(原創) 如何建立自己的Collection? (.NET) (C#) (C++/CLI) (C/C++)
Abstract
在OO設計中，對應於Relational Database的一筆資料，我們會用一個object，如Customer，但多筆資料呢?有些人會用DataSet，有些人會用List<Customer>，這些方法都不錯，但若要設計自己的Collection：Customers type，那該怎麼做呢?
Introduction
使用DataSet(DataTable,DataReader....)或List<Customer>這些代表Collection，理論上並沒有什麼錯，事實上很多人也都這樣用，缺點就是比較沒有OO的flavor。理想上，既然有Customer class代表一筆資料，就應該有Customers class代表多筆資料，而N-Tiers間的傳輸應該是Customers collection，而非DataSet或List<Customer>。
要產生自己的Collection，有兩種方式，一個是.NET 1.0的方式，一個是.NET 2.0的方式。
.NET 1.0方式(在.NET 2.0仍然可以使用)
繼承CollectionBase，CollectionBase是一個abstract class，implement了IList ，ICollection，IEnumerable，已經為Collection做好了基礎架構，我們要做的就是overload this[]、IndexOf()、Add()、Remove()就好，其他的事情，CollectionBase已經幫我們做好了。
C#
1
/*
2
(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : BuildOwnCollection1.cs
5Compiler : Visual Studio 2005 / C# 2.0
6Description : Demo how to build strong typed collection
7Release : 06/19/2007 1.0
8
*/
9
using System;
10using System.Collections;
11
12public class Member {
13 private string _name;
14
15
public Member() {}
16 public Member(string name) {
17 _name = name;
18
}
19
20 public string Name {
21 get { return _name;}
22 set { _name = value;}
23 }
24
25 public override bool Equals(object obj) {
26 Member member = (Member)obj;
27 return (_name == member.Name) ? true : false;
28 }
29
30 public override int GetHashCode() {
31 return base.GetHashCode();
32 }
33
34 public static bool operator ==(Member member1, Member member2) {
35 return member1.Equals(member2) ? true : false;
36 }
37
38 public static bool operator !=(Member member1, Member member2) {
39 return !(member1 == member2);
40 }
41}
42
43public class Members : CollectionBase {
44 public Member this[int index] {
45 get { return (Member)List[index]; }
46 set { List[index] = value; }
47 }
48
49 public int IndexOf(Member member) {
50 return this.List.IndexOf(member);
51 }
52
53 public void Add(Member member) {
54 this.List.Add(member);
55 }
56
57 public void Remove(Member member) {
58 if (this.IndexOf(member) != -1)
59 List.Remove(member);
60 }
61}
62
63public class main {
64 public static void Main() {
65 Members members = new Members();
66
67 // insert
68 members.Add(new Member("Clare"));
69 members.Add(new Member("Jessie"));
70 members.Add(new Member("Jingyi"));
71
72 // modify
73 int index = members.IndexOf(new Member("Jessie"));
74 if (index != -1) members[index] = new Member("Cerlina");
75
76 // delete
77 members.Remove(new Member("Clare"));
78
79 // search
80 index = members.IndexOf(new Member("Jingyi"));
81 if (index != -1) members.RemoveAt(index);
82
83 foreach(Member member in members) {
84 Console.WriteLine(member.Name);
85 }
86 }
87}
/* 
2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : BuildOwnCollection1.cs5
Compiler : Visual Studio 2005 / C# 2.06
Description : Demo how to build strong typed collection 7
Release : 06/19/2007 1.08
*/9
using System;10
using System.Collections;11
12
public class Member {
13
private string _name;14
15
public Member() {}
16
public Member(string name) {17
_name = name;18
}19
20
public string Name {21
get { return _name;}22
set { _name = value;}23
}24
25
public override bool Equals(object obj) {26
Member member = (Member)obj;27
return (_name == member.Name) ? true : false;28
}29
30
public override int GetHashCode() {31
return base.GetHashCode();32
}33
34
public static bool operator ==(Member member1, Member member2) {35
return member1.Equals(member2) ? true : false;36
}37
38
public static bool operator !=(Member member1, Member member2) {39
return !(member1 == member2);40
}41
}42
43
public class Members : CollectionBase {44
public Member this[int index] {45
get { return (Member)List[index]; }46
set { List[index] = value; }47
}48
49
public int IndexOf(Member member) {50
return this.List.IndexOf(member);51
}52
53
public void Add(Member member) {54
this.List.Add(member);55
}56
57
public void Remove(Member member) {58
if (this.IndexOf(member) != -1) 59
List.Remove(member);60
}61
}62
63
public class main {64
public static void Main() {65
Members members = new Members();66
67
// insert 68
members.Add(new Member("Clare"));69
members.Add(new Member("Jessie"));70
members.Add(new Member("Jingyi"));71
72
// modify73
int index = members.IndexOf(new Member("Jessie"));74
if (index != -1) members[index] = new Member("Cerlina");75
76
// delete77
members.Remove(new Member("Clare"));78
79
// search80
index = members.IndexOf(new Member("Jingyi"));81
if (index != -1) members.RemoveAt(index);82
83
foreach(Member member in members) {84
Console.WriteLine(member.Name);85
}86
}87
}
執行結果
Cerlina
在Member class中，25行到40行
public override bool Equals(object obj) { Member member = (Member)obj; return (_name == member.Name) ? true : false;}public override int GetHashCode() { return base.GetHashCode();}public static bool operator ==(Member member1, Member member2) { return member1.Equals(member2) ? true : false;}public static bool operator !=(Member member1, Member member2) { return !(member1 == member2);}
整體的目標是為了改寫object的比較方式，在.NET，預設是用reference比較object是否相同，但這對Collection的IndexOf()，Remove()有很大的影響，所以我override了Equals()和GetHashCode()，並對==和!=做了operator overloading。
CollectionBase原本都有實現IndexOf()，Add()，Remove()，但因只針對Object而非Member，所以針對了Member overload了IndexOf()，Add()，Remove()，另外使用了indexer是為了方便Collection的使用。
C++/CLI
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : BuildOwnCollection1.cpp
5Compiler : Visual C++ 8.0 / C++/CLI
6Description : Demo how to build strong typed collection
7Release : 06/19/2007 1.0
8*/
9#include "stdafx.h"
10
11using namespace System;
12using namespace System::Collections;
13
14public ref class Member {
15private:
16 String^ _name;
17
18public:
19 Member() {}
20 Member(String^ name) {
21 _name = name;
22 }
23
24 property String^ Name {
25 String^ get() { return _name;}
26 void set(String^ value) { _name = value; }
27 }
28
29 virtual bool Equals(Object^ obj) override {
30 Member^ member = safe_cast<Member^>(obj);
31 return (_name == member->Name) ? true : false;
32 }
33
34 virtual int GetHashCode() override {
35 return Object::GetHashCode();
36 }
37
38 static bool operator==(Member^ member1, Member^ member2) {
39 return member1->Equals(member2) ? true : false;
40 }
41
42 static bool operator!=(Member^ member1, Member^ member2) {
43 return !(member1 == member2);
44 }
45};
46
47public ref class Members : CollectionBase {
48public:
49 property Member^ default[int] {
50 Member^ get(int index) { return safe_cast<Member^>(List[index]); }
51 void set(int index, Member^ value) { List[index] = safe_cast<Member^>(value); }
52 }
53
54 int IndexOf(Member^ member) {
55 return this->List->IndexOf(member);
56 }
57
58 void Add(Member^ member) {
59 this->List->Add(member);
60 }
61
62 void Remove(Member^ member) {
63 if (this->IndexOf(member) != -1)
64 List->Remove(member);
65 }
66};
67
68int main() {
69 Members^ members = gcnew Members;
70
71 // insert
72 members->Add(gcnew Member("Clare"));
73 members->Add(gcnew Member("Jessie"));
74 members->Add(gcnew Member("Jingyi"));
75
76 // modify
77 int index = members->IndexOf(gcnew Member("Jessie"));
78 if (index != -1)
79 members[index] = gcnew Member("Cerlina");
80
81 // delete
82 members->Remove(gcnew Member("Clare"));
83
84 // search
85 index = members->IndexOf(gcnew Member("Jingyi"));
86 if (index != -1) members->RemoveAt(index);
87
88 for each(Member^ member in members)
89 Console::WriteLine(member->Name);
90}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : BuildOwnCollection1.cpp5
Compiler : Visual C++ 8.0 / C++/CLI6
Description : Demo how to build strong typed collection 7
Release : 06/19/2007 1.08
*/9
#include "stdafx.h"10
11
using namespace System;12
using namespace System::Collections;13
14
public ref class Member {15
private:16
String^ _name;17
18
public:19
Member() {}20
Member(String^ name) {21
_name = name;22
}23
24
property String^ Name {25
String^ get() { return _name;}26
void set(String^ value) { _name = value; }27
}28
29
virtual bool Equals(Object^ obj) override {30
Member^ member = safe_cast<Member^>(obj);31
return (_name == member->Name) ? true : false;32
}33
34
virtual int GetHashCode() override {35
return Object::GetHashCode();36
}37
38
static bool operator==(Member^ member1, Member^ member2) {39
return member1->Equals(member2) ? true : false;40
}41
42
static bool operator!=(Member^ member1, Member^ member2) {43
return !(member1 == member2);44
}45
};46
47
public ref class Members : CollectionBase {48
public:49
property Member^ default[int] {50
Member^ get(int index) { return safe_cast<Member^>(List[index]); }51
void set(int index, Member^ value) { List[index] = safe_cast<Member^>(value); }52
}53
54
int IndexOf(Member^ member) {55
return this->List->IndexOf(member);56
}57
58
void Add(Member^ member) {59
this->List->Add(member);60
}61
62
void Remove(Member^ member) {63
if (this->IndexOf(member) != -1) 64
List->Remove(member);65
}66
};67
68
int main() {69
Members^ members = gcnew Members;70
71
// insert 72
members->Add(gcnew Member("Clare"));73
members->Add(gcnew Member("Jessie"));74
members->Add(gcnew Member("Jingyi"));75
76
// modify77
int index = members->IndexOf(gcnew Member("Jessie"));78
if (index != -1) 79
members[index] = gcnew Member("Cerlina");80
81
// delete82
members->Remove(gcnew Member("Clare"));83
84
// search85
index = members->IndexOf(gcnew Member("Jingyi"));86
if (index != -1) members->RemoveAt(index);87
88
for each(Member^ member in members)89
Console::WriteLine(member->Name);90
}
執行結果
Cerlina
.NET 2.0 (使用Collection<T>)
繼承Collection<Member>，因為是泛型，所以不用再overload IndexOf()，Add()，Remove()，也不用在定義indexer，因為泛型會直接使用Member，所以code非常精簡。
Collection<T>的架構頗複雜，implement了IEnumerable，IEnumerable<T>，ICollection，ICollection<T>，IList，IList<T>。
C#
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : BuildOwnCollection2.cs
5Compiler : Visual Studio 2005 / C# 2.0
6Description : Demo how to build strong typed collection
7Release : 06/19/2007 1.0
8*/
9using System;
10using System.Collections.ObjectModel;
11
12public class Member {
13 private string _name;
14
15 public Member() { }
16 public Member(string name) {
17 _name = name;
18 }
19
20 public string Name {
21 get { return _name; }
22 set { _name = value; }
23 }
24
25 public override bool Equals(object obj) {
26 Member member = (Member)obj;
27 return (_name == member.Name) ? true : false;
28 }
29
30 public override int GetHashCode() {
31 return base.GetHashCode();
32 }
33
34 public static bool operator ==(Member member1, Member member2) {
35 return member1.Equals(member2) ? true : false;
36 }
37
38 public static bool operator !=(Member member1, Member member2) {
39 return !(member1 == member2);
40 }
41}
42
43public class Members : Collection<Member> {
44}
45
46public class main {
47 public static void Main() {
48 Members members = new Members();
49
50 // insert
51 members.Add(new Member("Clare"));
52 members.Add(new Member("Jessie"));
53 members.Add(new Member("Jingyi"));
54
55 // modify
56 int index = members.IndexOf(new Member("Jessie"));
57 if (index != -1) members[index] = new Member("Cerlina");
58
59 // delete
60 members.Remove(new Member("Clare"));
61
62 // search
63 index = members.IndexOf(new Member("Jingyi"));
64 if (index != -1) members.RemoveAt(index);
65
66 foreach (Member member in members) {
67 Console.WriteLine(member.Name);
68 }
69 }
70}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : BuildOwnCollection2.cs5
Compiler : Visual Studio 2005 / C# 2.06
Description : Demo how to build strong typed collection 7
Release : 06/19/2007 1.08
*/9
using System;10
using System.Collections.ObjectModel;11
12
public class Member {13
private string _name;14
15
public Member() { }16
public Member(string name) {17
_name = name;18
}19
20
public string Name {21
get { return _name; }22
set { _name = value; }23
}24
25
public override bool Equals(object obj) {26
Member member = (Member)obj;27
return (_name == member.Name) ? true : false;28
}29
30
public override int GetHashCode() {31
return base.GetHashCode();32
}33
34
public static bool operator ==(Member member1, Member member2) {35
return member1.Equals(member2) ? true : false;36
}37
38
public static bool operator !=(Member member1, Member member2) {39
return !(member1 == member2);40
}41
}42
43
public class Members : Collection<Member> {44
}45
46
public class main {47
public static void Main() {48
Members members = new Members();49
50
// insert51
members.Add(new Member("Clare"));52
members.Add(new Member("Jessie"));53
members.Add(new Member("Jingyi"));54
55
// modify56
int index = members.IndexOf(new Member("Jessie"));57
if (index != -1) members[index] = new Member("Cerlina");58
59
// delete60
members.Remove(new Member("Clare"));61
62
// search63
index = members.IndexOf(new Member("Jingyi"));64
if (index != -1) members.RemoveAt(index);65
66
foreach (Member member in members) {67
Console.WriteLine(member.Name);68
}69
}70
}
執行結果
Cerlina
35行
public class Members : Collection<Member> {}
非常精簡，只需繼承Collection<Member>即可。
C++/CLI
1/*
2(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : BuildOwnCollection2.cpp
5Compiler : Visual C++ 8.0 / C++/CLI
6Description : Demo how to build strong typed collection by Generics
7Release : 06/19/2007 1.0
8*/
9#include "stdafx.h"
10
11using namespace System;
12using namespace System::Collections::ObjectModel;
13
14public ref class Member {
15private:
16 String^ _name;
17
18public:
19 Member() { }
20 Member(String^ name) {
21 _name = name;
22 }
23
24public:
25 property String^ Name {
26 String^ get() { return _name; }
27 void set(String^ value) { _name = value; }
28 }
29
30 virtual bool Equals(Object^ obj) override {
31 Member^ member = safe_cast<Member^>(obj);
32 return (_name == member->Name) ? true : false;
33 }
34
35 virtual int GetHashCode() override {
36 return Object::GetHashCode();
37 }
38
39 static bool operator ==(Member^ member1, Member^ member2) {
40 return member1->Equals(member2) ? true : false;
41 }
42
43 static bool operator !=(Member^ member1, Member^ member2) {
44 return !(member1 == member2);
45 }
46};
47
48public ref class Members : Collection<Member^> {
49};
50
51int main() {
52 Members^ members = gcnew Members;
53
54 // insert
55 members->Add(gcnew Member("Clare"));
56 members->Add(gcnew Member("Jessie"));
57 members->Add(gcnew Member("Jingyi"));
58
59 // modify
60 int index = members->IndexOf(gcnew Member("Jessie"));
61 if (index != -1) members[index] = gcnew Member("Cerlina");
62
63 // delete
64 members->Remove(gcnew Member("Clare"));
65
66 // search
67 index = members->IndexOf(gcnew Member("Jingyi"));
68 if (index != -1) members->RemoveAt(index);
69
70 for each (Member^ member in members) {
71 Console::WriteLine(member->Name);
72 }
73}
/* 2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : BuildOwnCollection2.cpp5
Compiler : Visual C++ 8.0 / C++/CLI6
Description : Demo how to build strong typed collection by Generics7
Release : 06/19/2007 1.08
*/9
#include "stdafx.h"10
11
using namespace System;12
using namespace System::Collections::ObjectModel;13
14
public ref class Member {15
private:16
String^ _name;17
18
public:19
Member() { }20
Member(String^ name) {21
_name = name;22
}23
24
public:25
property String^ Name {26
String^ get() { return _name; }27
void set(String^ value) { _name = value; }28
}29
30
virtual bool Equals(Object^ obj) override {31
Member^ member = safe_cast<Member^>(obj);32
return (_name == member->Name) ? true : false;33
}34
35
virtual int GetHashCode() override {36
return Object::GetHashCode();37
}38
39
static bool operator ==(Member^ member1, Member^ member2) {40
return member1->Equals(member2) ? true : false;41
}42
43
static bool operator !=(Member^ member1, Member^ member2) {44
return !(member1 == member2);45
}46
};47
48
public ref class Members : Collection<Member^> {49
};50
51
int main() {52
Members^ members = gcnew Members;53
54
// insert55
members->Add(gcnew Member("Clare"));56
members->Add(gcnew Member("Jessie"));57
members->Add(gcnew Member("Jingyi"));58
59
// modify60
int index = members->IndexOf(gcnew Member("Jessie"));61
if (index != -1) members[index] = gcnew Member("Cerlina");62
63
// delete64
members->Remove(gcnew Member("Clare"));65
66
// search67
index = members->IndexOf(gcnew Member("Jingyi"));68
if (index != -1) members->RemoveAt(index);69
70
for each (Member^ member in members) {71
Console::WriteLine(member->Name);72
}73
}
執行結果
Cerlina
Conclusion
泛型最基本的應用，也是最原始的應用，就是在container，若用OO，只能用多型(多態)的技術，讓container放Object type，進Container須轉型成Object，出Container需再轉回各type，若用泛型，就可直接將各type放進container，不需轉型，不只速度提升，且code也非常的精簡。
