整理C#LinQ2012-10-09

手动使用linq对象

1,创建model对象,studentDB.cs

View Code

  1 #region Using directives

  2 using System;

  3 using System.Collections.Generic;

  4 using System.Linq;

  5 using System.Text;

  6 using System.Data.Linq.Mapping;

  7 using System.Data.Linq;

  8 using System.Configuration;

  9 #endregion

 10 

 11 

 12 namespace CSLinqToSQL.Manual

 13 {

 14     [Table(Name = "Person")]

 15     public class Student

 16     {

 17         public Student()

 18         {

 19             this._Grades = new EntitySet<CourseGrade>();

 20 

 21             // Set the default value of the column PersonCategory

 22             this.PersonCategory = 1;

 23         }

 24 

 25         // Refer to the ID column in database.

 26         [Column(IsPrimaryKey = true, Name = "PersonID", IsDbGenerated = true,

 27             AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY")]

 28         public int PersonID

 29         {

 30             get;

 31             set;

 32         }

 33 

 34         // Refer to the LastName column in database

 35         [Column]

 36         public string LastName

 37         {

 38             get;

 39             set;

 40         }

 41 

 42         // Refer to the FirstName column in database

 43         [Column]

 44         public string FirstName

 45         {

 46             get;

 47             set;

 48         }

 49 

 50         // Refer to the EnrollmentDate column in database

 51         [Column]

 52         public System.Nullable<System.DateTime> EnrollmentDate

 53         {

 54             get;

 55             set;

 56         }

 57 

 58         // Refer to the PersonCategory column in database

 59         [Column]

 60         public short PersonCategory

 61         {

 62             get;

 63             set;

 64         }

 65 

 66         // Refer to the FK of FK_CourseGrade_Student 

 67         private EntitySet<CourseGrade> _Grades;

 68         [Association(Storage = "_Grades", OtherKey = "StudentID")]

 69         public EntitySet<CourseGrade> CourseGrades

 70         {

 71             get { return this._Grades; }

 72             set { this._Grades.Assign(value); }

 73         }

 74 

 75         // Refer to the image column in database

 76         [Column(Name = "Picture")]

 77         public Byte[] Picture

 78         {

 79             get;

 80             set;

 81         }

 82     }

 83 

 84     [Table(Name = "Course")]

 85     public class Course

 86     {

 87         public Course()

 88         {

 89             this._Grades = new EntitySet<CourseGrade>();

 90         }

 91 

 92         // Refer to the CourseID column in database

 93         [Column(IsPrimaryKey = true, Name = "CourseID")]

 94         public int CourseID

 95         {

 96             get;

 97             set;

 98         }

 99 

100         // Refer to the Title column in database

101         [Column(Name = "Title")]

102         public string Title

103         {

104             get;

105             set;

106         }

107 

108         // Refer to the Credits column in database

109         [Column]

110         public int Credits

111         {

112             get;

113             set;

114         }

115 

116         // Refer to the FK for FK_CourseGrade_Course

117         private EntitySet<CourseGrade> _Grades;

118         [Association(Storage = "_Grades", OtherKey = "CourseID")]

119         public EntitySet<CourseGrade> Grades

120         {

121             get { return this._Grades; }

122             set { this._Grades.Assign(value); }

123         }

124     }

125 

126     [Table(Name = "CourseGrade")]

127     public class CourseGrade

128     {

129         public CourseGrade()

130         {

131             this._Course = default(EntityRef<Course>);

132             this._Student = default(EntityRef<Student>);

133         }

134 

135         // Refer to the EnrollmentID column in database

136         [Column(IsPrimaryKey = true, Name = "EnrollmentID", IsDbGenerated = true)]

137         public int EnrollmentID

138         {

139             get;

140             set;

141         }

142 

143         // Refer to the CourseID column in database

144         [Column(Name = "CourseID")]

145         public int CourseID

146         {

147             get;

148             set;

149         }

150 

151         // Refer to the StudentID column in database

152         [Column(Name = "StudentID")]

153         public int StudentID

154         {

155             get;

156             set;

157         }

158 

159         // Refer to the Grade column in database

160         [Column]

161         public decimal Grade

162         {

163             get;

164             set;

165         }

166 

167         // Refer to the FK of FK_CourseGrade_Course

168         private EntityRef<Course> _Course;

169         [Association(Storage = "_Course", ThisKey = "CourseID")]

170         public Course Course

171         {

172             get { return this._Course.Entity; }

173             set { this._Course.Entity = value; }

174         }

175 

176         // Refer to the FK of FK_CourseGrade_Student 

177         private EntityRef<Student> _Student;

178         [Association(Storage = "_Student", ThisKey = "StudentID")]

179         public Student Student

180         {

181             get { return this._Student.Entity; }

182             set { this._Student.Entity = value; }

183         }

184     }

185 

186     public class SchoolDataContext : DataContext

187     {

188         public Table<Student> Students;

189         public Table<Course> Courses;

190         public Table<CourseGrade> CourseGrades;

191         public SchoolDataContext(string connection) : base(connection) { }

192     }

193 }

2,手动操作

View Code

  1 /// <summary>

  2     /// 读取图片路径转换成字节数

  3     /// </summary>

  4     /// <param name="path">The path of the image file.</param>

  5     /// <returns>The output of the array.</returns>

  6     private static byte[] ReadImage(string path)

  7     {

  8         try

  9         {

 10             // Open the image file

 11             using (FileStream fs = new FileStream(path, FileMode.Open,

 12                 FileAccess.Read))

 13             {

 14                 // Create an array of bytes

 15                 byte[] bPicture = new byte[fs.Length];

 16 

 17                 // Read the image file

 18                 fs.Read(bPicture, 0, Convert.ToInt32(fs.Length));

 19 

 20                 return bPicture;

 21             }

 22         }

 23         catch (Exception ex)

 24         {

 25             Console.WriteLine(

 26                 "The application throws the error: {0}", ex.Message);

 27             return null;

 28         }

 29     }

 30  /// <summary>

 31     /// 下面的方法适用于手动创建的类

 32     /// </summary>

 33     private static void QueryDBByManuallyCreatedClasses()

 34     {

 35         Console.WriteLine("Query using the manually-created classes.");

 36         try

 37         {

 38             string connStr = ConfigurationManager.ConnectionStrings[

 39                 "SQLServer2005DB"].ConnectionString;

 40 

 41             // DataContext takes a connection string

 42             CSLinqToSQL.Manual.SchoolDataContext db = new

 43                 CSLinqToSQL.Manual.SchoolDataContext(connStr);

 44             Console.WriteLine("\nAdd a new student to the Person table");

 45 

 46 

 47             // 创建一个新学生。

 48             // 我们不需要在此处设置的 PersonCategory 值，如果我们想要

 49             // 默认值将设置为此数据库中的列。

 50             CSLinqToSQL.Manual.Student student = new CSLinqToSQL.Manual.Student

 51             {

 52                 FirstName = "Rongchun",

 53                 LastName = "Zhang",

 54                 EnrollmentDate = DateTime.Now,

 55                 Picture = ReadImage(@"MSDN.jpg"),

 56             };

 57 

 58             // 添加一个新对象到学生表

 59             db.Students.InsertOnSubmit(student);

 60 

 61             // 提交数据

 62             db.SubmitChanges();

 63 

 64             // 查询学生

 65             Console.WriteLine("\nQuery students whose first name is Roger:");

 66             var students = from p in db.Students

 67                            where p.FirstName == "Roger"

 68                            select p;

 69 

 70             foreach (var p in students)

 71                 Console.WriteLine("ID = {0}, Name = {1} {2}", p.PersonID,

 72                     p.FirstName, p.LastName);

 73 

 74             // 连表查询

 75             Console.WriteLine("\nQuery max. grade of each course:");

 76             var courses =

 77                 from grade in db.CourseGrades

 78                 group grade by grade.CourseID into g

 79                 join cur in db.Courses on g.Key equals cur.CourseID

 80                 select new

 81                 {

 82                     CourseID = g.Key,

 83                     Title = cur.Title,

 84                     TopGrade = g.Max(gra => gra.Grade)

 85                 };

 86 

 87             foreach (var c in courses)

 88                 Console.WriteLine("Course = {0}, TopGrade = {1}",

 89                     c.Title, c.TopGrade);

 90 

 91             Console.WriteLine("\nQuery all grades that Nino got");

 92 

 93             var grades =

 94                from stu in db.Students

 95                from gra in stu.CourseGrades

 96                join cur in db.Courses on gra.CourseID equals cur.CourseID

 97                where stu.FirstName == "Nino"

 98                select new

 99                {

100                    Stduent = stu,

101                    Course = cur,

102                    CourseGrade = gra

103                };

104 

105             foreach (var grade in grades)

106             {

107                 Console.WriteLine("FirstName = {0}, Course= {1}, Grade= {2}",

108                     grade.Stduent.FirstName,

109                     grade.Course.Title,

110                     grade.CourseGrade.Grade);

111             }

112         }

113         catch (Exception e)

114         {

115             Console.WriteLine("The application throws the error: {0}", e.Message);

116         }

117     }