HashTable和HashSet中的类型陷阱

 1     Stopwatch st = new Stopwatch();//计时器
 2             Hashtable queryTable = TopK.GetHashtable();//获得HashTable
 3             HashSet<string> test = new HashSet<string>();
 4             string path = "dic.txt";
 5             if (File.Exists(path))
 6             {
 7 
 8                 using (StreamReader sr = new StreamReader(path, System.Text.Encoding.Default))
 9                 {
10                     string s = string.Empty;
11                     while (!string.IsNullOrEmpty(s = sr.ReadLine()))
12                     {
13                         test.Add(s);
14                     }
15                 }
16             }//创建过滤字典
17             Hashtable queryTable2 = new Hashtable();
18             List<string> teststring = new List<string>();
19             var aa = teststring[0];
20             foreach (var key in queryTable.Keys)//对Hashtable中的key进行过滤
21             {
22 
23                 if (!test.Contains(key))
24                 {
25                     queryTable2.Add(key, queryTable[key]);
26                 }
27              
28             }
29             st.Stop();
30             Console.WriteLine(st.ElapsedMilliseconds);
31             Console.Read();

1    foreach (var key in queryTable.Keys)//对Hashtable中的key进行过滤
2             {
3 
4                 if (!test.Contains(key))
5                 {
6                     queryTable2.Add(key, queryTable[key]);
7                 }
8              
9             }

1       foreach (string key in queryTable.Keys)//对Hashtable中的key进行过滤
2             {
3 
4                 if (!test.Contains(key))
5                 {
6                     queryTable2.Add(key, queryTable[key]);
7                 }
8              
9             }

1 public virtual void Add (
2     Object key,
3     Object value
4 )

 1     IL_00a4: ldloc.s CS$5$0001
 2                 IL_00a6: callvirt instance object [mscorlib]System.Collections.IEnumerator::get_Current()
 3                 IL_00ab: stloc.s key
 4                 IL_00ad: nop
 5                 IL_00ae: ldloc.2
 6                 IL_00af: ldloc.s key
 7                 IL_00b1: call bool [System.Core]System.Linq.Enumerable::Contains<object>(class [mscorlib]System.Collections.Generic.IEnumerable`10>, !!0)
 8                 IL_00b6: stloc.s CS$4$0000
 9                 IL_00b8: ldloc.s CS$4$0000
10                 IL_00ba: brtrue.s IL_00d0

 1             IL_00a4: ldloc.s CS$5$0001
 2                 IL_00a6: callvirt instance object [mscorlib]System.Collections.IEnumerator::get_Current()
 3                 IL_00ab: castclass [mscorlib]System.String
 4                 IL_00b0: stloc.s key
 5                 IL_00b2: nop
 6                 IL_00b3: ldloc.2
 7                 IL_00b4: ldloc.s key
 8                 IL_00b6: callvirt instance bool class [System.Core]System.Collections.Generic.HashSet`1<string>::Contains(!0)
 9                 IL_00bb: stloc.s CS$4$0000
10                 IL_00bd: ldloc.s CS$4$0000
11                 IL_00bf: brtrue.s IL_00d5