自定义代理类
1using System; 2using System.Data; 3 4namespace DataLayer 5{ 6 /**//// <summary> 7 /// This class strictly forwards every call to a subject object. To 8 /// intercept any specific call, create a subclass. 9 /// </summary> 10 public class DataReaderProxy : IDataReader 11 { 12 private IDataReader _subject; 13 /**//// <summary> 14 /// Create a proxy for the given subject. 15 /// </summary> 16 /// <param name="subject">The real reader to proxy for</param> 17 public DataReaderProxy(IDataReader subject) 18 { 19 _subject = subject; 20 } 21 // properties for IDataRecord 22 public virtual int FieldCount 23 { 24 get 25 { 26 return _subject.FieldCount; 27 } 28 } 29 public virtual object this [string name] 30 { 31 get 32 { 33 return _subject[name]; 34 } 35 } 36 public virtual object this [int index] 37 { 38 get 39 { 40 return _subject[index]; 41 } 42 } 43 // properties for IDataReader 44 public virtual int Depth 45 { 46 get 47 { 48 return _subject.Depth; 49 } 50 } 51 public virtual bool IsClosed 52 { 53 get 54 { 55 return _subject.IsClosed; 56 } 57 } 58 // methods for IDataRecord 59 public virtual bool GetBoolean(int i) 60 { 61 return _subject.GetBoolean(i); 62 } 63 public virtual byte GetByte(int i) 64 { 65 return _subject.GetByte(i); 66 } 67 public virtual long GetBytes( 68 int i, 69 long fieldoffset, 70 byte[] buffer, 71 int bufferoffset, 72 int length 73 ) 74 { 75 return _subject.GetBytes(i, fieldoffset, buffer, bufferoffset, length); 76 } 77 public virtual char GetChar(int i) 78 { 79 return _subject.GetChar(i); 80 } 81 public virtual long GetChars( 82 int i, 83 long fieldoffset, 84 char[] buffer, 85 int bufferoffset, 86 int length 87 ) 88 { 89 return _subject.GetChars(i, fieldoffset, buffer, bufferoffset, length); 90 } 91 public virtual IDataReader GetData(int i) 92 { 93 return _subject.GetData(i); 94 } 95 public virtual string GetDataTypeName(int i) 96 { 97 return _subject.GetDataTypeName(i); 98 } 99 public virtual DateTime GetDateTime(int i) 100 {101 return _subject.GetDateTime(i);102 }103 public virtual decimal GetDecimal(int i) 104 {105 return _subject.GetDecimal(i);106 }107 public virtual double GetDouble(int i) 108 {109 return _subject.GetDouble(i);110 }111 public virtual Type GetFieldType(int i) 112 {113 return _subject.GetFieldType(i);114 }115 public virtual float GetFloat(int i) 116 {117 return _subject.GetFloat(i);118 }119 public virtual Guid GetGuid(int i) 120 {121 return _subject.GetGuid(i);122 }123 public virtual short GetInt16(int i) 124 {125 return _subject.GetInt16(i);126 }127 public virtual int GetInt32(int i) 128 {129 return _subject.GetInt32(i);130 }131 public virtual long GetInt64(int i) 132 {133 return _subject.GetInt64(i);134 }135 public virtual string GetName(int i) 136 {137 return _subject.GetName(i);138 }139 public virtual int GetOrdinal(string name) 140 {141 return _subject.GetOrdinal(name);142 }143 public virtual string GetString(int i) 144 {145 return _subject.GetString(i);146 }147 public virtual object GetValue(int i) 148 {149 return _subject.GetValue(i);150 }151 public virtual int GetValues(object [] values) 152 {153 return _subject.GetValues(values);154 }155 public virtual bool IsDBNull(int i)156 {157 return _subject.IsDBNull(i);158 }159 // methods for IDataReader160 public virtual int RecordsAffected161 {162 get163 {164 return _subject.RecordsAffected;165 }166 }167 public virtual void Close()168 {169 _subject.Close();170 }171 public virtual DataTable GetSchemaTable()172 {173 return _subject.GetSchemaTable();174 }175 public virtual bool NextResult()176 {177 return _subject.NextResult();178 }179 public virtual bool Read()180 {181 return _subject.Read();182 }183 // methods for IDisposable184 public virtual void Dispose()185 {186 _subject.Dispose();187 }188 }189}
重写的特别代理
1using System; 2using System.Data; 3using DataLayer; 4 5/**//// <summary> 6/// Show that we know get our hooks into access to a data reader 7/// </summary> 8public class LimitingReader : DataReaderProxy 9{10 /**//// <summary>11 /// Just here to capture the subject12 /// </summary>13 /// <param name="subject">the reader we are a proxy for</param>14 public LimitingReader(IDataReader subject) : base (subject)15 {16 }17 /**//// <summary>18 /// Show that we can intercept requests for apogee information.19 /// </summary>20 public override object this [string name]21 {22 get23 {24 if (String.Compare(name, "apogee", true) == 0) // same 25 {26 return 0;27 }28 else 29 {30 return base [name];31 }32 }33 }34}
DataService类
1using System; 2using System.Data; 3using System.Data.OleDb; 4using System.Reflection; 5using System.IO; 6 7namespace Gof.Test.Proxy 8{ 9 public delegate object BorrowReader(IDataReader reader);10 public class DataService11 {12 public DataService()13 {}14 public static object GetDataReader(string sel,BorrowReader borrow)15 {16 try17 {18 using(OleDbConnection con = CreateConnection())19 {20 con.Open();21 OleDbCommand com = new OleDbCommand();22 com.Connection = con;23 com.CommandText = sel;24 OleDbDataReader reader = com.ExecuteReader();25 return borrow(reader);26 }27 }28 catch(Exception ex)29 {30 throw ex;//不处理了31 }32 }33 public static OleDbConnection CreateConnection()34 {35 string fileName = GetFileName("db","oozinoz.mdb");36 OleDbConnection con = new OleDbConnection();37 con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + fileName;38 return con;39 }40 public static String GetFileName(String dirName, String fileName)41 {42 String path;43 // Can we find the file using the OOZINOZ environment variable?44 String oozinozBase = Environment.GetEnvironmentVariable("OOZINOZ");45 if (oozinozBase != null) 46 {47 path = Path.Combine(Path.Combine(oozinozBase, dirName), fileName);48 if (File.Exists(path))49 {50 return path;51 }52 }53 // How 'bout relative to where the bin files are?54 Assembly a = Assembly.GetAssembly(typeof(DataService));55 DirectoryInfo thisDir = Directory.GetParent(a.Location);56 DirectoryInfo parentDir = Directory.GetParent(thisDir.FullName);57 path = Path.Combine(58 parentDir.FullName, 59 dirName + Path.DirectorySeparatorChar + fileName);60 if (File.Exists(path))61 {62 return path;63 }64 // Ok, how 'bout in the top-level directory?65 path = Path.Combine(Path.Combine(@"\ConsoleApplication2", dirName), fileName);66 if (File.Exists(path))67 {68 return path;69 }70 // dang71 throw new Exception("FileFinder.GetFileName() cannot find " + fileName + " in directory " + dirName);7273 }74 }75}
客户代码
1 string sel = "SELECT * FROM ROCKET"; 2 Gof.Test.Proxy.DataService.GetDataReader(sel, new Gof.Test.Proxy.BorrowReader(GetNames)); 3 4 private static Object GetNames(System.Data.IDataReader reader) 5 { 6 System.Data.IDataReader proxy = new LimitingReader(reader); 7 while (proxy.Read()) 8 { 9 Console.Write("{0,10} ", proxy["Name"]);10 Console.Write("{0,7:C} ", proxy["price"]);11 Console.Write("{0,5}", proxy["apogee"]);12 Console.WriteLine();13 }14 Console.ReadLine();15 return null;16 }
转载于:https://www.cnblogs.com/nanshouyong326/archive/2007/01/05/613108.html
相关资源：数据结构—成绩单生成器
