColumnMode.Read)]
29.         public string Category_CategoryName
30.         {
31.             get { return category_CategoryName; }           
32.             set { category_CategoryName = value; }
33.         }
34.         
35.         [Column("Description", Foreign = ProductsView.Category, ColumnMode = ColumnMode.Read)]
36.         public string Category_Description
37.         {
38.             get { return category_Description; }            
39.             set { category_Description = value; }
40.         }
41.         
42.         [Column("Picture", Foreign = ProductsView.Category, ColumnMode = ColumnMode.Read)]
43.         public byte[] Category_Picture
44.         {
45.             get { return category_Picture; }            
46.             set { category_Picture = value; }
47.         }
48.         
49.         [Column("CompanyName", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
50.         public string Supplier_CompanyName
51.         {
52.             get { return supplier_CompanyName; }            
53.             set { supplier_CompanyName = value; }
54.         }
55.         
56.         [Column("ContactName", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
57.         public string Supplier_ContactName
58.         {
59.             get { return supplier_ContactName; }            
60.             set { supplier_ContactName = value; }
61.         }
62.         
63.         [Column("ContactTitle", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
64.         public string Supplier_ContactTitle
65.         {
66.             get { return supplier_ContactTitle; }           
67.             set { supplier_ContactTitle = value; }
68.         }
69.         
70.         [Column("Address", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
71.         public string Supplier_Address
72.         {
73.             get { return supplier_Address; }            
74.             set { supplier_Address = value; }
75.         }
76.         
77.         [Column("City", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
78.         public string Supplier_City
79.         {
80.             get { return supplier_City; }           
81.             set { supplier_City = value; }
82.         }
83.         
84.         [Column("Region", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
85.         public string Supplier_Region
86.         {
87.             get { return supplier_Region; }         
88.             set { supplier_Region = value; }
89.         }
90.         
91.         [Column("PostalCode", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
92.         public string Supplier_PostalCode
93.         {
94.             get { return supplier_PostalCode; }         
95.             set { supplier_PostalCode = value; }
96.         }
97.         
98.         [Column("Country", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
99.         public string Supplier_Country
100.         {
101.             get { return supplier_Country; }            
102.             set { supplier_Country = value; }
103.         }
104.         
105.         [Column("Phone", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
106.         public string Supplier_Phone
107.         {
108.             get { return supplier_Phone; }          
109.             set { supplier_Phone = value; }
110.         }
111.         
112.         [Column("Fax", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
113.         public string Supplier_Fax
114.         {
115.             get { return supplier_Fax; }            
116.             set { supplier_Fax = value; }
117.         }
118.         
119.         [Column("HomePage", Foreign = ProductsView.Supplier, ColumnMode = ColumnMode.Read)]
120.         public string Supplier_HomePage
121.         {
122.             get { return supplier_HomePage; }           
123.             set { supplier_HomePage = value; }
124.         }
125.         
126.         #endregion
127.     }

然后在使用的时候像下面这样：

1. dataGridView1.DataSource = new ProductsViewDAO().Search(null);

就可以显示所有ProductsView的内容。Products和ProductsView是通过CodeSmith生成，完全可以按照自己的需要修改。

ProductsDAO和ProductsViewDAO下次再介绍。