String PK StringBuilder,传说就是传说，只有动手实验，才能得出确定的答案

本机测试结果如下：

大部分情况下，string 性能并不比StringBuilder差，只有特殊情况才出现差异，并非如前面有些朋友测试的结果哪样，只要使用StringBuilder 就一定比String表现优异。

另外，大多数测试者都没有考虑内存分配的时间与成本（因为大多数的内存都比较在>2G)。

本次测试也只考虑时间运行效率，没有考虑空间成本

本次测试条件：.net 4.0 硬件：Tinkpad t540P,4G内存 win8.1

第一种方法：

  1 [TestClass]
  2     public class StringTest1
  3     {
  4         [TestMethod]
  5         public void String1Test1()
  6         {
  7             for (int i = 0; i < 1; i++)
  8             {
  9                 string queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
10                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
11                 queryString += " order by p.Name ";
12             }
13         }
14         [TestMethod]
15         public void String10Test1()
16         {
17             for (int i = 0; i < 10; i++)
18             {
19                 string queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
20                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
21                 queryString += " order by p.Name ";
22             }
23         }
24         [TestMethod]
25         public void String100Test1()
26         {
27             for (int i = 0; i < 100; i++)
28             {
29                 string queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
30                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
31                 queryString += " order by p.Name ";
32             }
33         }
34         [TestMethod]
35         public void String1000Test1()
36         {
37             for (int i = 0; i < 1000; i++)
38             {
39                 string queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
40                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
41                 queryString += " order by p.Name ";
42             }
43         }
44         [TestMethod]
45         public void String10000Test1()
46         {
47             for (int i = 0; i < 10000; i++)
48             {
49                 string queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
50                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
51                 queryString += " order by p.Name ";
52             }
53         }
54
55         [TestMethod]
56         public void StringBuilder1Test1()
57         {
58             for (int i = 0; i < 1; i++)
59             {
60                 StringBuilder ssb = new StringBuilder();
61                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
62                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
63                 ssb.Append(" order by p.Name ");
64             }
65         }
66         [TestMethod]
67         public void StringBuilder10Test1()
68         {
69             for (int i = 0; i < 10; i++)
70             {
71                 StringBuilder ssb = new StringBuilder();
72                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
73                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
74                 ssb.Append(" order by p.Name ");
75             }
76         }
77         [TestMethod]
78         public void StringBuilder100Test1()
79         {
80             for (int i = 0; i < 100; i++)
81             {
82                 StringBuilder ssb = new StringBuilder();
83                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
84                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
85                 ssb.Append(" order by p.Name ");
86             }
87         }
88         [TestMethod]
89         public void StringBuilder1000Test1()
90         {
91             for (int i = 0; i < 1000; i++)
92             {
93                 StringBuilder ssb = new StringBuilder();
94                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
95                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
96                 ssb.Append(" order by p.Name ");
97             }
98         }
99         [TestMethod]
100         public void StringBuilder10000Test1()
101         {
102             for (int i = 0; i < 10000; i++)
103             {
104                 StringBuilder ssb = new StringBuilder();
105                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
106                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
107                 ssb.Append(" order by p.Name ");
108             }
109         }
110     }

View Code

第二种方法

  1 [TestClass]
  2     public class StringTest2
  3     {
  4         [TestMethod]
  5         public void String1Test2()
  6         {
  7             string queryString = string.Empty;
  8             for (int i = 0; i < 1; i++)
  9             {
10                 queryString = string.Empty;
11                 queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
12                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
13                 queryString += " order by p.Name ";
14             }
15         }
16         [TestMethod]
17         public void String10Test2()
18         {
19             string queryString = string.Empty;
20             for (int i = 0; i < 10; i++)
21             {
22                 queryString = string.Empty;
23                 queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
24                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
25                 queryString += " order by p.Name ";
26             }
27         }
28         [TestMethod]
29         public void String100Test2()
30         {
31             string queryString = string.Empty;
32             for (int i = 0; i < 100; i++)
33             {
34                 queryString = string.Empty;
35                 queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
36                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
37                 queryString += " order by p.Name ";
38             }
39         }
40         [TestMethod]
41         public void String1000Test2()
42         {
43             string queryString = string.Empty;
44             for (int i = 0; i < 1000; i++)
45             {
46                 queryString = string.Empty;
47                 queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
48                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
49                 queryString += " order by p.Name ";
50             }
51         }
52         [TestMethod]
53         public void String10000Test2()
54         {
55             string queryString = string.Empty;
56             for (int i = 0; i < 10000; i++)
57             {
58                 queryString = string.Empty;
59                 queryString = @"select p from DALParty as p where p.OwnerID=:OwnerID";
60                 queryString += " and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)";
61                 queryString += " order by p.Name ";
62             }
63         }
64
65         [TestMethod]
66         public void StringBuilder1Test2()
67         {
68             StringBuilder ssb = new StringBuilder();
69             for (int i = 0; i < 1; i++)
70             {
71                 ssb.Clear();
72                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
73                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
74                 ssb.Append(" order by p.Name ");
75             }
76         }
77         [TestMethod]
78         public void StringBuilder10Test2()
79         {
80             StringBuilder ssb = new StringBuilder();
81             for (int i = 0; i < 10; i++)
82             {
83                 ssb.Clear();
84                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
85                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
86                 ssb.Append(" order by p.Name ");
87             }
88         }
89         [TestMethod]
90         public void StringBuilder100Test2()
91         {
92             StringBuilder ssb = new StringBuilder();
93             for (int i = 0; i < 100; i++)
94             {
95                 ssb.Clear();
96                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
97                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
98                 ssb.Append(" order by p.Name ");
99             }
100         }
101         [TestMethod]
102         public void StringBuilder1000Test2()
103         {
104             StringBuilder ssb = new StringBuilder();
105             for (int i = 0; i < 1000; i++)
106             {
107                 ssb.Clear();
108                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
109                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
110                 ssb.Append(" order by p.Name ");
111             }
112         }
113         [TestMethod]
114         public void StringBuilder10000Test2()
115         {
116             StringBuilder ssb = new StringBuilder();
117             for (int i = 0; i < 10000; i++)
118             {
119                 ssb.Clear();
120                 ssb.Append(@"select p from DALParty as p where p.OwnerID=:OwnerID");
121                 ssb.Append(" and (p.Name like :Name  or p.Code like :Name or p.TaxCode like :Name)");
122                 ssb.Append(" order by p.Name ");
123             }
124         }
125     }

View Code

测试结果如下：

根据测试结果如下：

如果字符串拼接次数很小 <= 1000次，两者性能几乎没有差别，只有在字符本身长度大，拼接次数很大的情况下，使用StringBuilder才有意义。

通过第二次方法测试可表明，在循环体内每次 new StringBuilder 时，是非常耗时的工作，并且new时预分配内存，也是占内存的，有时并没有使用到。

因此：使用string 还是 StringBuilder 还要看使用环境。

在大部分情况下，string 并不会对性能造成损失，使用string 即方便，也经济，仍然是字符串操作的首先。